Re: [PATCH] drm/amdgpu: make DRM_AMD_DC x86-only again

["Christian König" <christian.koenig@amd.com>]

Am 07.12.20 um 21:47 schrieb Alex Deucher:
> On Fri, Dec 4, 2020 at 3:13 AM Arnd Bergmann <arnd@kernel.org> wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>>
>> As the DRM_AMD_DC_DCN3_0 code was x86-only and fails to build on
>> arm64, merging it into DRM_AMD_DC means that the top-level symbol
>> is now x86-only as well.
>>
>> Compilation fails on arm64 with clang-12 with
>>
>> drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn30/display_mode_vba_30.c:3641:6: error: stack frame size of 2416 bytes in function 'dml30_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than=]
>> void dml30_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
>>
>> I tried to see if the stack usage can be reduced, but this is code
>> that is described as "This file is gcc-parsable HW gospel, coming
>> straight from HW engineers." and is written in a way that is inherently
>> nonportable and not meant to be understood by humans.
>>
>> There are probably no non-x86 users of this code, so simplify
>> the dependency list accordingly.
> + Daniel, Timothy
>
> Others contributed code to enable this on PPC64 and ARM64.
> Unfortunately, we don't have these platforms to test with within AMD.
> Does PPC64 have the same stack limitations as ARM64?  Harry, Leo, can
> you take a look at fixing the stack usage?

This reminds me that I wanted to reply on this.

2416 is even to much on x86 if you add -Werror :)

So this needs to be fixed anyway.

Christian.

>
> Thanks,
>
> Alex
>
>> Fixes: 20f2ffe50472 ("drm/amdgpu: fold CONFIG_DRM_AMD_DC_DCN3* into CONFIG_DRM_AMD_DC_DCN (v3)")
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>   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 797b5d4b43e5..54aa50d4deba 100644
>> --- a/drivers/gpu/drm/amd/display/Kconfig
>> +++ b/drivers/gpu/drm/amd/display/Kconfig
>> @@ -6,7 +6,7 @@ config DRM_AMD_DC
>>          bool "AMD DC - Enable new display engine"
>>          default y
>>          select SND_HDA_COMPONENT if SND_HDA_CORE
>> -       select DRM_AMD_DC_DCN if (X86 || PPC64 || (ARM64 && KERNEL_MODE_NEON)) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
>> +       select DRM_AMD_DC_DCN if X86 && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
>>          help
>>            Choose this option if you want to use the new display engine
>>            support for AMDGPU. This adds required support for Vega and
>> --
>> 2.27.0
>>
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