linux-kernel - Re: [PATCH] PM / clk: Do not __clk

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Message-ID: <7126718.0ZHn4yyKKA@vostro.rjw.lan>
Date:	Mon, 05 Oct 2015 22:54:13 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	Pavel Machek <pavel@....cz>, Stephen Boyd <sboyd@...eaurora.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / clk: Do not __clk_get passed in clock-references

On Thursday, October 01, 2015 09:05:09 PM Heiko Stübner wrote:
> From: Stephen Boyd <sboyd@...eaurora.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@...eaurora.org>
> [add commit-message]
> Signed-off-by: Heiko Stuebner <heiko@...ech.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@...el.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)
>  {
> 

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