linux-kernel - Re: [PATCH] drm/amd: Guard IS_OLD_GCC assignment with CONFIG_CC_IS

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Message-ID: <CAKwvOdkrD4WuZzUnBc2LeCjLVAumBCKXJdyr=k=dPDX1BsMhOg@mail.gmail.com>
Date:   Thu, 30 Sep 2021 10:29:49 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] drm/amd: Guard IS_OLD_GCC assignment with CONFIG_CC_IS_GCC

On Thu, Sep 30, 2021 at 9:02 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> cc-ifversion only works for GCC, as clang pretends to be GCC 4.2.1 for
> glibc compatibility, which means IS_OLD_GCC will get set and unsupported
> flags will be passed to clang when building certain code within the DCN
> files:
>
> clang-14: error: unknown argument: '-mpreferred-stack-boundary=4'
> make[5]: *** [scripts/Makefile.build:277: drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_resource.o] Error 1
>
> Guard the call to cc-ifversion with CONFIG_CC_IS_GCC so that everything
> continues to work properly. See commit 00db297106e8 ("drm/amdgpu: fix stack
> alignment ABI mismatch for GCC 7.1+") for more context.
>
> Fixes: ff7e396f822f ("drm/amd/display: add cyan_skillfish display support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1468
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

$ grep -rn "ifdef IS_OLD_GCC" drivers/gpu/drm/amd/display/dc/ | wc -l
11

It's probably time to put this pattern in a Makefile under scripts/
and include it in all of these Makefiles.  Anything to minimize the
amount of code that has to be carried forward to new subdirs.

> ---
>  drivers/gpu/drm/amd/display/dc/dcn201/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/Makefile b/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> index d98d69705117..96cbd4ccd344 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn201/Makefile
> @@ -14,9 +14,11 @@ ifdef CONFIG_PPC64
>  CFLAGS_$(AMDDALPATH)/dc/dcn201/dcn201_resource.o := -mhard-float -maltivec
>  endif
>
> +ifdef CONFIG_CC_IS_GCC
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> +endif
>
>  ifdef CONFIG_X86
>  ifdef IS_OLD_GCC
>
> base-commit: b47b99e30cca8906753c83205e8c6179045dd725
> --
> 2.33.0.591.gddb1055343
>


-- 
Thanks,
~Nick Desaulniers