On Sat, Mar 03, 2012 at 12:28:59AM -0800, Mike Turquette wrote:

The common clk framework provides clk_prepare and clk_unprepare implementations. Create an entry for HAVE_CLK_PREPARE so that COMMON_CLK can select it.

Signed-off-by: Mike Turquette mturquette@linaro.org Signed-off-by: Mike Turquette mturquette@ti.com Acked-by: Shawn Guo shawn.guo@linaro.org Cc: Jeremy Kerr jeremy.kerr@canonical.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Arnd Bergman arnd.bergmann@linaro.org Cc: Paul Walmsley paul@pwsan.com Cc: Richard Zhao richard.zhao@linaro.org Cc: Saravana Kannan skannan@codeaurora.org Cc: Magnus Damm magnus.damm@gmail.com Cc: Rob Herring rob.herring@calxeda.com Cc: Mark Brown broonie@opensource.wolfsonmicro.com Cc: Linus Walleij linus.walleij@stericsson.com Cc: Stephen Boyd sboyd@codeaurora.org Cc: Amit Kucheria amit.kucheria@linaro.org Cc: Deepak Saxena dsaxena@linaro.org Cc: Grant Likely grant.likely@secretlab.ca Cc: Andrew Lunn andrew@lunn.ch

---

drivers/clk/Kconfig | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig index 9b3cd08..3912576 100644 --- a/drivers/clk/Kconfig +++ b/drivers/clk/Kconfig @@ -8,3 +8,6 @@ config HAVE_CLK_PREPARE config HAVE_MACH_CLKDEV bool

+config HAVE_CLK_PREPARE

• bool

We've already had it. redundant?

Thanks Richard

-- 1.7.5.4

---

linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

On Tue, Mar 6, 2012 at 11:00 AM, Sascha Hauer s.hauer@pengutronix.de wrote:

On Mon, Mar 05, 2012 at 12:03:15PM -0800, Turquette, Mike wrote:

...

On Sun, Mar 4, 2012 at 11:38 PM, Sascha Hauer s.hauer@pengutronix.de wrote:

...

On Sun, Mar 04, 2012 at 04:12:21PM -0800, Turquette, Mike wrote:

...

...

...

I believe this patch already does what you suggest, but I might be missing your point.

In include/linux/clk-private.h you expose struct clk outside the core. This has to be done to make static initializers possible. There is a big warning in this file that it must not be included from files implementing struct clk_ops. You can simply avoid this warning by declaring struct clk with only a single member:

include/linux/clk.h:

struct clk {        struct clk_internal *internal; };

This way everybody knows struct clk (thus can embed it in their static initializers), but doesn't know anything about the internal members. Now in drivers/clk/clk.c you declare struct clk_internal exactly like struct clk was declared before:

struct clk_internal {        const char              *name;        const struct clk_ops    *ops;        struct clk_hw           *hw;        struct clk              *parent;        char                    **parent_names;        struct clk              **parents;        u8                      num_parents;        unsigned long           rate;        unsigned long           flags;        unsigned int            enable_count;        unsigned int            prepare_count;        struct hlist_head       children;        struct hlist_node       child_node;        unsigned int            notifier_count; #ifdef CONFIG_COMMON_CLK_DEBUG        struct dentry           *dentry; #endif };

An instance of struct clk_internal will be allocated in __clk_init/clk_register. Now the private data stays completely inside the core and noone can abuse it.

Hi Sascha,

I see the disconnect here.  For OMAP (and possibly other platforms) at least some clock data is necessary during early boot, before the regular allocation methods are available (timers for instance).

We had this problem on i.MX aswell. It turned out that the timer clock is the only clock that is needed so early. We solved this by moving the clock init to the system timer init function.

When you say "mov[ed] the clock init to the system timer init function" do you mean that you statically allocated struct clk and used the clk framework api, or instead you just did some direct register writes to initialize things properly?

I meant that on i.MX we do the clock tree initialization when kmalloc is available, see the attached patch for omap4 based on your branch which does the same for Omap. The first clock you need is the one for the timer, so you can initialize the clocktree at the beginning of time_init() and don't need statically initialized clocks anymore.

...

...

Well, the file is work in progress, you probably fix this before sending it out, but I bet people will include clk-private.h and nobody else notices it.

clock44xx_data.c does not violate that rule.  None of the logic that implements ops for those clocks is present clock44xx_data.c.

Indeed, I missed that. It only has the ops but not the individual functions.

...

All of the code in that file is simply initialization and registration of OMAP4 clocks.  Many of the clocks are basic clock types (divider, multiplexer and fixed-rate are used in that file) with protected code drivers/clk/clk-*.c and the remaining clocks are of the struct clk_hw_omap variety, which has code spread across several files:

arch/arm/mach-omap2/clock.c arch/arm/mach-omap2/clock.h arch/arm/mach-omap2/clkt_dpll.c arch/arm/mach-omap2/clkt_clksel.c arch/arm/mach-omap2/dpll3xxx.c arch/arm/mach-omap2/dpll4xxx.c

All of the above files include linux/clk-provider.h, not linux/clk-private.h.  That code makes heavy use of the __clk_get_whatever helpers and shows how a platform might honor the layer of separation between struct clk and stuct clk_ops/struct clk_foo.  You are correct that the code is a work-in-progress, but there are no layering violations that I can see.

I also think we are talking past each other to some degree.  One point I would like to make (and maybe you already know this from code review) is that it is unnecessary to have pointers to your parent struct clk*'s when either initializing or registering your clocks.  In fact the existing clk_register_foo functions don't even allow you to pass in parent pointers and rely wholly on string name matching.  I just wanted to point that out in case it went unnoticed, as it is a new way of doing things from the previous series and was born out of Thomas' review of V4 and multi-parent handling.  This also keeps device-tree in mind where we might not know the struct clk *pointer at compile time for "connecting" discrete devices.

Yes, I've seen this and I really like it. Also the change that multiplexers return an index to an array instead of the parent clock is very nice.

Sascha

8<-----------------------------------------------------

ARM omap4: move clocktree init to timer init time so we don't need static clocks

Signed-off-by: Sascha Hauer s.hauer@pengutronix.de

Hi Sascha,

Thanks for the example code. This is in fact something I had considered doing before, but it is a bit complicated for my platform.

We set up all of the OMAP clocks with __clk_init because this is a dependency of OMAP's hwmod code which models and interacts with specific resources for hardware modules, such as clocks. There are other dependencies such as our clockdomain code, which needs the clocks to be fully initialized. Some aspects of these layers get init'd before we can allocate memory.

Admittedly I think that the OMAP code could migrate some of these bits to a lazy-registration model, specifically the hwmod object instances, but that requires an awful lot of refactoring for a fairly large stack of platform code. This might be something to achieve in the future but for now we *need* initialisation to be fully static.

Assuming that some day OMAP code can be refactored to allow for lazy (or at least initcall-based) registration of clocks then perhaps your suggestion can take root. Which leads me to this question: are there any other platforms out there that require the level of expose to struct clk present in this patchset? OMAP does, for now, but if that changes then I need to know if others require this as well.

Regards, Mike

---

arch/arm/mach-omap2/clock44xx_data.c |    4 +++-  arch/arm/mach-omap2/io.c             |    1 -  arch/arm/mach-omap2/timer.c          |    3 +++  3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-omap2/clock44xx_data.c b/arch/arm/mach-omap2/clock44xx_data.c index 7f833a7..5aa8dd2 100644 --- a/arch/arm/mach-omap2/clock44xx_data.c +++ b/arch/arm/mach-omap2/clock44xx_data.c @@ -6032,7 +6032,9 @@ int __init omap4xxx_clk_init(void)                }  # else                clkdev_add(c);

• __clk_init(NULL, c->clk);

• clk_register(NULL, c->clk->name, c->clk->ops, c->clk->hw,
• c->clk->parent_names, c->clk->num_parents, c->clk->flags);

#endif        }

diff --git a/arch/arm/mach-omap2/io.c b/arch/arm/mach-omap2/io.c index eb50c29..8db4380 100644 --- a/arch/arm/mach-omap2/io.c +++ b/arch/arm/mach-omap2/io.c @@ -476,7 +476,6 @@ void __init omap4430_init_early(void)        omap44xx_clockdomains_init();        omap44xx_hwmod_init();        omap_hwmod_init_postsetup();

• omap4xxx_clk_init();

}  #endif

diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c index 5c9acea..2cca796 100644 --- a/arch/arm/mach-omap2/timer.c +++ b/arch/arm/mach-omap2/timer.c @@ -323,9 +323,12 @@ OMAP_SYS_TIMER_INIT(3_secure, OMAP3_SECURE_TIMER, OMAP3_CLKEV_SOURCE,  OMAP_SYS_TIMER(3_secure)  #endif

+int __init omap4xxx_clk_init(void);

#ifdef CONFIG_ARCH_OMAP4  static void __init omap4_timer_init(void)  {

• omap4xxx_clk_init();

#ifdef CONFIG_LOCAL_TIMERS        twd_base = ioremap(OMAP44XX_LOCAL_TWD_BASE, SZ_256);        BUG_ON(!twd_base); -- 1.7.9.1

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Hi Mike,

On Sat, Mar 03, 2012 at 12:29:00AM -0800, Mike Turquette wrote:

[snip]

+static void __clk_disable(struct clk *clk) +{

• if (!clk)

• return;
  

• if (WARN_ON(clk->enable_count == 0))

• return;
  

• if (--clk->enable_count > 0)

• return;
  

• if (clk->ops->disable)

• clk->ops->disable(clk->hw);
  

• if (clk->parent)

• __clk_disable(clk->parent);
  

if __clk_xxx handle NULL clk, we might not need to check parent here? There're also many places that checks parent below.

+}

+/**

• • clk_disable - gate a clock
• • @clk: the clk being gated
• • clk_disable must not sleep, which differentiates it from clk_unprepare. In
• • a simple case, clk_disable can be used instead of clk_unprepare to gate a
• • clk if the operation is fast and will never sleep. One example is a
• • SoC-internal clk which is controlled via simple register writes. In the
• • complex case a clk gate operation may require a fast and a slow part. It is
• • this reason that clk_unprepare and clk_disable are not mutually exclusive.
• • In fact clk_disable must be called before clk_unprepare.
• */

+void clk_disable(struct clk *clk) +{

• unsigned long flags;
• spin_lock_irqsave(&enable_lock, flags);
• __clk_disable(clk);
• spin_unlock_irqrestore(&enable_lock, flags);

+} +EXPORT_SYMBOL_GPL(clk_disable);

+static int __clk_enable(struct clk *clk) +{

• int ret = 0;
• if (!clk)

• return 0;
  

• if (WARN_ON(clk->prepare_count == 0))

• return -ESHUTDOWN;
  

• if (clk->enable_count == 0) {

• if (clk->parent)
  

• 	ret = __clk_enable(clk->parent);
  

ditto

• if (ret)
  

• 	return ret;
  

• if (clk->ops->enable) {
  

• 	ret = clk->ops->enable(clk->hw);
  

• 	if (ret) {
  

• 		__clk_disable(clk->parent);
  

it's good case that don't check parent is NULL.

• 		return ret;
  

• 	}
  

• }
  

• }
• clk->enable_count++;
• return 0;

+}

+/**

• • clk_enable - ungate a clock
• • @clk: the clk being ungated
• • clk_enable must not sleep, which differentiates it from clk_prepare. In a
• • simple case, clk_enable can be used instead of clk_prepare to ungate a clk
• • if the operation will never sleep. One example is a SoC-internal clk which
• • is controlled via simple register writes. In the complex case a clk ungate
• • operation may require a fast and a slow part. It is this reason that
• • clk_enable and clk_prepare are not mutually exclusive. In fact clk_prepare
• • must be called before clk_enable. Returns 0 on success, -EERROR
• • otherwise.
• */

+int clk_enable(struct clk *clk) +{

• unsigned long flags;
• int ret;
• spin_lock_irqsave(&enable_lock, flags);
• ret = __clk_enable(clk);
• spin_unlock_irqrestore(&enable_lock, flags);
• return ret;

+} +EXPORT_SYMBOL_GPL(clk_enable);

+/**

• • clk_get_rate - return the rate of clk
• • @clk: the clk whose rate is being returned
• • Simply returns the cached rate of the clk. Does not query the hardware. If
• • clk is NULL then returns -EINVAL.
• */

+unsigned long clk_get_rate(struct clk *clk) +{

• unsigned long rate;
• mutex_lock(&prepare_lock);
• rate = __clk_get_rate(clk);
• mutex_unlock(&prepare_lock);
• return rate;

+} +EXPORT_SYMBOL_GPL(clk_get_rate);

+/**

• • __clk_round_rate - round the given rate for a clk
• • @clk: round the rate of this clock
• • Caller must hold prepare_lock. Useful for clk_ops such as .set_rate
• */

+unsigned long __clk_round_rate(struct clk *clk, unsigned long rate) +{

• if (!clk && !clk->ops->round_rate)

be || ?

• return -EINVAL;
  

• return clk->ops->round_rate(clk->hw, rate, NULL);

+}

+/**

• • clk_round_rate - round the given rate for a clk
• • @clk: the clk for which we are rounding a rate
• • @rate: the rate which is to be rounded
• • Takes in a rate as input and rounds it to a rate that the clk can actually
• • use which is then returned. If clk doesn't support round_rate operation
• • then the rate passed in is returned.
• */

+long clk_round_rate(struct clk *clk, unsigned long rate) +{

• unsigned long ret = rate;
• mutex_lock(&prepare_lock);
• if (clk && clk->ops->round_rate)

• ret = __clk_round_rate(clk, rate);
  

• mutex_unlock(&prepare_lock);
• return ret;

If clk is NULL, clk_round_rate and __clk_round_rate return different values. Do you mean it?

+} +EXPORT_SYMBOL_GPL(clk_round_rate);

+/**

• • __clk_notify - call clk notifier chain
• • @clk: struct clk * that is changing rate
• • @msg: clk notifier type (see include/linux/clk.h)
• • @old_rate: old clk rate
• • @new_rate: new clk rate
• • Triggers a notifier call chain on the clk rate-change notification
• • for 'clk'. Passes a pointer to the struct clk and the previous
• • and current rates to the notifier callback. Intended to be called by
• • internal clock code only. Returns NOTIFY_DONE from the last driver
• • called if all went well, or NOTIFY_STOP or NOTIFY_BAD immediately if
• • a driver returns that.
• */

+static int __clk_notify(struct clk *clk, unsigned long msg,

• unsigned long old_rate, unsigned long new_rate)
  

+{

• struct clk_notifier *cn;
• struct clk_notifier_data cnd;
• int ret = NOTIFY_DONE;
• cnd.clk = clk;
• cnd.old_rate = old_rate;
• cnd.new_rate = new_rate;
• list_for_each_entry(cn, &clk_notifier_list, node) {

• if (cn->clk == clk) {
  

• 	ret = srcu_notifier_call_chain(&cn->notifier_head, msg,
  

• 			&cnd);
  

• 	break;
  

• }
  

• }
• return ret;

+}

+/**

• • __clk_recalc_rates
• • @clk: first clk in the subtree
• • @msg: notification type (see include/linux/clk.h)
• • Walks the subtree of clks starting with clk and recalculates rates as it
• • goes. Note that if a clk does not implement the recalc_rate operation then
• • propagation of that subtree stops and all of that clks children will not
• • have their rates updated.
• • clk_recalc_rates also propagates the POST_RATE_CHANGE notification,
• • if necessary.
• • Caller must hold prepare_lock.
• */

+static void __clk_recalc_rates(struct clk *clk, unsigned long msg) +{

• unsigned long old_rate;
• unsigned long parent_rate = 0;
• struct hlist_node *tmp;
• struct clk *child;
• old_rate = clk->rate;
• if (clk->parent)

• parent_rate = clk->parent->rate;
  

• if (clk->ops->recalc_rate)

• clk->rate = clk->ops->recalc_rate(clk->hw, parent_rate);
  

• else

• clk->rate = parent_rate;
  

• /*

• * ignore NOTIFY_STOP and NOTIFY_BAD return values for POST_RATE_CHANGE
  

• * & ABORT_RATE_CHANGE notifiers
  

• */
  

• if (clk->notifier_count && msg)

• __clk_notify(clk, msg, old_rate, clk->rate);
  

• hlist_for_each_entry(child, tmp, &clk->children, child_node)

• __clk_recalc_rates(child, msg);
  

+}

+/**

• • __clk_speculate_rates
• • @clk: first clk in the subtree
• • @parent_rate: the "future" rate of clk's parent
• • Walks the subtree of clks starting with clk, speculating rates as it
• • goes and firing off PRE_RATE_CHANGE notifications as necessary.
• • Unlike clk_recalc_rates, clk_speculate_rates exists only for sending
• • pre-rate change notifications and returns early if no clks in the
• • subtree have subscribed to the notifications.
• • Caller must hold prepare_lock.
• */

+static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate) +{

• struct hlist_node *tmp;
• struct clk *child;
• unsigned long new_rate;
• int ret = NOTIFY_DONE;
• if (!clk->ops->recalc_rate)

• goto out;
  

When recalc_rate is NULL, it's possible for it and its children to have notifier too.

• new_rate = clk->ops->recalc_rate(clk->hw, parent_rate);
• /* abort the rate change if a driver returns NOTIFY_BAD */
• if (clk->notifier_count)

• ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
  

• if (ret == NOTIFY_BAD)

• goto out;
  

• hlist_for_each_entry(child, tmp, &clk->children, child_node) {

• ret = __clk_speculate_rates(child, new_rate);
  

• if (ret == NOTIFY_BAD)
  

• 	break;
  

• }

Tell the notifier that already receive PRE_RATE_CHANGE abort?

+out:

• return ret;

+}

+/**

• • DOC: Using the CLK_SET_RATE_PARENT flag
• • __clk_set_rate changes the child's rate before the parent's to more
• • easily handle failure conditions.
• • This means clk might run out of spec for a short time if its rate is
• • increased before the parent's rate is updated.
• • To prevent this consider setting the CLK_SET_RATE_GATE flag on any
• • clk where you also set the CLK_SET_RATE_PARENT flag
• • PRE_RATE_CHANGE notifications are supposed to stack as a rate change
• • request propagates up the clk tree. This reflects the different
• • rates that a downstream clk might experience if left enabled while
• • upstream parents change their rates.
• */

+static struct clk *__clk_set_rate(struct clk *clk, unsigned long rate) +{

• struct clk *fail_clk = NULL;
• int ret = NOTIFY_DONE;
• unsigned long old_rate = clk->rate;
• unsigned long new_rate;
• unsigned long parent_old_rate;
• unsigned long parent_new_rate = 0;
• struct clk *child;
• struct hlist_node *tmp;
• /* bail early if we can't change rate while clk is enabled */
• if ((clk->flags & CLK_SET_RATE_GATE) && clk->enable_count)

• return clk;
  

• /* find the new rate and see if parent rate should change too */
• WARN_ON(!clk->ops->round_rate);
• new_rate = clk->ops->round_rate(clk->hw, rate, &parent_new_rate);
• /* NOTE: pre-rate change notifications will stack */
• if (clk->notifier_count)

• ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
  

if ((clk->flags & CLK_SET_RATE_PARENT) && parent_new_rate) dowstream notify from parent clk?

• if (ret == NOTIFY_BAD)

• return clk;
  

• /* speculate rate changes down the tree */
• hlist_for_each_entry(child, tmp, &clk->children, child_node) {

• ret = __clk_speculate_rates(child, new_rate);
  

• if (ret == NOTIFY_BAD)
  

roll back?

• 	return clk;
  

• }
• /* change the rate of this clk */
• if (clk->ops->set_rate)

If set_rate is NULL, it can fail at the beginning of this function.

• ret = clk->ops->set_rate(clk->hw, new_rate);
  

• if (ret == NOTIFY_BAD)

you mean to check set_rate fail? Notify ABORT_RATE_CHANGE?

• return clk;
  

• /*

• * change the rate of the parent clk if necessary
  

• *
  

• * hitting the nested 'if' path implies we have hit a .set_rate
  

• * failure somewhere upstream while propagating __clk_set_rate
  

• * up the clk tree.  roll back the clk rates one by one and
  

• * return the pointer to the clk that failed.  clk_set_rate will
  

• * use the pointer to propagate a rate-change abort notifier
  

• * from the "highest" point.
  

• */
  

• if ((clk->flags & CLK_SET_RATE_PARENT) && parent_new_rate) {

• parent_old_rate = clk->parent->rate;
  

• fail_clk = __clk_set_rate(clk->parent, parent_new_rate);
  

• /* roll back changes if parent rate change failed */
  

• if (fail_clk) {
  

• 	pr_warn("%s: failed to set parent %s rate to %lu\n",
  

• 			__func__, fail_clk->name,
  

• 			parent_new_rate);
  

• 	/*
  

• 	 * Send PRE_RATE_CHANGE notifiers down the tree
  

• 	 * again, since we're rolling back the rate
  

• 	 * changes due to the abort.
  

• 	 *
  

• 	 * Ignore any NOTIFY_BAD's since this *is* the
  

• 	 * exception handler.
  

• 	 *
  

• 	 * NOTE: pre-rate change notifications will stack
  

• 	 */
  

• 	__clk_speculate_rates(clk, clk->parent->rate);
  

IMHO, driver can not be happy to receive multiple PRE_RATE_CHANGE. Notify ABORT_RATE_CHANGE?

• 	clk->ops->set_rate(clk->hw, old_rate);
  

• }
  

• return fail_clk;
  

• }
• /*

• * set clk's rate & recalculate the rates of clk's children
  

• *
  

• * hitting this path implies we have successfully finished
  

• * propagating recursive calls to __clk_set_rate up the clk tree
  

• * (if necessary) and it is safe to propagate __clk_recalc_rates
  

• * and post-rate change notifiers down the clk tree from this
  

• * point.
  

• */
  

• __clk_recalc_rates(clk, POST_RATE_CHANGE);
• return NULL;

+}

+/**

• • clk_set_rate - specify a new rate for clk
• • @clk: the clk whose rate is being changed
• • @rate: the new rate for clk
• • In the simplest case clk_set_rate will only change the rate of clk.
• • If clk has the CLK_SET_RATE_GATE flag set and it is enabled this call
• • will fail; only when the clk is disabled will it be able to change
• • its rate.
• • Setting the CLK_SET_RATE_PARENT flag allows clk_set_rate to
• • recursively propagate up to clk's parent; whether or not this happens
• • depends on the outcome of clk's .round_rate implementation. If
• • *parent_rate is 0 after calling .round_rate then upstream parent
• • propagation is ignored. If *parent_rate comes back with a new rate
• • for clk's parent then we propagate up to clk's parent and set it's
• • rate. Upward propagation will continue until either a clk does not
• • support the CLK_SET_RATE_PARENT flag or .round_rate stops requesting
• • changes to clk's parent_rate. If there is a failure during upstream
• • propagation then clk_set_rate will unwind and restore each clk's rate
• • that had been successfully changed. Afterwards a rate change abort
• • notification will be propagated downstream, starting from the clk
• • that failed.
• • At the end of all of the rate setting, clk_set_rate internally calls
• • __clk_recalc_rates and propagates the rate changes downstream,
• • starting from the highest clk whose rate was changed. This has the
• • added benefit of propagating post-rate change notifiers.
• • Note that while post-rate change and rate change abort notifications
• • are guaranteed to be sent to a clk only once per call to
• • clk_set_rate, pre-change notifications will be sent for every clk
• • whose rate is changed. Stacking pre-change notifications is noisy
• • for the drivers subscribed to them, but this allows drivers to react
• • to intermediate clk rate changes up until the point where the final
• • rate is achieved at the end of upstream propagation.
• • Returns 0 on success, -EERROR otherwise.
• */

+int clk_set_rate(struct clk *clk, unsigned long rate) +{

• struct clk *fail_clk;
• int ret = 0;
• /* prevent racing with updates to the clock topology */
• mutex_lock(&prepare_lock);
• /* bail early if nothing to do */
• if (rate == clk->rate)

• goto out;
  

• fail_clk = __clk_set_rate(clk, rate);
• if (fail_clk) {

• pr_warn("%s: failed to set %s rate\n", __func__,
  

• 		fail_clk->name);
  

• __clk_recalc_rates(clk, ABORT_RATE_CHANGE);
  

It might need to begin from parent clk. move it to __clk_set_rate?

• ret = -EIO;
  

• }

+out:

• mutex_unlock(&prepare_lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(clk_set_rate);

+/**

• • clk_get_parent - return the parent of a clk
• • @clk: the clk whose parent gets returned
• • Simply returns clk->parent. Returns NULL if clk is NULL.
• */

+struct clk *clk_get_parent(struct clk *clk) +{

• struct clk *parent;
• mutex_lock(&prepare_lock);
• parent = __clk_get_parent(clk);
• mutex_unlock(&prepare_lock);
• return parent;

+} +EXPORT_SYMBOL_GPL(clk_get_parent);

+/*

• • .get_parent is mandatory for clocks with multiple possible parents. It is
• • optional for single-parent clocks. Always call .get_parent if it is
• • available and WARN if it is missing for multi-parent clocks.
• • For single-parent clocks without .get_parent, first check to see if the
• • .parents array exists, and if so use it to avoid an expensive tree
• • traversal. If .parents does not exist then walk the tree with __clk_lookup.
• */

+static struct clk *__clk_init_parent(struct clk *clk) +{

• struct clk *ret = NULL;
• u8 index;
• /* handle the trivial cases */
• if (!clk->num_parents)

• goto out;
  

• if (clk->num_parents == 1) {

• if (IS_ERR_OR_NULL(clk->parent))
  

• 	ret = clk->parent = __clk_lookup(clk->parent_names[0]);
  

• ret = clk->parent;
  

• goto out;
  

• }
• if (!clk->ops->get_parent) {

• WARN(!clk->ops->get_parent,
  

• 	"%s: multi-parent clocks must implement .get_parent\n",
  

• 	__func__);
  

• goto out;
  

• };
• /*

• * Do our best to cache parent clocks in clk->parents.  This prevents
  

• * unnecessary and expensive calls to __clk_lookup.  We don't set
  

• * clk->parent here; that is done by the calling function
  

• */
  

• index = clk->ops->get_parent(clk->hw);
• if (!clk->parents)

• clk->parents =
  

• 	kmalloc((sizeof(struct clk*) * clk->num_parents),
  

• 			GFP_KERNEL);
  

• if (!clk->parents)

• ret = __clk_lookup(clk->parent_names[index]);
  

• else if (!clk->parents[index])

• ret = clk->parents[index] =
  

• 	__clk_lookup(clk->parent_names[index]);
  

• else

• ret = clk->parents[index];
  

+out:

• return ret;

+}

+void __clk_reparent(struct clk *clk, struct clk *new_parent) +{ +#ifdef CONFIG_COMMON_CLK_DEBUG

• struct dentry *d;
• struct dentry *new_parent_d;

+#endif

• if (!clk || !new_parent)

• return;
  

• hlist_del(&clk->child_node);
• if (new_parent)

• hlist_add_head(&clk->child_node, &new_parent->children);
  

• else

• hlist_add_head(&clk->child_node, &clk_orphan_list);
  

+#ifdef CONFIG_COMMON_CLK_DEBUG

• if (!inited)

• goto out;
  

• if (new_parent)

• new_parent_d = new_parent->dentry;
  

• else

• new_parent_d = orphandir;
  

• d = debugfs_rename(clk->dentry->d_parent, clk->dentry,

• 	new_parent_d, clk->name);
  

• if (d)

• clk->dentry = d;
  

• else

• pr_debug("%s: failed to rename debugfs entry for %s\n",
  

• 		__func__, clk->name);
  

+out: +#endif

• clk->parent = new_parent;
• __clk_recalc_rates(clk, POST_RATE_CHANGE);

+}

+static int __clk_set_parent(struct clk *clk, struct clk *parent) +{

• struct clk *old_parent;
• unsigned long flags;
• int ret = -EINVAL;
• u8 i;
• old_parent = clk->parent;
• /* find index of new parent clock using cached parent ptrs */
• for (i = 0; i < clk->num_parents; i++)

• if (clk->parents[i] == parent)
  

• 	break;
  

• /*

• * find index of new parent clock using string name comparison
  

• * also try to cache the parent to avoid future calls to __clk_lookup
  

• */
  

• if (i == clk->num_parents)

• for (i = 0; i < clk->num_parents; i++)
  

• 	if (!strcmp(clk->parent_names[i], parent->name)) {
  

• 		clk->parents[i] = __clk_lookup(parent->name);
  

• 		break;
  

• 	}
  

• if (i == clk->num_parents) {

• pr_debug("%s: clock %s is not a possible parent of clock %s\n",
  

• 		__func__, parent->name, clk->name);
  

• goto out;
  

• }
• /* migrate prepare and enable */
• if (clk->prepare_count)

• __clk_prepare(parent);
  

• /* FIXME replace with clk_is_enabled(clk) someday */
• spin_lock_irqsave(&enable_lock, flags);
• if (clk->enable_count)

• __clk_enable(parent);
  

• spin_unlock_irqrestore(&enable_lock, flags);
• /* change clock input source */
• ret = clk->ops->set_parent(clk->hw, i);
• /* clean up old prepare and enable */
• spin_lock_irqsave(&enable_lock, flags);
• if (clk->enable_count)

• __clk_disable(old_parent);
  

• spin_unlock_irqrestore(&enable_lock, flags);
• if (clk->prepare_count)

• __clk_unprepare(old_parent);
  

+out:

• return ret;

+}

+/**

• • clk_set_parent - switch the parent of a mux clk
• • @clk: the mux clk whose input we are switching
• • @parent: the new input to clk
• • Re-parent clk to use parent as it's new input source. If clk has the
• • CLK_SET_PARENT_GATE flag set then clk must be gated for this
• • operation to succeed. After successfully changing clk's parent
• • clk_set_parent will update the clk topology, sysfs topology and
• • propagate rate recalculation via __clk_recalc_rates. Returns 0 on
• • success, -EERROR otherwise.
• */

+int clk_set_parent(struct clk *clk, struct clk *parent) +{

• int ret = 0;
• if (!clk || !clk->ops)

• return -EINVAL;
  

• if (!clk->ops->set_parent)

• return -ENOSYS;
  

• /* prevent racing with updates to the clock topology */
• mutex_lock(&prepare_lock);
• if (clk->parent == parent)

• goto out;
  

• /* propagate PRE_RATE_CHANGE notifications */
• if (clk->notifier_count)

• ret = __clk_speculate_rates(clk, parent->rate);
  

• /* abort if a driver objects */
• if (ret == NOTIFY_STOP)

• goto out;
  

• /* only re-parent if the clock is not in use */
• if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count)

• ret = -EBUSY;
  

• else

• ret = __clk_set_parent(clk, parent);
  

• /* propagate ABORT_RATE_CHANGE if .set_parent failed */
• if (ret) {

• __clk_recalc_rates(clk, ABORT_RATE_CHANGE);
  

• goto out;
  

• }
• /* propagate rate recalculation downstream */
• __clk_reparent(clk, parent);

+out:

• mutex_unlock(&prepare_lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(clk_set_parent);

+/**

• • __clk_init - initialize the data structures in a struct clk
• • @dev: device initializing this clk, placeholder for now
• • @clk: clk being initialized
• • Initializes the lists in struct clk, queries the hardware for the
• • parent and rate and sets them both.
• • Any struct clk passed into __clk_init must have the following members
• • populated:
• • .name
• • .ops
• • .hw
• • .parent_names
• • .num_parents
• • .flags
• • Essentially, everything that would normally be passed into clk_register is
• • assumed to be initialized already in __clk_init. The other members may be
• • populated, but are optional.
• • __clk_init is only exposed via clk-private.h and is intended for use with
• • very large numbers of clocks that need to be statically initialized. It is
• • a layering violation to include clk-private.h from any code which implements
• • a clock's .ops; as such any statically initialized clock data MUST be in a
• • separate C file from the logic that implements it's operations.
• */

+void __clk_init(struct device *dev, struct clk *clk) +{

• int i;
• struct clk *orphan;
• struct hlist_node *tmp;
• if (!clk)

• return;
  

• mutex_lock(&prepare_lock);
• /* check to see if a clock with this name is already registered */
• if (__clk_lookup(clk->name))

• goto out;
  

• /*

• * Allocate an array of struct clk *'s to avoid unnecessary string
  

• * look-ups of clk's possible parents.  This can fail for clocks passed
  

• * in to clk_init during early boot; thus any access to clk->parents[]
  

• * must always check for a NULL pointer and try to populate it if
  

• * necessary.
  

• *
  

• * If clk->parents is not NULL we skip this entire block.  This allows
  

• * for clock drivers to statically initialize clk->parents.
  

• */
  

• if (clk->num_parents && !clk->parents) {

• clk->parents = kmalloc((sizeof(struct clk*) * clk->num_parents),
  

• 		GFP_KERNEL);
  

• /*
  

•  * __clk_lookup returns NULL for parents that have not been
  

•  * clk_init'd; thus any access to clk->parents[] must check
  

•  * for a NULL pointer.  We can always perform lazy lookups for
  

•  * missing parents later on.
  

•  */
  

• if (clk->parents)
  

• 	for (i = 0; i < clk->num_parents; i++)
  

• 		clk->parents[i] =
  

• 			__clk_lookup(clk->parent_names[i]);
  

• }
• clk->parent = __clk_init_parent(clk);
• /*

• * Populate clk->parent if parent has already been __clk_init'd.  If
  

• * parent has not yet been __clk_init'd then place clk in the orphan
  

• * list.  If clk has set the CLK_IS_ROOT flag then place it in the root
  

• * clk list.
  

• *
  

• * Every time a new clk is clk_init'd then we walk the list of orphan
  

• * clocks and re-parent any that are children of the clock currently
  

• * being clk_init'd.
  

• */
  

• if (clk->parent)

• hlist_add_head(&clk->child_node,
  

• 		&clk->parent->children);
  

• else if (clk->flags & CLK_IS_ROOT)

• hlist_add_head(&clk->child_node, &clk_root_list);
  

• else

• hlist_add_head(&clk->child_node, &clk_orphan_list);
  

• /*

• * Set clk's rate.  The preferred method is to use .recalc_rate.  For
  

• * simple clocks and lazy developers the default fallback is to use the
  

• * parent's rate.  If a clock doesn't have a parent (or is orphaned)
  

• * then rate is set to zero.
  

• */
  

• if (clk->ops->recalc_rate)

• clk->rate = clk->ops->recalc_rate(clk->hw,
  

• 		__clk_get_rate(clk->parent));
  

• else if (clk->parent)

• clk->rate = clk->parent->rate;
  

• else

• clk->rate = 0;
  

• /*

• * walk the list of orphan clocks and reparent any that are children of
  

• * this clock
  

• */
  

• hlist_for_each_entry(orphan, tmp, &clk_orphan_list, child_node)

• __clk_reparent(orphan, __clk_init_parent(orphan));
  

check whether orphan->parent is the value of __clk_init_parent(orphan) before reparent?

• /*

• * optional platform-specific magic
  

• *
  

• * The .init callback is not used by any of the basic clock types, but
  

• * exists for weird hardware that must perform initialization magic.
  

• * Please consider other ways of solving initialization problems before
  

• * using this callback, as it's use is discouraged.
  

• */
  

• if (clk->ops->init)

• clk->ops->init(clk->hw);
  

• clk_debug_register(clk);

+out:

• mutex_unlock(&prepare_lock);
• return;

+}

+/**

• • clk_register - allocate a new clock, register it and return an opaque cookie
• • @dev: device that is registering this clock
• • @name: clock name
• • @ops: operations this clock supports
• • @hw: link to hardware-specific clock data
• • @parent_names: array of string names for all possible parents
• • @num_parents: number of possible parents
• • @flags: framework-level hints and quirks
• • clk_register is the primary interface for populating the clock tree with new
• • clock nodes. It returns a pointer to the newly allocated struct clk which
• • cannot be dereferenced by driver code but may be used in conjuction with the
• • rest of the clock API.
• */

+struct clk *clk_register(struct device *dev, const char *name,

• const struct clk_ops *ops, struct clk_hw *hw,
  

• char **parent_names, u8 num_parents, unsigned long flags)
  

+{

• struct clk *clk;
• clk = kzalloc(sizeof(*clk), GFP_KERNEL);
• if (!clk)

• return NULL;
  

• clk->name = name;
• clk->ops = ops;
• clk->hw = hw;
• clk->flags = flags;
• clk->parent_names = parent_names;
• clk->num_parents = num_parents;
• hw->clk = clk;
• __clk_init(dev, clk);
• return clk;

+} +EXPORT_SYMBOL_GPL(clk_register);

+/*** clk rate change notifiers ***/

+/**

• • clk_notifier_register - add a clk rate change notifier
• • @clk: struct clk * to watch
• • @nb: struct notifier_block * with callback info
• • Request notification when clk's rate changes. This uses an SRCU
• • notifier because we want it to block and notifier unregistrations are
• • uncommon. The callbacks associated with the notifier must not
• • re-enter into the clk framework by calling any top-level clk APIs;
• • this will cause a nested prepare_lock mutex.
• • Pre-change notifier callbacks will be passed the current, pre-change
• • rate of the clk via struct clk_notifier_data.old_rate. The new,
• • post-change rate of the clk is passed via struct
• • clk_notifier.new_rate.

clk_notifier_data ?

• • Post-change notifiers will pass the now-current, post-change rate of
• • the clk in both struct clk_notifier_data.old_rate and struct
• • clk_notifier_data.new_rate.
• • Abort-change notifiers are effectively the opposite of pre-change
• • notifiers: the original pre-change clk rate is passed in via struct
• • clk_notifier_data.new_rate and the failed post-change rate is passed
• • in via struct clk_notifier_data.old_rate.
• • clk_notifier_register() must be called from non-atomic context.
• • Returns -EINVAL if called with null arguments, -ENOMEM upon
• • allocation failure; otherwise, passes along the return value of
• • srcu_notifier_chain_register().
• */

+int clk_notifier_register(struct clk *clk, struct notifier_block *nb) +{

• struct clk_notifier *cn;
• int ret = -ENOMEM;
• if (!clk || !nb)

• return -EINVAL;
  

• mutex_lock(&prepare_lock);
• /* search the list of notifiers for this clk */
• list_for_each_entry(cn, &clk_notifier_list, node)

• if (cn->clk == clk)
  

• 	break;
  

• /* if clk wasn't in the notifier list, allocate new clk_notifier */
• if (cn->clk != clk) {

• cn = kzalloc(sizeof(struct clk_notifier), GFP_KERNEL);
  

• if (!cn)
  

• 	goto out;
  

• cn->clk = clk;
  

• srcu_init_notifier_head(&cn->notifier_head);
  

• list_add(&cn->node, &clk_notifier_list);
  

• }

why not embedd notifier_head to struct clk?

• ret = srcu_notifier_chain_register(&cn->notifier_head, nb);
• clk->notifier_count++;

+out:

• mutex_unlock(&prepare_lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(clk_notifier_register);

+/**

• • clk_notifier_unregister - remove a clk rate change notifier
• • @clk: struct clk *
• • @nb: struct notifier_block * with callback info
• • Request no further notification for changes to 'clk' and frees memory
• • allocated in clk_notifier_register.
• • Returns -EINVAL if called with null arguments; otherwise, passes
• • along the return value of srcu_notifier_chain_unregister().
• */

+int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb) +{

• struct clk_notifier *cn = NULL;
• int ret = -EINVAL;
• if (!clk || !nb)

• return -EINVAL;
  

• mutex_lock(&prepare_lock);
• list_for_each_entry(cn, &clk_notifier_list, node)

• if (cn->clk == clk)
  

• 	break;
  

• if (cn->clk == clk) {

• ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
  

• clk->notifier_count--;
  

• /* XXX the notifier code should handle this better */
  

• if (!cn->notifier_head.head) {
  

• 	srcu_cleanup_notifier_head(&cn->notifier_head);
  

• 	kfree(cn);
  

• }
  

• } else {

• ret = -ENOENT;
  

• }
• mutex_unlock(&prepare_lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(clk_notifier_unregister); diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h new file mode 100644 index 0000000..33bf6a7 --- /dev/null +++ b/include/linux/clk-private.h @@ -0,0 +1,68 @@ +/*

• • linux/include/linux/clk-private.h
• • Copyright (c) 2010-2011 Jeremy Kerr jeremy.kerr@canonical.com
• • Copyright (C) 2011-2012 Linaro Ltd mturquette@linaro.org
• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License version 2 as
• • published by the Free Software Foundation.
• */

+#ifndef __LINUX_CLK_PRIVATE_H +#define __LINUX_CLK_PRIVATE_H

+#include <linux/clk-provider.h> +#include <linux/list.h>

+/*

• • WARNING: Do not include clk-private.h from any file that implements struct
• • clk_ops. Doing so is a layering violation!
• • This header exists only to allow for statically initialized clock data. Any
• • static clock data must be defined in a separate file from the logic that
• • implements the clock operations for that same data.
• */

+#ifdef CONFIG_COMMON_CLK

+struct clk {

• const char *name;
• const struct clk_ops *ops;
• struct clk_hw *hw;
• struct clk *parent;
• char **parent_names;
• struct clk **parents;
• u8 num_parents;
• unsigned long rate;
• unsigned long flags;
• unsigned int enable_count;
• unsigned int prepare_count;
• struct hlist_head children;
• struct hlist_node child_node;
• unsigned int notifier_count;

+#ifdef CONFIG_COMMON_CLK_DEBUG

• struct dentry *dentry;

+#endif +};

+/**

• • __clk_init - initialize the data structures in a struct clk
• • @dev: device initializing this clk, placeholder for now
• • @clk: clk being initialized
• • Initializes the lists in struct clk, queries the hardware for the
• • parent and rate and sets them both.

Add: clocks that call __clk_init don't need to call clk_register.

• • Any struct clk passed into __clk_init must have the following members
• • populated:
• • .name
• • .ops
• • .hw
• • .parent_names
• • .num_parents
• • .flags
• */

+void __clk_init(struct device *dev, struct clk *clk);

+#endif /* CONFIG_COMMON_CLK */ +#endif /* CLK_PRIVATE_H */ diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h new file mode 100644 index 0000000..c9ed582 --- /dev/null +++ b/include/linux/clk-provider.h @@ -0,0 +1,169 @@ +/*

• • linux/include/linux/clk-provider.h
• • Copyright (c) 2010-2011 Jeremy Kerr jeremy.kerr@canonical.com
• • Copyright (C) 2011-2012 Linaro Ltd mturquette@linaro.org
• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License version 2 as
• • published by the Free Software Foundation.
• */

+#ifndef __LINUX_CLK_PROVIDER_H +#define __LINUX_CLK_PROVIDER_H

+#include <linux/clk.h>

+#ifdef CONFIG_COMMON_CLK

+/**

• • struct clk_hw - handle for traversing from a struct clk to its corresponding
• • hardware-specific structure. struct clk_hw should be declared within struct
• • clk_foo and then referenced by the struct clk instance that uses struct
• • clk_foo's clk_ops
• • clk: pointer to the struct clk instance that points back to this struct
• • clk_hw instance
• */

+struct clk_hw {

• struct clk *clk;

+};

+/*

• • flags used across common struct clk. these flags should only affect the
• • top-level framework. custom flags for dealing with hardware specifics
• • belong in struct clk_foo
• */

+#define CLK_SET_RATE_GATE BIT(0) /* must be gated across rate change */ +#define CLK_SET_PARENT_GATE BIT(1) /* must be gated across re-parent */ +#define CLK_SET_RATE_PARENT BIT(2) /* propagate rate change up one level */ +#define CLK_IGNORE_UNUSED BIT(3) /* do not gate even if unused */

I can not find anywhere check it.

+#define CLK_IS_ROOT BIT(4) /* root clk, has no parent */

+/**

• • struct clk_ops - Callback operations for hardware clocks; these are to
• • be provided by the clock implementation, and will be called by drivers
• • through the clk_* api.
• • @prepare: Prepare the clock for enabling. This must not return until

• • the clock is fully prepared, and it's safe to call clk_enable.
    

• • This callback is intended to allow clock implementations to
    

• • do any initialisation that may sleep. Called with
    

• • prepare_lock held.
    

• • @unprepare: Release the clock from its prepared state. This will typically

• • undo any work done in the @prepare callback. Called with
    

• • prepare_lock held.
    

• • @enable: Enable the clock atomically. This must not return until the

• • clock is generating a valid clock signal, usable by consumer
    

• • devices. Called with enable_lock held. This function must not
    

• • sleep.
    

• • @disable: Disable the clock atomically. Called with enable_lock held.

• • This function must not sleep.
    

• • @recalc_rate Recalculate the rate of this clock, by quering hardware. The

• • parent rate is an input parameter.  It is up to the caller to
    

• • insure that the prepare_mutex is held across this call.
    

• • Returns the calculated rate.  Optional, but recommended - if
    

• • this op is not set then clock rate will be initialized to 0.
    

• • @round_rate: Given a target rate as input, returns the closest rate actually

• • supported by the clock.
    

• • @get_parent: Queries the hardware to determine the parent of a clock. The

• • return value is a u8 which specifies the index corresponding to
    

• • the parent clock.  This index can be applied to either the
    

• • .parent_names or .parents arrays.  In short, this function
    

• • translates the parent value read from hardware into an array
    

• • index.  Currently only called when the clock is initialized by
    

• • __clk_init.  This callback is mandatory for clocks with
    

• • multiple parents.  It is optional (and unnecessary) for clocks
    

• • with 0 or 1 parents.
    

• • @set_parent: Change the input source of this clock; for clocks with multiple

• • possible parents specify a new parent by passing in the index
    

• • as a u8 corresponding to the parent in either the .parent_names
    

• • or .parents arrays.  This function in affect translates an
    

• • array index into the value programmed into the hardware.
    

• • Returns 0 on success, -EERROR otherwise.
    

• • @set_rate: Change the rate of this clock. If this callback returns

• • CLK_SET_RATE_PARENT, the rate change will be propagated to the
    

• • parent clock (which may propagate again if the parent clock
    

• • also sets this flag). The requested rate of the parent is
    

• • passed back from the callback in the second 'unsigned long *'
    

• • argument.  Note that it is up to the hardware clock's set_rate
    

• • implementation to insure that clocks do not run out of spec
    

• • when propgating the call to set_rate up to the parent.  One way
    

• • to do this is to gate the clock (via clk_disable and/or
    

• • clk_unprepare) before calling clk_set_rate, then ungating it
    

• • afterward.  If your clock also has the CLK_GATE_SET_RATE flag
    

• • set then this will insure safety.  Returns 0 on success,
    

• • -EERROR otherwise.
    

• • The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
• • implementations to split any work between atomic (enable) and sleepable
• • (prepare) contexts. If enabling a clock requires code that might sleep,
• • this must be done in clk_prepare. Clock enable code that will never be
• • called in a sleepable context may be implement in clk_enable.
• • Typically, drivers will call clk_prepare when a clock may be needed later
• • (eg. when a device is opened), and clk_enable when the clock is actually
• • required (eg. from an interrupt). Note that clk_prepare MUST have been
• • called before clk_enable.
• */

+struct clk_ops {

• int (*prepare)(struct clk_hw *hw);
• void (*unprepare)(struct clk_hw *hw);
• int (*enable)(struct clk_hw *hw);
• void (*disable)(struct clk_hw *hw);
• unsigned long (*recalc_rate)(struct clk_hw *hw,

• 			unsigned long parent_rate);
  

• long (*round_rate)(struct clk_hw *hw, unsigned long,

• 			unsigned long *);
  

• int (*set_parent)(struct clk_hw *hw, u8 index);
• u8 (*get_parent)(struct clk_hw *hw);
• int (*set_rate)(struct clk_hw *hw, unsigned long);
• void (*init)(struct clk_hw *hw);

+};

+/**

• • clk_register - allocate a new clock, register it and return an opaque cookie
• • @dev: device that is registering this clock
• • @name: clock name
• • @ops: operations this clock supports
• • @hw: link to hardware-specific clock data
• • @parent_names: array of string names for all possible parents
• • @num_parents: number of possible parents
• • @flags: framework-level hints and quirks
• • clk_register is the primary interface for populating the clock tree with new
• • clock nodes. It returns a pointer to the newly allocated struct clk which
• • cannot be dereferenced by driver code but may be used in conjuction with the
• • rest of the clock API.
• */

+struct clk *clk_register(struct device *dev, const char *name,

• const struct clk_ops *ops, struct clk_hw *hw,
  

• char **parent_names, u8 num_parents, unsigned long flags);
  

+/* helper functions */ +const char *__clk_get_name(struct clk *clk); +struct clk_hw *__clk_get_hw(struct clk *clk); +u8 __clk_get_num_parents(struct clk *clk); +struct clk *__clk_get_parent(struct clk *clk); +unsigned long __clk_get_rate(struct clk *clk); +unsigned long __clk_get_flags(struct clk *clk); +struct clk *__clk_lookup(const char *name);

+/*

• • FIXME clock api without lock protection
• */

+int __clk_prepare(struct clk *clk); +void __clk_unprepare(struct clk *clk); +void __clk_reparent(struct clk *clk, struct clk *new_parent);

It only notify POST_RATE_CHANGE without PRE_RATE_CHANGE. Mabe we need to move PRE_RATE_CHANGE to __clk_reparent too?

+unsigned long __clk_round_rate(struct clk *clk, unsigned long rate);

why're there no enable/disable functions?

+#endif /* CONFIG_COMMON_CLK */ +#endif /* CLK_PROVIDER_H */ diff --git a/include/linux/clk.h b/include/linux/clk.h index b9d46fa..b025272 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -3,6 +3,7 @@

• Copyright (C) 2004 ARM Limited.
• Written by Deep Blue Solutions Limited.

• • Copyright (C) 2011-2012 Linaro Ltd mturquette@linaro.org
  • This program is free software; you can redistribute it and/or modify
  • it under the terms of the GNU General Public License version 2 as

@@ -12,18 +13,75 @@ #define __LINUX_CLK_H #include <linux/kernel.h> +#include <linux/notifier.h> struct device; -/*

• • The base API.

+struct clk;

+#ifdef CONFIG_COMMON_CLK

+/**

• • DOC: clk notifier callback types
• • PRE_RATE_CHANGE - called immediately before the clk rate is changed,

• • to indicate that the rate change will proceed.  Drivers must
    

• • immediately terminate any operations that will be affected by the
    

• • rate change.  Callbacks may either return NOTIFY_DONE or
    

• • NOTIFY_STOP.
    

• • ABORT_RATE_CHANGE: called if the rate change failed for some reason

• • after PRE_RATE_CHANGE.  In this case, all registered notifiers on
    

• • the clk will be called with ABORT_RATE_CHANGE. Callbacks must
    

• • always return NOTIFY_DONE.
    

• • POST_RATE_CHANGE - called after the clk rate change has successfully

• • completed.  Callbacks must always return NOTIFY_DONE.
    

• */

+#define PRE_RATE_CHANGE BIT(0) +#define POST_RATE_CHANGE BIT(1) +#define ABORT_RATE_CHANGE BIT(2) +/**

• • struct clk_notifier - associate a clk with a notifier
• • @clk: struct clk * to associate the notifier with
• • @notifier_head: a blocking_notifier_head for this clk
• • @node: linked list pointers
• • A list of struct clk_notifier is maintained by the notifier code.
• • An entry is created whenever code registers the first notifier on a
• • particular @clk. Future notifiers on that @clk are added to the
• • @notifier_head.
• */

+struct clk_notifier {

• struct clk *clk;
• struct srcu_notifier_head notifier_head;
• struct list_head node;

+}; -/*

• • struct clk - an machine class defined object / cookie.

+/**

• • struct clk_notifier_data - rate data to pass to the notifier callback
• • @clk: struct clk * being changed
• • @old_rate: previous rate of this clk
• • @new_rate: new rate of this clk
• • For a pre-notifier, old_rate is the clk's rate before this rate
• • change, and new_rate is what the rate will be in the future. For a
• • post-notifier, old_rate and new_rate are both set to the clk's
• • current rate (this was done to optimize the implementation).
  */

-struct clk; +struct clk_notifier_data {

• struct clk *clk;
• unsigned long old_rate;
• unsigned long new_rate;

+};

+int clk_notifier_register(struct clk *clk, struct notifier_block *nb);

+int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb);

+#endif /* !CONFIG_COMMON_CLK */ /**

• clk_get - lookup and obtain a reference to a clock producer.

Thanks Richard

On Sat, Mar 03, 2012 at 12:29:00AM -0800, Mike Turquette wrote:

The common clock framework defines a common struct clk useful across most platforms as well as an implementation of the clk api that drivers can use safely for managing clocks.

The net result is consolidation of many different struct clk definitions and platform-specific clock framework implementations.

This patch introduces the common struct clk, struct clk_ops and an implementation of the well-known clock api in include/clk/clk.h. Platforms may define their own hardware-specific clock structure and their own clock operation callbacks, so long as it wraps an instance of struct clk_hw.

See Documentation/clk.txt for more details.

This patch is based on the work of Jeremy Kerr, which in turn was based on the work of Ben Herrenschmidt.

Signed-off-by: Mike Turquette mturquette@linaro.org Signed-off-by: Mike Turquette mturquette@ti.com Cc: Jeremy Kerr jeremy.kerr@canonical.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Arnd Bergman arnd.bergmann@linaro.org Cc: Paul Walmsley paul@pwsan.com Cc: Shawn Guo shawn.guo@freescale.com Cc: Richard Zhao richard.zhao@linaro.org Cc: Saravana Kannan skannan@codeaurora.org Cc: Magnus Damm magnus.damm@gmail.com Cc: Rob Herring rob.herring@calxeda.com Cc: Mark Brown broonie@opensource.wolfsonmicro.com Cc: Linus Walleij linus.walleij@stericsson.com Cc: Stephen Boyd sboyd@codeaurora.org Cc: Amit Kucheria amit.kucheria@linaro.org Cc: Deepak Saxena dsaxena@linaro.org Cc: Grant Likely grant.likely@secretlab.ca Cc: Andrew Lunn andrew@lunn.ch

---

drivers/clk/Kconfig | 28 + drivers/clk/Makefile | 1 + drivers/clk/clk.c | 1323 ++++++++++++++++++++++++++++++++++++++++++ include/linux/clk-private.h | 68 +++ include/linux/clk-provider.h | 169 ++++++ include/linux/clk.h | 68 ++- 6 files changed, 1652 insertions(+), 5 deletions(-) create mode 100644 drivers/clk/clk.c create mode 100644 include/linux/clk-private.h create mode 100644 include/linux/clk-provider.h

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig index 3912576..18eb8c2 100644 --- a/drivers/clk/Kconfig +++ b/drivers/clk/Kconfig @@ -11,3 +11,31 @@ config HAVE_MACH_CLKDEV config HAVE_CLK_PREPARE bool

+menuconfig COMMON_CLK

• bool "Common Clock Framework"
• select HAVE_CLK_PREPARE
• ---help---

•  The common clock framework is a single definition of struct
  

•  clk, useful across many platforms, as well as an
  

•  implementation of the clock API in include/linux/clk.h.
  

•  Architectures utilizing the common struct clk should select
  

•  this automatically, but it may be necessary to manually select
  

•  this option for loadable modules requiring the common clock
  

•  framework.
  

•  If in doubt, say "N".
  

+if COMMON_CLK

+config COMMON_CLK_DEBUG

• bool "DebugFS representation of clock tree"
• depends on COMMON_CLK
• ---help---

•  Creates a directory hierchy in debugfs for visualizing the clk
  

•  tree structure.  Each directory contains read-only members
  

•  that export information specific to that clk node: clk_rate,
  

•  clk_flags, clk_prepare_count, clk_enable_count &
  

•  clk_notifier_count.
  

+endif diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 07613fa..ff362c4 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -1,2 +1,3 @@ obj-$(CONFIG_CLKDEV_LOOKUP) += clkdev.o +obj-$(CONFIG_COMMON_CLK) += clk.o diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c new file mode 100644 index 0000000..b979d74 --- /dev/null +++ b/drivers/clk/clk.c @@ -0,0 +1,1323 @@ +/*

• • Copyright (C) 2010-2011 Canonical Ltd jeremy.kerr@canonical.com
• • Copyright (C) 2011-2012 Linaro Ltd mturquette@linaro.org
• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License version 2 as
• • published by the Free Software Foundation.
• • Standard functionality for the common clock API. See Documentation/clk.txt
• */

+#include <linux/clk-private.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/spinlock.h> +#include <linux/err.h> +#include <linux/list.h> +#include <linux/slab.h>

+static DEFINE_SPINLOCK(enable_lock); +static DEFINE_MUTEX(prepare_lock);

+static HLIST_HEAD(clk_root_list); +static HLIST_HEAD(clk_orphan_list); +static LIST_HEAD(clk_notifier_list);

+/*** debugfs support ***/

+#ifdef CONFIG_COMMON_CLK_DEBUG +#include <linux/debugfs.h>

+static struct dentry *rootdir; +static struct dentry *orphandir; +static int inited = 0;

+/* caller must hold prepare_lock */ +static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry) +{

• struct dentry *d;
• int ret = -ENOMEM;
• if (!clk || !pdentry) {

• ret = -EINVAL;
  

• goto out;
  

• }
• d = debugfs_create_dir(clk->name, pdentry);
• if (!d)

• goto out;
  

• clk->dentry = d;
• d = debugfs_create_u32("clk_rate", S_IRUGO, clk->dentry,

• 	(u32 *)&clk->rate);
  

• if (!d)

• goto err_out;
  

• d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,

• 	(u32 *)&clk->flags);
  

• if (!d)

• goto err_out;
  

• d = debugfs_create_u32("clk_prepare_count", S_IRUGO, clk->dentry,

• 	(u32 *)&clk->prepare_count);
  

• if (!d)

• goto err_out;
  

• d = debugfs_create_u32("clk_enable_count", S_IRUGO, clk->dentry,

• 	(u32 *)&clk->enable_count);
  

• if (!d)

• goto err_out;
  

• d = debugfs_create_u32("clk_notifier_count", S_IRUGO, clk->dentry,

• 	(u32 *)&clk->notifier_count);
  

• if (!d)

• goto err_out;
  

• ret = 0;
• goto out;

+err_out:

• debugfs_remove(clk->dentry);

+out:

• return ret;

+}

+/* caller must hold prepare_lock */ +static int clk_debug_create_subtree(struct clk *clk, struct dentry *pdentry) +{

• struct clk *child;
• struct hlist_node *tmp;
• int ret = -EINVAL;;
• if (!clk || !pdentry)

• goto out;
  

• ret = clk_debug_create_one(clk, pdentry);
• if (ret)

• goto out;
  

• hlist_for_each_entry(child, tmp, &clk->children, child_node)

• clk_debug_create_subtree(child, clk->dentry);
  

• ret = 0;

+out:

• return ret;

+}

+/**

• • clk_debug_register - add a clk node to the debugfs clk tree
• • @clk: the clk being added to the debugfs clk tree
• • Dynamically adds a clk to the debugfs clk tree if debugfs has been
• • initialized. Otherwise it bails out early since the debugfs clk tree
• • will be created lazily by clk_debug_init as part of a late_initcall.
• • Caller must hold prepare_lock. Only clk_init calls this function (so
• • far) so this is taken care.
• */

+static int clk_debug_register(struct clk *clk) +{

• struct clk *parent;
• struct dentry *pdentry;
• int ret = 0;
• if (!inited)

• goto out;
  

• parent = clk->parent;
• /*

• * Check to see if a clk is a root clk.  Also check that it is
  

• * safe to add this clk to debugfs
  

• */
  

• if (!parent)

• if (clk->flags & CLK_IS_ROOT)
  

• 	pdentry = rootdir;
  

• else
  

• 	pdentry = orphandir;
  

• else

• if (parent->dentry)
  

• 	pdentry = parent->dentry;
  

• else
  

• 	goto out;
  

• ret = clk_debug_create_subtree(clk, pdentry);

+out:

• return ret;

+}

+/**

• • clk_debug_init - lazily create the debugfs clk tree visualization
• • clks are often initialized very early during boot before memory can
• • be dynamically allocated and well before debugfs is setup.
• • clk_debug_init walks the clk tree hierarchy while holding
• • prepare_lock and creates the topology as part of a late_initcall,
• • thus insuring that clks initialized very early will still be
• • represented in the debugfs clk tree. This function should only be
• • called once at boot-time, and all other clks added dynamically will
• • be done so with clk_debug_register.
• */

+static int __init clk_debug_init(void) +{

• struct clk *clk;
• struct hlist_node *tmp;
• rootdir = debugfs_create_dir("clk", NULL);
• if (!rootdir)

• return -ENOMEM;
  

• orphandir = debugfs_create_dir("orphans", rootdir);
• if (!orphandir)

• return -ENOMEM;
  

• mutex_lock(&prepare_lock);
• hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)

• clk_debug_create_subtree(clk, rootdir);
  

• hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)

• clk_debug_create_subtree(clk, orphandir);
  

• inited = 1;
• mutex_unlock(&prepare_lock);
• return 0;

+} +late_initcall(clk_debug_init); +#else +static inline int clk_debug_register(struct clk *clk) { return 0; } +#endif /* CONFIG_COMMON_CLK_DEBUG */

+/*** helper functions ***/

+inline const char *__clk_get_name(struct clk *clk) +{

• return !clk ? NULL : clk->name;

+}

+inline struct clk_hw *__clk_get_hw(struct clk *clk) +{

• return !clk ? NULL : clk->hw;

+}

+inline u8 __clk_get_num_parents(struct clk *clk) +{

• return !clk ? -EINVAL : clk->num_parents;

+}

+inline struct clk *__clk_get_parent(struct clk *clk) +{

• return !clk ? NULL : clk->parent;

+}

+inline unsigned long __clk_get_rate(struct clk *clk) +{

• return !clk ? -EINVAL : clk->rate;

+}

+inline unsigned long __clk_get_flags(struct clk *clk) +{

• return !clk ? -EINVAL : clk->flags;

+}

+static struct clk *__clk_lookup_subtree(const char *name, struct clk *clk) +{

• struct clk *child;
• struct clk *ret;
• struct hlist_node *tmp;
• if (!strcmp(clk->name, name))

• return clk;
  

• hlist_for_each_entry(child, tmp, &clk->children, child_node) {

• ret = __clk_lookup_subtree(name, child);
  

• if (ret)
  

• 	return ret;
  

• }
• return NULL;

+}

+struct clk *__clk_lookup(const char *name) +{

• struct clk *root_clk;
• struct clk *ret;
• struct hlist_node *tmp;

This should have a check for NULL pointers. NULL pointers can happen here if a mux has holes in it. In this case the parent name array would look like this:

{ "parentclk1", "parentclk2", NULL /* reserved */, "parentclk3" }

Without checking for NULL pointers we dereference the NULL pointer here.

+/**

• • __clk_round_rate - round the given rate for a clk
• • @clk: round the rate of this clock
• • Caller must hold prepare_lock. Useful for clk_ops such as .set_rate
• */

+unsigned long __clk_round_rate(struct clk *clk, unsigned long rate) +{

• if (!clk && !clk->ops->round_rate)

• return -EINVAL;
  

This should return the parents rate if the clock itself does not have a round_rate function. Also, must be || instead of &&

• return clk->ops->round_rate(clk->hw, rate, NULL);

+}

On Tue, Mar 13, 2012 at 04:43:57PM -0700, Turquette, Mike wrote:

On Tue, Mar 13, 2012 at 4:24 AM, Sascha Hauer s.hauer@pengutronix.de wrote:

...

On Sat, Mar 03, 2012 at 12:29:00AM -0800, Mike Turquette wrote:

...

The common clock framework defines a common struct clk useful across most platforms as well as an implementation of the clk api that drivers can use safely for managing clocks.

The net result is consolidation of many different struct clk definitions and platform-specific clock framework implementations.

This patch introduces the common struct clk, struct clk_ops and an implementation of the well-known clock api in include/clk/clk.h. Platforms may define their own hardware-specific clock structure and their own clock operation callbacks, so long as it wraps an instance of struct clk_hw.

See Documentation/clk.txt for more details.

This patch is based on the work of Jeremy Kerr, which in turn was based on the work of Ben Herrenschmidt.

Signed-off-by: Mike Turquette mturquette@linaro.org Signed-off-by: Mike Turquette mturquette@ti.com Cc: Jeremy Kerr jeremy.kerr@canonical.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Arnd Bergman arnd.bergmann@linaro.org Cc: Paul Walmsley paul@pwsan.com Cc: Shawn Guo shawn.guo@freescale.com Cc: Richard Zhao richard.zhao@linaro.org Cc: Saravana Kannan skannan@codeaurora.org Cc: Magnus Damm magnus.damm@gmail.com Cc: Rob Herring rob.herring@calxeda.com Cc: Mark Brown broonie@opensource.wolfsonmicro.com Cc: Linus Walleij linus.walleij@stericsson.com Cc: Stephen Boyd sboyd@codeaurora.org Cc: Amit Kucheria amit.kucheria@linaro.org Cc: Deepak Saxena dsaxena@linaro.org Cc: Grant Likely grant.likely@secretlab.ca Cc: Andrew Lunn andrew@lunn.ch

---

drivers/clk/Kconfig          |   28 +  drivers/clk/Makefile         |    1 +  drivers/clk/clk.c            | 1323 ++++++++++++++++++++++++++++++++++++++++++  include/linux/clk-private.h  |   68 +++  include/linux/clk-provider.h |  169 ++++++  include/linux/clk.h          |   68 ++-  6 files changed, 1652 insertions(+), 5 deletions(-)  create mode 100644 drivers/clk/clk.c  create mode 100644 include/linux/clk-private.h  create mode 100644 include/linux/clk-provider.h

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig index 3912576..18eb8c2 100644 --- a/drivers/clk/Kconfig +++ b/drivers/clk/Kconfig @@ -11,3 +11,31 @@ config HAVE_MACH_CLKDEV

config HAVE_CLK_PREPARE       bool

+menuconfig COMMON_CLK

• bool "Common Clock Framework"
• select HAVE_CLK_PREPARE
• ---help---
• The common clock framework is a single definition of struct
• clk, useful across many platforms, as well as an
• implementation of the clock API in include/linux/clk.h.
• Architectures utilizing the common struct clk should select
• this automatically, but it may be necessary to manually select
• this option for loadable modules requiring the common clock
• framework.
• If in doubt, say "N".

+if COMMON_CLK

+config COMMON_CLK_DEBUG

• bool "DebugFS representation of clock tree"
• depends on COMMON_CLK
• ---help---
• Creates a directory hierchy in debugfs for visualizing the clk
• tree structure.  Each directory contains read-only members
• that export information specific to that clk node: clk_rate,
• clk_flags, clk_prepare_count, clk_enable_count &
• clk_notifier_count.

+endif diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 07613fa..ff362c4 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -1,2 +1,3 @@

obj-$(CONFIG_CLKDEV_LOOKUP)  += clkdev.o +obj-$(CONFIG_COMMON_CLK)     += clk.o diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c new file mode 100644 index 0000000..b979d74 --- /dev/null +++ b/drivers/clk/clk.c @@ -0,0 +1,1323 @@ +/*

• • Copyright (C) 2010-2011 Canonical Ltd jeremy.kerr@canonical.com
• • Copyright (C) 2011-2012 Linaro Ltd mturquette@linaro.org
• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License version 2 as
• • published by the Free Software Foundation.
• • Standard functionality for the common clock API.  See Documentation/clk.txt
• */

+#include <linux/clk-private.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/spinlock.h> +#include <linux/err.h> +#include <linux/list.h> +#include <linux/slab.h>

+static DEFINE_SPINLOCK(enable_lock); +static DEFINE_MUTEX(prepare_lock);

+static HLIST_HEAD(clk_root_list); +static HLIST_HEAD(clk_orphan_list); +static LIST_HEAD(clk_notifier_list);

+/***        debugfs support        ***/

+#ifdef CONFIG_COMMON_CLK_DEBUG +#include <linux/debugfs.h>

+static struct dentry *rootdir; +static struct dentry *orphandir; +static int inited = 0;

+/* caller must hold prepare_lock */ +static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry) +{

• struct dentry *d;
• int ret = -ENOMEM;
• if (!clk || !pdentry) {
• ret = -EINVAL;
• goto out;
• }
• d = debugfs_create_dir(clk->name, pdentry);
• if (!d)
• goto out;
• clk->dentry = d;
• d = debugfs_create_u32("clk_rate", S_IRUGO, clk->dentry,
• (u32 *)&clk->rate);
• if (!d)
• goto err_out;
• d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,
• (u32 *)&clk->flags);
• if (!d)
• goto err_out;
• d = debugfs_create_u32("clk_prepare_count", S_IRUGO, clk->dentry,
• (u32 *)&clk->prepare_count);
• if (!d)
• goto err_out;
• d = debugfs_create_u32("clk_enable_count", S_IRUGO, clk->dentry,
• (u32 *)&clk->enable_count);
• if (!d)
• goto err_out;
• d = debugfs_create_u32("clk_notifier_count", S_IRUGO, clk->dentry,
• (u32 *)&clk->notifier_count);
• if (!d)
• goto err_out;
• ret = 0;
• goto out;

+err_out:

• debugfs_remove(clk->dentry);

+out:

• return ret;

+}

+/* caller must hold prepare_lock */ +static int clk_debug_create_subtree(struct clk *clk, struct dentry *pdentry) +{

• struct clk *child;
• struct hlist_node *tmp;
• int ret = -EINVAL;;
• if (!clk || !pdentry)
• goto out;
• ret = clk_debug_create_one(clk, pdentry);
• if (ret)
• goto out;
• hlist_for_each_entry(child, tmp, &clk->children, child_node)
• clk_debug_create_subtree(child, clk->dentry);
• ret = 0;

+out:

• return ret;

+}

+/**

• • clk_debug_register - add a clk node to the debugfs clk tree
• • @clk: the clk being added to the debugfs clk tree
• • Dynamically adds a clk to the debugfs clk tree if debugfs has been
• • initialized.  Otherwise it bails out early since the debugfs clk tree
• • will be created lazily by clk_debug_init as part of a late_initcall.
• • Caller must hold prepare_lock.  Only clk_init calls this function (so
• • far) so this is taken care.
• */

+static int clk_debug_register(struct clk *clk) +{

• struct clk *parent;
• struct dentry *pdentry;
• int ret = 0;
• if (!inited)
• goto out;
• parent = clk->parent;
• /*
• * Check to see if a clk is a root clk.  Also check that it is
• * safe to add this clk to debugfs
• */
• if (!parent)
• if (clk->flags & CLK_IS_ROOT)
• pdentry = rootdir;
• else
• pdentry = orphandir;
• else
• if (parent->dentry)
• pdentry = parent->dentry;
• else
• goto out;
• ret = clk_debug_create_subtree(clk, pdentry);

+out:

• return ret;

+}

+/**

• • clk_debug_init - lazily create the debugfs clk tree visualization
• • clks are often initialized very early during boot before memory can
• • be dynamically allocated and well before debugfs is setup.
• • clk_debug_init walks the clk tree hierarchy while holding
• • prepare_lock and creates the topology as part of a late_initcall,
• • thus insuring that clks initialized very early will still be
• • represented in the debugfs clk tree.  This function should only be
• • called once at boot-time, and all other clks added dynamically will
• • be done so with clk_debug_register.
• */

+static int __init clk_debug_init(void) +{

• struct clk *clk;
• struct hlist_node *tmp;
• rootdir = debugfs_create_dir("clk", NULL);
• if (!rootdir)
• return -ENOMEM;
• orphandir = debugfs_create_dir("orphans", rootdir);
• if (!orphandir)
• return -ENOMEM;
• mutex_lock(&prepare_lock);
• hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
• clk_debug_create_subtree(clk, rootdir);
• hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
• clk_debug_create_subtree(clk, orphandir);
• inited = 1;
• mutex_unlock(&prepare_lock);
• return 0;

+} +late_initcall(clk_debug_init); +#else +static inline int clk_debug_register(struct clk *clk) { return 0; } +#endif /* CONFIG_COMMON_CLK_DEBUG */

+/***    helper functions   ***/

+inline const char *__clk_get_name(struct clk *clk) +{

• return !clk ? NULL : clk->name;

+}

+inline struct clk_hw *__clk_get_hw(struct clk *clk) +{

• return !clk ? NULL : clk->hw;

+}

+inline u8 __clk_get_num_parents(struct clk *clk) +{

• return !clk ? -EINVAL : clk->num_parents;

+}

+inline struct clk *__clk_get_parent(struct clk *clk) +{

• return !clk ? NULL : clk->parent;

+}

+inline unsigned long __clk_get_rate(struct clk *clk) +{

• return !clk ? -EINVAL : clk->rate;

+}

+inline unsigned long __clk_get_flags(struct clk *clk) +{

• return !clk ? -EINVAL : clk->flags;

+}

+static struct clk *__clk_lookup_subtree(const char *name, struct clk *clk) +{

• struct clk *child;
• struct clk *ret;
• struct hlist_node *tmp;
• if (!strcmp(clk->name, name))
• return clk;
• hlist_for_each_entry(child, tmp, &clk->children, child_node) {
• ret = __clk_lookup_subtree(name, child);
• if (ret)
• return ret;
• }
• return NULL;

+}

+struct clk *__clk_lookup(const char *name) +{

• struct clk *root_clk;
• struct clk *ret;
• struct hlist_node *tmp;

This should have a check for NULL pointers. NULL pointers can happen here if a mux has holes in it. In this case the parent name array would look like this:

{ "parentclk1", "parentclk2", NULL /* reserved */, "parentclk3" }

Without checking for NULL pointers we dereference the NULL pointer here.

I will add the check. I had not considered having NULL as one of the parent names. It seems to me that the only time this would happen is if we are wiring up discrete devices. For instance:

Device A has a fixed-rate clock named "dpll" Device B has a mux clock named "leaf" with parent_names = { "32k", "oscillator", "clkin" }

On a given board, leaf's "pll" parent might map to the output of the dpll clock. I had considered that DT would step in here by creating an intermediate clock with no functional clk_ops that would "connect" these two clocks. The benefit of this is that it is easier to match up clock names when staring at some data sheets. It is common for a downstream device's data sheets to assign names to the external inputs originating from some unknown device; unsurprisingly the data sheet for the device supplying the external upstream clocks often has different names for the output signals than the one in the downstream device's data sheet. Using the method described above it is easy for a person with both data sheets to see how the devices are wired up since all of the clock names are represented by nodes in the clock tree. In short, the final outcome would looking something like:

dpll (device a's driver registered this clock) | clkin (one of device b's possible parents) | (it is a dummy clock from DT since it is board-level topology) | leaf (device b's driver registered this clock)

clkin would have a single parent named "dpll" in this case, and again, it would have no meaningful clk_ops.

A caveat to the above scenario is that parent_names shouldn't have holes in it, but a null pointer check is reasonable anyways.

What do you think? Even if we allow for muxes to have holes in parent_names we'll still have to solve these sort of device integration issues and DT will likely play a roll here. I'll roll in the null pointer check regardless.

Also, do you forsee needing hole in parent_names for any reason other than described above?

I need it only for the case where a some values in the mux are marked as reserved in the datasheet or we simply do not have the corresponding clock in our tree (yet). We could also say that NULL pointers are not allowed in parent arrays, but instead "orphan" or "dummy" should be used. Then __clk_init should check for NULL pointers to make this clear.

Sascha