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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 7 Dec 2020 14:07:53 -0800
Message-ID: <CAKwvOd=-2zoc06EY4R9ZJ0M874bQv3NuT8a0q9=RoYeMMtnXVQ@mail.gmail.com>
Subject: Re: [PATCH] drm/amdgpu: make DRM_AMD_DC x86-only again
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Alex Deucher <alexdeucher@gmail.com>,
        Harry Wentland <harry.wentland@amd.com>,
        Leo Li <sunpeng.li@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Luben Tuikov <luben.tuikov@amd.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Mauro Rossi <issor.oruam@gmail.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Roman Li <Roman.Li@amd.com>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>,
        Daniel Kolesa <daniel@octaforge.org>,
        Timothy Pearson <tpearson@raptorengineering.com>
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On Mon, Dec 7, 2020 at 1:57 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Mon, Dec 7, 2020 at 9:50 PM Christian K=C3=B6nig <christian.koenig@amd=
.com> wrote:
> > 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_ModeS=
upportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than=3D]
> > >> 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 inheren=
tly
> > >> 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.
>
> Right, looking at my latest randconfig logs, I see the same problem on x8=
6
> builds with clang as well, though I'm not entirely sure which other
> configuration
> options are needed to trigger it.
>
> So my patch can be disregarded, but I agree this needs a better fix,
> either in clang or in the dcn driver.

If you could give https://github.com/ClangBuiltLinux/frame-larger-than
a spin again, I would appreciate any feedback.


--=20
Thanks,
~Nick Desaulniers