Re: [PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
To: Guillaume Ranquet <granquet@baylibre.com>,
	Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	Vinod Koul <vkoul@kernel.org>,
	Kishon Vijay Abraham I <kishon@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>
Cc: dri-devel@lists.freedesktop.org,
	linux-mediatek@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org,
	kernel test robot <lkp@intel.com>
Subject: Re: [PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc
Date: Fri, 14 Apr 2023 12:31:47 +0200	[thread overview]
Message-ID: <ada769e0-0141-634f-3753-eb3a50f0eee3@collabora.com> (raw)
In-Reply-To: <20230413-fixes-for-mt8195-hdmi-phy-v1-1-b8482458df0d@baylibre.com>

Il 13/04/23 14:46, Guillaume Ranquet ha scritto:
> The ret variable in mtk_hdmi_pll_calc() was used unitialized as reported
> by the kernel test robot.
> 
> Fix the issue by removing the variable altogether and testing out the
> return value of mtk_hdmi_pll_set_hw()
> 
> Fixes: 45810d486bb44 ("phy: mediatek: add support for phy-mtk-hdmi-mt8195")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> ---
>   drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> index abfc077fb0a8..e10da6c4147e 100644
> --- a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> +++ b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> @@ -213,7 +213,7 @@ static int mtk_hdmi_pll_calc(struct mtk_hdmi_phy *hdmi_phy, struct clk_hw *hw,
>   	u64 tmds_clk, pixel_clk, da_hdmitx21_ref_ck, ns_hdmipll_ck, pcw;
>   	u8 txpredivs[4] = { 2, 4, 6, 12 };
>   	u32 fbkdiv_low;
> -	int i, ret;
> +	int i;
>   
>   	pixel_clk = rate;
>   	tmds_clk = pixel_clk;
> @@ -292,10 +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,
> +	if (mtk_hdmi_pll_set_hw(hw, PLL_PREDIV, fbkdiv_high, fbkdiv_low,
>   			    PLL_FBKDIV_HS3, posdiv1, posdiv2, txprediv,
> -			    txposdiv, digital_div);
> -	if (ret)
> +			    txposdiv, digital_div))
>   		return -EINVAL;
>   

I don't get why we're returning -EINVAL unconditionally in the first place, here.

Function mtk_hdmi_pll_set_hw() should return zero or a negative error number: in
that case, the previous *intention* was fine, so this should be

	ret = mtk_hdmi_pll_set_hw(....)
	if (ret)
		return ret;

	return 0;

Regards,
Angelo

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