[PATCH] pwm: mtk_disp: Fix the disable flow of disp_pwm

[PATCH] pwm: mtk_disp: Fix the disable flow of disp_pwm

[Shuijing Li]

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@mediatek.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);
 		}
-- 
2.40.1

Re: [PATCH] pwm: mtk_disp: Fix the disable flow of disp_pwm

[Uwe Kleine-König]

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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@mediatek.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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