linux-kernel - Re: [PATCHv2 3/6] thermal: exynos: Check before clk_disable

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Message-ID: <7c479bdb-4bf7-68a5-c6e7-20dc19b91dc8@linaro.org>
Date:   Sun, 15 May 2022 11:43:15 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Anand Moon <linux.amoon@...il.com>,
        Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        linux-pm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 3/6] thermal: exynos: Check before
 clk_disable_unprepare() not needed

On 15/05/2022 08:41, Anand Moon wrote:
> All code in clk_disable_unprepare() already checks the clk ptr using
> IS_ERR_OR_NULL so there is no need to check it again before calling it.
> A lot of other drivers already rely on this behaviour, so it's safe
> to do so here.
> 
> Cc: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> ---
> v1: improve the commit message
> ---
>  drivers/thermal/samsung/exynos_tmu.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
> index 1ef90dc52c08..58ff1b577c47 100644
> --- a/drivers/thermal/samsung/exynos_tmu.c
> +++ b/drivers/thermal/samsung/exynos_tmu.c
> @@ -289,8 +289,7 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
>  
>  	mutex_lock(&data->lock);
>  	clk_enable(data->clk);
> -	if (!IS_ERR(data->clk_sec))
> -		clk_enable(data->clk_sec);
> +	clk_enable(data->clk_sec);

You say that clk_enable() checks for IS_ERR_OR_NULL. Where? I see only
check for non-null case and then immediately taking clk prepare lock.

This looks buggy... did you test it?

Best regards,
Krzysztof