[PATCH] PM / clk: Do not __clk_get passed in clock-references

[PATCH] PM / clk: Do not __clk_get passed in clock-references

[Heiko Stübner]

From: Stephen Boyd <sboyd@codeaurora.org>

Clock references are on a per-user basis now, so they are not supposed
to be refcounted by itself anymore. Therefore multiple cascaded get and
put calls will fail.

When a clock reference gets passed into pm_clk_add_clk we can assume
that the pm clock handling will take control of the clock reference,
so after this functions returns the caller should've given up control
of that handle.

So remove the additional call to __clk_get() in __pm_clk_add().

The only current user of pm_clk_add_clk is drivers/clk/shmobile/clk-mstp.c
which already follows this paradigm by only getting the clock but not
puting it after passing the reference into pm_clk_add_clk.

In the error case the caller is expected to clean up the clock, as it
may very well try to do something different if pm_clk_add_clk() fails.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
[add commit-message]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
Hi Rafael, Pavel,

if that looks acceptable to you, it would be cool if you could ack the
patch and allow me to put it in front of [0] or alternatively
provide a stable-branch I could include.

Thanks
Heiko

[0] https://git.kernel.org/cgit/linux/kernel/git/mmind/linux-rockchip.git/commit/?h=v4.4-armsoc/drivers

 drivers/base/power/clock_ops.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index 652b5a3..6ce7693 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -93,7 +93,7 @@ static int __pm_clk_add(struct device *dev, const char *con_id,
 			return -ENOMEM;
 		}
 	} else {
-		if (IS_ERR(clk) || !__clk_get(clk)) {
+		if (IS_ERR(clk)) {
 			kfree(ce);
 			return -ENOENT;
 		}
@@ -127,7 +127,9 @@ int pm_clk_add(struct device *dev, const char *con_id)
  * @clk: Clock pointer
  *
  * Add the clock to the list of clocks used for the power management of @dev.
- * It will increment refcount on clock pointer, use clk_put() on it when done.
+ * The power-management code will take control of the clock reference, so
+ * callers should not call clk_put() on @clk after this function sucessfully
+ * returned.
  */
 int pm_clk_add_clk(struct device *dev, struct clk *clk)
 {
-- 
2.5.3

Re: [PATCH] PM / clk: Do not __clk_get passed in clock-references

[Rafael J. Wysocki]

On Thursday, October 01, 2015 09:05:09 PM Heiko Stübner wrote:
> From: Stephen Boyd <sboyd@codeaurora.org>
> 
> Clock references are on a per-user basis now, so they are not supposed
> to be refcounted by itself anymore. Therefore multiple cascaded get and
> put calls will fail.
> 
> When a clock reference gets passed into pm_clk_add_clk we can assume
> that the pm clock handling will take control of the clock reference,
> so after this functions returns the caller should've given up control
> of that handle.
> 
> So remove the additional call to __clk_get() in __pm_clk_add().
> 
> The only current user of pm_clk_add_clk is drivers/clk/shmobile/clk-mstp.c
> which already follows this paradigm by only getting the clock but not
> puting it after passing the reference into pm_clk_add_clk.
> 
> In the error case the caller is expected to clean up the clock, as it
> may very well try to do something different if pm_clk_add_clk() fails.
> 
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> [add commit-message]
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
> Hi Rafael, Pavel,
> 
> if that looks acceptable to you, it would be cool if you could ack the
> patch and allow me to put it in front of [0] or alternatively
> provide a stable-branch I could include.

OK

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>


> [0] https://git.kernel.org/cgit/linux/kernel/git/mmind/linux-rockchip.git/commit/?h=v4.4-armsoc/drivers
> 
>  drivers/base/power/clock_ops.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
> index 652b5a3..6ce7693 100644
> --- a/drivers/base/power/clock_ops.c
> +++ b/drivers/base/power/clock_ops.c
> @@ -93,7 +93,7 @@ static int __pm_clk_add(struct device *dev, const char *con_id,
>  			return -ENOMEM;
>  		}
>  	} else {
> -		if (IS_ERR(clk) || !__clk_get(clk)) {
> +		if (IS_ERR(clk)) {
>  			kfree(ce);
>  			return -ENOENT;
>  		}
> @@ -127,7 +127,9 @@ int pm_clk_add(struct device *dev, const char *con_id)
>   * @clk: Clock pointer
>   *
>   * Add the clock to the list of clocks used for the power management of @dev.
> - * It will increment refcount on clock pointer, use clk_put() on it when done.
> + * The power-management code will take control of the clock reference, so
> + * callers should not call clk_put() on @clk after this function sucessfully
> + * returned.
>   */
>  int pm_clk_add_clk(struct device *dev, struct clk *clk)
>  {
>