Current clk_pm_runtime_put is using pm_runtime_put_sync which
is not safe to be called in clk_core_is_enabled as it should
be able to run in atomic context.
Thus use pm_runtime_put instead which is atomic safe.
Cc: Stephen Boyd <[email protected]>
Cc: Michael Turquette <[email protected]>
Cc: Ulf Hansson <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Fixes: 9a34b45397e5 ("clk: Add support for runtime PM")
Signed-off-by: Dong Aisheng <[email protected]>
---
drivers/clk/clk.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 5ec5809..e24968f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -227,7 +227,8 @@ static bool clk_core_is_enabled(struct clk_core *core)
ret = core->ops->is_enabled(core->hw);
done:
- clk_pm_runtime_put(core);
+ if (core->dev)
+ pm_runtime_put(core->dev);
return ret;
}
--
2.7.4
According to design doc, .is_enabled should be protected by enable lock.
Then users don't have to protect it against enable/disable operation
in clock drivers.
See: Documentation/clk.txt
"The enable lock is a spinlock and is held across calls to the .enable,
.disable and .is_enabled operations."
Cc: Stephen Boyd <[email protected]>
Cc: Michael Turquette <[email protected]>
Signed-off-by: Dong Aisheng <[email protected]>
---
drivers/clk/clk.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index e24968f..d6e2d5c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -198,14 +198,19 @@ static bool clk_core_is_prepared(struct clk_core *core)
static bool clk_core_is_enabled(struct clk_core *core)
{
+ unsigned long flags;
bool ret = false;
+ flags = clk_enable_lock();
+
/*
* .is_enabled is only mandatory for clocks that gate
* fall back to software usage counter if .is_enabled is missing
*/
- if (!core->ops->is_enabled)
+ if (!core->ops->is_enabled) {
+ clk_enable_unlock(flags);
return core->enable_count;
+ }
/*
* Check if clock controller's device is runtime active before
@@ -230,6 +235,8 @@ static bool clk_core_is_enabled(struct clk_core *core)
if (core->dev)
pm_runtime_put(core->dev);
+ clk_enable_unlock(flags);
+
return ret;
}
--
2.7.4
On 22 December 2017 at 10:46, Dong Aisheng <[email protected]> wrote:
> Current clk_pm_runtime_put is using pm_runtime_put_sync which
> is not safe to be called in clk_core_is_enabled as it should
> be able to run in atomic context.
>
> Thus use pm_runtime_put instead which is atomic safe.
>
> Cc: Stephen Boyd <[email protected]>
> Cc: Michael Turquette <[email protected]>
> Cc: Ulf Hansson <[email protected]>
> Cc: Marek Szyprowski <[email protected]>
> Fixes: 9a34b45397e5 ("clk: Add support for runtime PM")
> Signed-off-by: Dong Aisheng <[email protected]>
Reviewed-by: Ulf Hansson <[email protected]>
Kind regards
Uffe
> ---
> drivers/clk/clk.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 5ec5809..e24968f 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -227,7 +227,8 @@ static bool clk_core_is_enabled(struct clk_core *core)
>
> ret = core->ops->is_enabled(core->hw);
> done:
> - clk_pm_runtime_put(core);
> + if (core->dev)
> + pm_runtime_put(core->dev);
>
> return ret;
> }
> --
> 2.7.4
>
On 12/22, Dong Aisheng wrote:
> According to design doc, .is_enabled should be protected by enable lock.
> Then users don't have to protect it against enable/disable operation
> in clock drivers.
>
> See: Documentation/clk.txt
> "The enable lock is a spinlock and is held across calls to the .enable,
> .disable and .is_enabled operations."
>
> Cc: Stephen Boyd <[email protected]>
> Cc: Michael Turquette <[email protected]>
> Signed-off-by: Dong Aisheng <[email protected]>
> ---
> drivers/clk/clk.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index e24968f..d6e2d5c 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -198,14 +198,19 @@ static bool clk_core_is_prepared(struct clk_core *core)
>
> static bool clk_core_is_enabled(struct clk_core *core)
> {
> + unsigned long flags;
> bool ret = false;
>
> + flags = clk_enable_lock();
> +
> /*
> * .is_enabled is only mandatory for clocks that gate
> * fall back to software usage counter if .is_enabled is missing
> */
> - if (!core->ops->is_enabled)
> + if (!core->ops->is_enabled) {
> + clk_enable_unlock(flags);
> return core->enable_count;
> + }
>
> /*
> * Check if clock controller's device is runtime active before
> @@ -230,6 +235,8 @@ static bool clk_core_is_enabled(struct clk_core *core)
> if (core->dev)
> pm_runtime_put(core->dev);
>
> + clk_enable_unlock(flags);
> +
> return ret;
> }
It doesn't really make any sense to hold the enable lock inside
the clk_core_is_enabled() function, unless you want to do
something else with the information of the enable state with that
lock held. Otherwise, seeing if a clk is enabled is a one-shot
read of the enabled state, which could just as easily change
after the function returns because the lock is released.
We should update the documentation.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
On 12/22, Dong Aisheng wrote:
> Current clk_pm_runtime_put is using pm_runtime_put_sync which
> is not safe to be called in clk_core_is_enabled as it should
> be able to run in atomic context.
>
> Thus use pm_runtime_put instead which is atomic safe.
>
> Cc: Stephen Boyd <[email protected]>
> Cc: Michael Turquette <[email protected]>
> Cc: Ulf Hansson <[email protected]>
> Cc: Marek Szyprowski <[email protected]>
> Fixes: 9a34b45397e5 ("clk: Add support for runtime PM")
> Signed-off-by: Dong Aisheng <[email protected]>
> ---
Applied to clk-fixes
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
On Tue, Dec 26, 2017 at 05:29:18PM -0800, Stephen Boyd wrote:
> On 12/22, Dong Aisheng wrote:
> > According to design doc, .is_enabled should be protected by enable lock.
> > Then users don't have to protect it against enable/disable operation
> > in clock drivers.
> >
> > See: Documentation/clk.txt
> > "The enable lock is a spinlock and is held across calls to the .enable,
> > .disable and .is_enabled operations."
> >
> > Cc: Stephen Boyd <[email protected]>
> > Cc: Michael Turquette <[email protected]>
> > Signed-off-by: Dong Aisheng <[email protected]>
> > ---
> > drivers/clk/clk.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index e24968f..d6e2d5c 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -198,14 +198,19 @@ static bool clk_core_is_prepared(struct clk_core *core)
> >
> > static bool clk_core_is_enabled(struct clk_core *core)
> > {
> > + unsigned long flags;
> > bool ret = false;
> >
> > + flags = clk_enable_lock();
> > +
> > /*
> > * .is_enabled is only mandatory for clocks that gate
> > * fall back to software usage counter if .is_enabled is missing
> > */
> > - if (!core->ops->is_enabled)
> > + if (!core->ops->is_enabled) {
> > + clk_enable_unlock(flags);
> > return core->enable_count;
> > + }
> >
> > /*
> > * Check if clock controller's device is runtime active before
> > @@ -230,6 +235,8 @@ static bool clk_core_is_enabled(struct clk_core *core)
> > if (core->dev)
> > pm_runtime_put(core->dev);
> >
> > + clk_enable_unlock(flags);
> > +
> > return ret;
> > }
>
> It doesn't really make any sense to hold the enable lock inside
> the clk_core_is_enabled() function, unless you want to do
> something else with the information of the enable state with that
> lock held. Otherwise, seeing if a clk is enabled is a one-shot
> read of the enabled state, which could just as easily change
> after the function returns because the lock is released.
>
> We should update the documentation.
>
Yes, you're absolutely right.
I could draft a patch to update it later.
Thanks
Regards
Dong Aisheng
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
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