* [PATCH v3] drm/mediatek: Fix unused-but-set variable warning
@ 2021-12-30 9:36 Miles Chen
2021-12-30 12:29 ` Matthias Brugger
0 siblings, 1 reply; 4+ messages in thread
From: Miles Chen @ 2021-12-30 9:36 UTC (permalink / raw)
To: Chun-Kuang Hu, Philipp Zabel, David Airlie, Daniel Vetter,
Matthias Brugger, Nathan Chancellor, Nick Desaulniers, Jie Qiu,
Junzhi Zhao
Cc: Miles Chen, Zhiqiang Lin, CK Hu, dri-devel, linux-mediatek,
linux-arm-kernel, linux-kernel, llvm
clang reports a 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]
In current implementation, mtk_cec_mask() writes val into target register
and ignores the mask. After talking to our hdmi experts, mtk_cec_mask()
should read a register, clean only mask bits, and update (val | mask) bits
to the register.
Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support")
Cc: Zhiqiang Lin <zhiqiang.lin@mediatek.com>
Cc: CK Hu <ck.hu@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
---
Change since v1:
add Fixes tag
Change since v2:
add explanation of mtk_cec_mask()
Change-Id: Iec6402b0532942f4d0e8bc56817eb87b95c03fad
---
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,
--
2.18.0
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v3] drm/mediatek: Fix unused-but-set variable warning
2021-12-30 9:36 [PATCH v3] drm/mediatek: Fix unused-but-set variable warning Miles Chen
@ 2021-12-30 12:29 ` Matthias Brugger
0 siblings, 0 replies; 4+ messages in thread
From: Matthias Brugger @ 2021-12-30 12:29 UTC (permalink / raw)
To: Miles Chen, Chun-Kuang Hu, Philipp Zabel, David Airlie,
Daniel Vetter, Nathan Chancellor, Nick Desaulniers, Jie Qiu,
Junzhi Zhao
Cc: Zhiqiang Lin, CK Hu, dri-devel, linux-mediatek, linux-arm-kernel,
linux-kernel, llvm
On 30/12/2021 10:36, Miles Chen wrote:
> clang reports a 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]
>
> In current implementation, mtk_cec_mask() writes val into target register
> and ignores the mask. After talking to our hdmi experts, mtk_cec_mask()
> should read a register, clean only mask bits, and update (val | mask) bits
> to the register.
>
> Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support")
>
> Cc: Zhiqiang Lin <zhiqiang.lin@mediatek.com>
> Cc: CK Hu <ck.hu@mediatek.com>
> Cc: Matthias Brugger <matthias.bgg@gmail.com>
>
> Signed-off-by: Miles Chen <miles.chen@mediatek.com>
I'm still not happy with the commit subject, I think it is misleading. Clang
only helped to find the bug, but the we are fixing something else, that's not
just a clang warning. But I don't want to nit-pick too much so:
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
>
> ---
>
> Change since v1:
> add Fixes tag
>
> Change since v2:
> add explanation of mtk_cec_mask()
>
> Change-Id: Iec6402b0532942f4d0e8bc56817eb87b95c03fad
> ---
> 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,
>
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] drm/mediatek: Fix unused-but-set variable warning
@ 2021-12-28 14:53 Matthias Brugger
2022-01-02 23:46 ` [PATCH v3] " miles.chen
0 siblings, 1 reply; 4+ messages in thread
From: Matthias Brugger @ 2021-12-28 14:53 UTC (permalink / raw)
To: Miles Chen, Chun-Kuang Hu, Philipp Zabel, David Airlie, Daniel Vetter
Cc: dri-devel, linux-mediatek, linux-arm-kernel, linux-kernel
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@mediatek.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,
>
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v3] drm/mediatek: Fix unused-but-set variable warning
2021-12-28 14:53 [PATCH] " Matthias Brugger
@ 2022-01-02 23:46 ` miles.chen
2022-01-07 1:40 ` Miles Chen
0 siblings, 1 reply; 4+ messages in thread
From: miles.chen @ 2022-01-02 23:46 UTC (permalink / raw)
To: matthias.bgg, Nathan Chancellor, Nick Desaulniers, Jie Qiu,
Junzhi Zhao, Philipp Zabel
Cc: airlied, chunkuang.hu, daniel, dri-devel, linux-arm-kernel,
linux-kernel, linux-mediatek, miles.chen, llvm
> I'm still not happy with the commit subject, I think it is misleading. Clang
> only helped to find the bug, but the we are fixing something else, that's not
> just a clang warning. But I don't want to nit-pick too much so:
>
> Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
thanks. I think you are right.
I will change the subject to "drm/mediatek: Fix mtk_cec_mask()", remove the
clang part and submit patch v4.
e.g,
"""
drm/mediatek: Fix mtk_cec_mask()
In current implementation, mtk_cec_mask() writes val into target register
and ignores the mask. After talking to our hdmi experts, mtk_cec_mask()
should read a register, clean only mask bits, and update (val | mask) bits
to the register.
Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support")
"""
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v3] drm/mediatek: Fix unused-but-set variable warning
2022-01-02 23:46 ` [PATCH v3] " miles.chen
@ 2022-01-07 1:40 ` Miles Chen
0 siblings, 0 replies; 4+ messages in thread
From: Miles Chen @ 2022-01-07 1:40 UTC (permalink / raw)
To: matthias.bgg
Cc: airlied, chunkuang.hu, daniel, dri-devel, jie.qiu, junzhi.zhao,
linux-arm-kernel, linux-kernel, linux-mediatek, llvm, p.zabel
Hi Matthias,
>> I'm still not happy with the commit subject, I think it is misleading. Clang
>> only helped to find the bug, but the we are fixing something else, that's not
>> just a clang warning. But I don't want to nit-pick too much so:
>>
>> Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
> thanks. I think you are right.
> I will change the subject to "drm/mediatek: Fix mtk_cec_mask()", remove the
> clang part and submit patch v4.
I posted patch v4 https://lore.kernel.org/linux-mediatek/20220103054706.8072-1-miles.chen@mediatek.com/
without your reviewed-by tag.
Would you mind taking a look at the patch?
Miles
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-01-07 1:41 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-12-30 9:36 [PATCH v3] drm/mediatek: Fix unused-but-set variable warning Miles Chen
2021-12-30 12:29 ` Matthias Brugger
-- strict thread matches above, loose matches on Subject: below --
2021-12-28 14:53 [PATCH] " Matthias Brugger
2022-01-02 23:46 ` [PATCH v3] " miles.chen
2022-01-07 1:40 ` Miles Chen
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).