Quoting Bill Huang (2013-03-19 06:28:32)
Add notifier calls in clk_prepare and clk_unprepare so drivers which are interested in knowing that clk_prepare/unprepare call can act accordingly.
The existing "clk_set_rate" notifier is not enough for normal DVFS inplementation since clock might be enabled/disabled at runtime. Adding these notifiers is useful on DVFS core which take clk_prepare as a hint on that the notified clock might be enabled later so it can raise voltage to a safe level before enabling the clock, and take clk_unprepare as a hint that the clock has been disabled and is safe to lower the voltage.
The added notifier events are:
PRE_CLK_PREPARE POST_CLK_PREPARE ABORT_CLK_PREPARE PRE_CLK_UNPREPARE POST_CLK_UNPREPARE
Signed-off-by: Bill Huang bilhuang@nvidia.com
Is this a resend or a new version? It would be nice to put RESEND in the patch $SUBJECT or put a changelog from previous patches under the "---" below.
I'm still not sure about this approach. Based on feedback I got from Linaro Connect I am not convinced that scaling voltage through clk rate-change notifiers is the right way to go. As I understand it this patch only exists for that single purpose, so if the voltage-notifier idea gets dropped then I will not take this patch in.
Regards, Mike
drivers/clk/clk.c | 88 ++++++++++++++++++++++++++++++--------------------- include/linux/clk.h | 5 +++ 2 files changed, 57 insertions(+), 36 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index ed87b24..ac07c6e 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -516,6 +516,42 @@ struct clk *__clk_lookup(const char *name) /*** clk api ***/ +/**
- __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;+}
void __clk_unprepare(struct clk *clk) { if (!clk) @@ -549,7 +585,14 @@ void __clk_unprepare(struct clk *clk) void clk_unprepare(struct clk *clk) { mutex_lock(&prepare_lock);
if (clk->notifier_count)__clk_notify(clk, PRE_CLK_UNPREPARE, clk->rate, clk->rate);__clk_unprepare(clk);if (clk->notifier_count)__clk_notify(clk, POST_CLK_UNPREPARE, clk->rate, clk->rate);mutex_unlock(&prepare_lock);} EXPORT_SYMBOL_GPL(clk_unprepare); @@ -597,7 +640,16 @@ int clk_prepare(struct clk *clk) int ret; mutex_lock(&prepare_lock);
if (clk->notifier_count)__clk_notify(clk, PRE_CLK_PREPARE, clk->rate, clk->rate);ret = __clk_prepare(clk);if (!ret && clk->notifier_count)__clk_notify(clk, POST_CLK_PREPARE, clk->rate, clk->rate);else if (clk->notifier_count)__clk_notify(clk, ABORT_CLK_PREPARE, clk->rate, clk->rate);mutex_unlock(&prepare_lock);return ret; @@ -749,42 +801,6 @@ long clk_round_rate(struct clk *clk, unsigned long rate) 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)
diff --git a/include/linux/clk.h b/include/linux/clk.h index b3ac22d..41d567d 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -43,6 +43,11 @@ struct clk; #define PRE_RATE_CHANGE BIT(0) #define POST_RATE_CHANGE BIT(1) #define ABORT_RATE_CHANGE BIT(2) +#define PRE_CLK_PREPARE BIT(3) +#define POST_CLK_PREPARE BIT(4) +#define ABORT_CLK_PREPARE BIT(5) +#define PRE_CLK_UNPREPARE BIT(6) +#define POST_CLK_UNPREPARE BIT(7) /**
- struct clk_notifier - associate a clk with a notifier
-- 1.7.9.5