Re: [PATCH 0/5] drm/amd/display: Reduce stack usage for clang

[Nathan Chancellor <nathan@kernel.org>]

Hi Rodrigo,

On Mon, Sep 12, 2022 at 05:50:31PM -0400, Rodrigo Siqueira Jordao wrote:
> 
> 
> On 2022-08-30 16:34, Nathan Chancellor wrote:
> > Hi all,
> > 
> > This series aims to address the following warnings, which are visible
> > when building x86_64 allmodconfig with clang after commit 3876a8b5e241
> > ("drm/amd/display: Enable building new display engine with KCOV
> > enabled").
> > 
> >      drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn30/display_mode_vba_30.c:3542:6: error: stack frame size (2200) exceeds limit (2048) in 'dml30_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
> >      void dml30_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
> >          ^
> >      1 error generated.
> > 
> >      drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_mode_vba_31.c:3908:6: error: stack frame size (2216) exceeds limit (2048) in 'dml31_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
> >      void dml31_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
> >          ^
> >      1 error generated.
> > 
> >      drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c:1721:6: error: stack frame size (2152) exceeds limit (2048) in 'dml32_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
> >      void dml32_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
> >          ^
> >      1 error generated.
> > 
> > This series is based on commit b3235e8635e1 ("drm/amd/display: clean up
> > some inconsistent indentings"). These warnings are fatal for
> > allmodconfig due to CONFIG_WERROR so ideally, I would like to see these
> > patches cherry-picked to a branch targeting mainline to allow our builds
> > to go back to green. However, since this series is not exactly trivial
> > in size, I can understand not wanting to apply these to mainline during
> > the -rc cycle. If they cannot be cherry-picked to mainline, I can add a
> > patch raising the value of -Wframe-larger-than for these files that can
> > be cherry-picked to 6.0/mainline then add a revert of that change as the
> > last patch in the stack so everything goes back to normal for -next/6.1.
> > I am open to other options though!
> > 
> > I have built this series against clang 16.0.0 (ToT) and GCC 12.2.0 for
> > x86_64. It has seen no runtime testing, as my only test system with AMD
> > graphics is a Renoir one, which as far as I understand it uses DCN 2.1.
> > 
> > Nathan Chancellor (5):
> >    drm/amd/display: Reduce number of arguments of
> >      dml32_CalculateWatermarksMALLUseAndDRAMSpeedChangeSupport()
> >    drm/amd/display: Reduce number of arguments of
> >      dml32_CalculatePrefetchSchedule()
> >    drm/amd/display: Reduce number of arguments of dml31's
> >      CalculateWatermarksAndDRAMSpeedChangeSupport()
> >    drm/amd/display: Reduce number of arguments of dml31's
> >      CalculateFlipSchedule()
> >    drm/amd/display: Mark dml30's UseMinimumDCFCLK() as noinline for stack
> >      usage
> > 
> >   .../dc/dml/dcn30/display_mode_vba_30.c        |   2 +-
> >   .../dc/dml/dcn31/display_mode_vba_31.c        | 420 +++++-------------
> >   .../dc/dml/dcn32/display_mode_vba_32.c        | 236 +++-------
> >   .../dc/dml/dcn32/display_mode_vba_util_32.c   | 323 ++++++--------
> >   .../dc/dml/dcn32/display_mode_vba_util_32.h   |  51 +--
> >   5 files changed, 318 insertions(+), 714 deletions(-)
> > 
> > 
> > base-commit: b3235e8635e1dd7ac1a27a73330e9880dfe05154
> 
> Hi Nathan,
> 
> First of all, thanks a lot for your patchset!
> 
> Sorry for the delay; it took me more time than I expected to review and run
> a couple of tests in this patchset (most of them were IGT). Anyway, I'm good
> with this change; this series is:
> 
> Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> 
> And I applied it to amd-staging-drm-next.
> 
> We will run some extra tests this week; if we find some issues, I'll debug
> them.
> 
> Also, thanks, Maíra, for checking this patch as well.

No worries on the delay, the series is not exactly the smallest one I
have ever sent :) While the changes were mostly mechanical, I could have
definitely messed something up and I appreciate you taking the time to
review it and run it through some tests. Please let me know if I can be
of further assistance on that front.

If you have any thoughts on the blurb I had in the cover letter around
how to handle the warnings this series resolves with regards to
mainline, I would love to hear them.

Cheers,
Nathan