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  3. [PATCH 0/2] Fix mtk-hdmi-mt8195 unitialized variable usage and clock rate calculation
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[PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc

Guillaume Ranquet posted 2 patches 2 years, 9 months ago
There is a newer version of this series
[PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc
Posted by Guillaume Ranquet 2 years, 9 months ago 
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;
 
 	return 0;

-- 
2.39.2
Re: [PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc
Posted by AngeloGioacchino Del Regno 2 years, 9 months ago 
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
Re: [PATCH 1/2] phy: mediatek: hdmi: mt8195: fix uninitialized variable usage in pll_calc
Posted by Guillaume Ranquet 2 years, 9 months ago 
On Fri, 14 Apr 2023 12:31, AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com> wrote:
>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
>

Hi Angelo,
I was maybe a bit too quick on fixing this that way.
Anyway it doesn't change a thing as mtk_hdmi_pll_set_hw() eitheir
returns 0 or -EINVAL.
But I agree that the logic is dubious and propagating the return value
is the right thing
to do.

I see that Arnd and Tom posted versions that you might prefer:

https://lore.kernel.org/linux-phy/20230414075842.4006164-1-arnd@kernel.org/
https://lore.kernel.org/linux-phy/20230414122253.3171524-1-trix@redhat.com/

Thx,
Guillaume.

>	ret = mtk_hdmi_pll_set_hw(....)
>	if (ret)
>		return ret;
>
>	return 0;
>
>
>Regards,
>Angelo

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