linux-kernel - Re: [PATCH] pwm: mtk_disp: fix disp

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Message-ID: <55c3a448-e6c6-5e04-2cee-b2a18f0033e3@baylibre.com>
Date:   Thu, 6 Jul 2023 14:29:11 +0200
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     Shuijing Li <shuijing.li@...iatek.com>, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de, matthias.bgg@...il.com,
        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] pwm: mtk_disp: fix disp_pwm coverity issue



On 06/07/2023 12:04, Shuijing Li wrote:
> There is a coverity issue in the original mtk_disp_pwm_get_state()
> function. In function call DIV64_U64_ROUND_UP, division by expression
> Which may be zero has undefined behavior.
> Fix this accordingly.
> 
> Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
> ---
>   drivers/pwm/pwm-mtk-disp.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 79e321e96f56..ca00058a6ef4 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -196,6 +196,14 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip,
>   		return err;
>   	}
>   
> +	rate = clk_get_rate(mdp->clk_main);
> +	if (rate <= 0) {
> +		dev_err(chip->dev, "Can't get rate: %pe\n", ERR_PTR(rate));
> +		clk_disable_unprepare(mdp->clk_mm);
> +		clk_disable_unprepare(mdp->clk_main);
> +		return err;
> +	}
> +
>   	/*
>   	 * Apply DISP_PWM_DEBUG settings to choose whether to enable or disable
>   	 * registers double buffer and manual commit to working register before
> @@ -206,7 +214,6 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip,
>   					 mdp->data->bls_debug_mask,
>   					 mdp->data->bls_debug_mask);
>   
> -	rate = clk_get_rate(mdp->clk_main);
>   	con0 = readl(mdp->base + mdp->data->con0);
>   	con1 = readl(mdp->base + mdp->data->con1);
>   	pwm_en = readl(mdp->base + DISP_PWM_EN);

IMHO, it should be done int the function `mtk_disp_pwm_apply` too.
Do you agree ?

-- 
Regards,
Alexandre