linux-kernel - Re: [PATCH v2] pwm: mtk_disp: Fix the disable flow of disp

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Message-ID: <0ff74fff-9e48-e2a6-617c-13d4cfc2e157@gmail.com>
Date:   Mon, 29 May 2023 12:43:22 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Shuijing Li <shuijing.li@...iatek.com>, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de,
        angelogioacchino.delregno@...labora.com
Cc:     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 v2] pwm: mtk_disp: Fix the disable flow of disp_pwm



On 18/05/2023 13:52, 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>

We are missing a fixes tag here.
Fixes: 888a623db5d0 ("pwm: mtk-disp: Implement atomic API .apply()")


with that:
Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>

> ---
> Changes in v2:
> Use
> if (A && B) {
> 	something();
> }
> instead of
> if (A) {
> 	if (B) {
> 		something();
> 	}
> }
> per suggestion from the previous thread:
> https://lore.kernel.org/lkml/20230515140346.bxeu6xewi6a446nd@pengutronix.de/
> ---
>   drivers/pwm/pwm-mtk-disp.c | 13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 79e321e96f56..2401b6733241 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -79,14 +79,11 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>   	if (state->polarity != PWM_POLARITY_NORMAL)
>   		return -EINVAL;
>   
> -	if (!state->enabled) {
> -		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> -					 0x0);
> -
> -		if (mdp->enabled) {
> -			clk_disable_unprepare(mdp->clk_mm);
> -			clk_disable_unprepare(mdp->clk_main);
> -		}
> +	if (!state->enabled && 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);
>   
>   		mdp->enabled = false;
>   		return 0;