linux-kernel - Re: [PATCH] pwm: mtk_disp: Fix the disable flow of disp

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Date:   Mon, 15 May 2023 16:03:46 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Shuijing Li <shuijing.li@...iatek.com>
Cc:     thierry.reding@...il.com, matthias.bgg@...il.com,
        angelogioacchino.delregno@...labora.com,
        devicetree@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        jitao.shi@...iatek.com
Subject: Re: [PATCH] pwm: mtk_disp: Fix the disable flow of disp_pwm

On Mon, May 15, 2023 at 02:18:45PM +0800, Shuijing Li wrote:
> There is a flow error in the original mtk_disp_pwm_apply() function.
> If this function is called when the clock is disabled, there will be a
> chance to operate the disp_pwm register, resulting in disp_pwm exception.
> Fix this accordingly.
> 
> Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
> ---
>  drivers/pwm/pwm-mtk-disp.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 79e321e96f56..cb699fa9a5ae 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -80,10 +80,9 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  		return -EINVAL;
>  
>  	if (!state->enabled) {
> -		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> -					 0x0);
> -
>  		if (mdp->enabled) {
> +			mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN,
> +						 mdp->data->enable_mask, 0x0);
>  			clk_disable_unprepare(mdp->clk_mm);
>  			clk_disable_unprepare(mdp->clk_main);

Instead of

	if (A) {
		if (B) {
			something();
		}
	}

you can make this

	if (A && B) {
		something();
	}

Otherwise looks ok.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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