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Message-ID: <c657222a816d95b09d220569db1fdde2be747e7f.camel@mediatek.com>
Date: Mon, 16 Jan 2023 07:51:29 +0000
From: Chunfeng Yun (云春峰)
<Chunfeng.Yun@...iatek.com>
To: "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>
CC: "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
"linux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"lkp@...el.com" <lkp@...el.com>,
"nathan@...nel.org" <nathan@...nel.org>,
"kishon@...nel.org" <kishon@...nel.org>,
Eddie Hung (洪正鑫)
<Eddie.Hung@...iatek.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"vkoul@...nel.org" <vkoul@...nel.org>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
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<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v6 1/3] phy: mediatek: fix build warning caused by clang
On Fri, 2023-01-13 at 10:36 -0800, Nick Desaulniers wrote:
> On Wed, Jan 4, 2023 at 5:26 AM Chunfeng Yun <
> chunfeng.yun@...iatek.com> wrote:
> >
> > Remove the temporary @mask_, this may cause build warning when use
> > clang
> > compiler for powerpc, but can't reproduce it when compile for
> > arm64.
> > the build warning is -Wtautological-constant-out-of-range-compare,
> > and
> > caused by
> > "BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask)"
>
> Can you please include the text of the observed warning?
Ok, will add more logs
>
> >
> > After removing @mask_, there is a "CHECK:MACRO_ARG_REUSE" when run
> > checkpatch.pl, due to @mask is constant, no reuse problem will
> > happen.
> >
> > Fixes: 84513eccd678 ("phy: mediatek: fix build warning of
> > FIELD_PREP()")
>
> Uh, why was 84513eccd678 sent/reviewed/merged if it didn't fix the
> issue correctly in the first place?
Sorry, I can't reproduce it, but make sure no such issue happens on arm
arch using gcc/clang. MTK only uses arm/mips arch, it's difficult for
me to set up clang cross compiler for other archs in office.
>
> Is the issue perhaps that your mask isn't wide enough in the first
> place, and should be?
the masks are usually created by GENMASK macro;
There is no warning when build for arm64 using clang.
> See:
> commit cfd6fb45cfaf ("crypto: ccree - avoid out-of-range warnings
> from clang")
> for inspiration.
Ok, I'll do it
>
> > Reported-by: kernel test robot <lkp@...el.com>
>
> Can you please include the Link: tag to the lore URL of the report?
Ok, thanks a lot
>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> > v6: modify the title
> > v5: no changes
> > v4 new patch, I'm not sure it can fix build warning, due to I don't
> > cross compile
> > it for powerpc using clang in office.
> > ---
> > drivers/phy/mediatek/phy-mtk-io.h | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/phy/mediatek/phy-mtk-io.h
> > b/drivers/phy/mediatek/phy-mtk-io.h
> > index d20ad5e5be81..58f06db822cb 100644
> > --- a/drivers/phy/mediatek/phy-mtk-io.h
> > +++ b/drivers/phy/mediatek/phy-mtk-io.h
> > @@ -39,8 +39,8 @@ static inline void mtk_phy_update_bits(void
> > __iomem *reg, u32 mask, u32 val)
> > /* field @mask shall be constant and continuous */
> > #define mtk_phy_update_field(reg, mask, val) \
> > ({ \
> > - typeof(mask) mask_ = (mask); \
> > - mtk_phy_update_bits(reg, mask_, FIELD_PREP(mask_, val)); \
> > + BUILD_BUG_ON_MSG(!__builtin_constant_p(mask), "mask is not
> > constant"); \
> > + mtk_phy_update_bits(reg, mask, FIELD_PREP(mask, val)); \
> > })
> >
> > #endif
> > --
> > 2.18.0
> >
>
>
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