linux-kernel - Re: [PATCH] drm/amd/display: Allow building DC with clang on RISC-V

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Message-ID: <20230718163953.GA1279879@dev-arch.thelio-3990X>
Date:   Tue, 18 Jul 2023 09:39:53 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Samuel Holland <samuel.holland@...ive.com>
Cc:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>, Tom Rix <trix@...hat.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/display: Allow building DC with clang on RISC-V

On Mon, Jul 17, 2023 at 03:29:23PM -0700, Samuel Holland wrote:
> clang on RISC-V appears to be unaffected by the bug causing excessive
> stack usage in calculate_bandwidth(). clang 16 with -fstack-usage
> reports a 304 byte stack frame size with CONFIG_ARCH_RV32I, and 512
> bytes with CONFIG_ARCH_RV64I.
> 
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>

I built ARCH=riscv allmodconfig drivers/gpu/drm/amd/amdgpu/ (confirming
that CONFIG_DRM_AMD_DC gets enabled) with LLVM 11 through 17 with and
without CONFIG_KASAN=y and I never saw the -Wframe-larger-than instance
that this was disabled for, so I agree.

Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Tested-by: Nathan Chancellor <nathan@...nel.org>

> 
>  drivers/gpu/drm/amd/display/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
> index bf0a655d009e..901d1961b739 100644
> --- a/drivers/gpu/drm/amd/display/Kconfig
> +++ b/drivers/gpu/drm/amd/display/Kconfig
> @@ -5,7 +5,7 @@ menu "Display Engine Configuration"
>  config DRM_AMD_DC
>  	bool "AMD DC - Enable new display engine"
>  	default y
> -	depends on BROKEN || !CC_IS_CLANG || X86_64 || SPARC64 || ARM64
> +	depends on BROKEN || !CC_IS_CLANG || ARM64 || RISCV || SPARC64 || X86_64
>  	select SND_HDA_COMPONENT if SND_HDA_CORE
>  	# !CC_IS_CLANG: https://github.com/ClangBuiltLinux/linux/issues/1752
>  	select DRM_AMD_DC_FP if (X86 || LOONGARCH || (PPC64 && ALTIVEC) || (ARM64 && KERNEL_MODE_NEON && !CC_IS_CLANG))
> -- 
> 2.40.1
>