Re: [PATCH v5 3/4] clk: introduce the common clock framework

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