linux-kernel - Re: [PATCH] phy: mediatek: fix returning garbage

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Date:   Fri, 14 Apr 2023 08:49:21 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Tom Rix <trix@...hat.com>
Cc:     chunkuang.hu@...nel.org, p.zabel@...gutronix.de,
        chunfeng.yun@...iatek.com, vkoul@...nel.org, kishon@...nel.org,
        matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        ndesaulniers@...gle.com, granquet@...libre.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] phy: mediatek: fix returning garbage

On Fri, Apr 14, 2023 at 08:22:53AM -0400, Tom Rix wrote:
> clang reports
> drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c:298:6: error: variable
>   'ret' is uninitialized when used here [-Werror,-Wuninitialized]
>         if (ret)
>             ^~~
> ret should have been set by the preceding call to mtk_hdmi_pll_set_hw.
> 
> Fixes: 45810d486bb4 ("phy: mediatek: add support for phy-mtk-hdmi-mt8195")
> Signed-off-by: Tom Rix <trix@...hat.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Angelo brought up a good point on another patch to fix this issue that
we should probably be returning ret instead of unconditionally returning
-EINVAL but it sounds like it does not really matter at the moment since
mtk_hdmi_pll_set_hw() can only return -EINVAL or 0.

https://lore.kernel.org/ada769e0-0141-634f-3753-eb3a50f0eee3@collabora.com/

> ---
>  drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> index abfc077fb0a8..c63294e451d6 100644
> --- a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> +++ b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> @@ -292,9 +292,9 @@ static int mtk_hdmi_pll_calc(struct mtk_hdmi_phy *hdmi_phy, struct clk_hw *hw,
>  	if (!(digital_div <= 32 && digital_div >= 1))
>  		return -EINVAL;
>  
> -	mtk_hdmi_pll_set_hw(hw, PLL_PREDIV, fbkdiv_high, fbkdiv_low,
> -			    PLL_FBKDIV_HS3, posdiv1, posdiv2, txprediv,
> -			    txposdiv, digital_div);
> +	ret = mtk_hdmi_pll_set_hw(hw, PLL_PREDIV, fbkdiv_high, fbkdiv_low,
> +				  PLL_FBKDIV_HS3, posdiv1, posdiv2, txprediv,
> +				  txposdiv, digital_div);
>  	if (ret)
>  		return -EINVAL;
>  
> -- 
> 2.27.0
>