linux-kernel - Re: [PATCH] drm/mediatek: Fix unused-but-set variable warning

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Date:   Tue, 28 Dec 2021 15:53:55 +0100
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Miles Chen <miles.chen@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/mediatek: Fix unused-but-set variable warning



On 28/12/2021 10:25, Miles Chen wrote:
> Fix unused-but-set variable warning:
> drivers/gpu/drm/mediatek/mtk_cec.c:85:6: warning: variable 'tmp' set but not used [-Wunused-but-set-variable]
> 

Actually we ignore the value passed to mtk_cec_mask. In case of
mtk_cec_mask(cec, CEC_CKGEN, 0 | CEC_32K_PDN, PDN | CEC_32K_PDN);


We are not setting CEC_32K_PDN. I wonder which side effect will it have to set 
that bit.

Anyway, if it's the right thing to do, we should add:

Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support")


Regards,
Matthias

> Signed-off-by: Miles Chen <miles.chen@...iatek.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_cec.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_cec.c b/drivers/gpu/drm/mediatek/mtk_cec.c
> index e9cef5c0c8f7..cdfa648910b2 100644
> --- a/drivers/gpu/drm/mediatek/mtk_cec.c
> +++ b/drivers/gpu/drm/mediatek/mtk_cec.c
> @@ -85,7 +85,7 @@ static void mtk_cec_mask(struct mtk_cec *cec, unsigned int offset,
>   	u32 tmp = readl(cec->regs + offset) & ~mask;
>   
>   	tmp |= val & mask;
> -	writel(val, cec->regs + offset);
> +	writel(tmp, cec->regs + offset);
>   }
>   
>   void mtk_cec_set_hpd_event(struct device *dev,
>