linux-kernel - Re: [PATCH 0/4] Fix stack usage of DML

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Date:   Thu, 9 Sep 2021 14:53:31 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Harry Wentland <harry.wentland@....com>
Cc:     amd-gfx@...ts.freedesktop.org, ndesaulniers@...gle.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        arnd@...nel.org, sunpeng.li@....com, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com, linux@...ck-us.net,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 0/4] Fix stack usage of DML

On Wed, Sep 08, 2021 at 09:00:19PM -0400, Harry Wentland wrote:
> With the '-Werror' enablement patch the amdgpu build was failing
> on clang builds because a bunch of functions were blowing past
> the 1024 byte stack frame default. Due to this we also noticed
> that a lot of functions were passing large structs by value
> instead of by pointer.
> 
> This series attempts to fix this.
> 
> There is still one remaining function that blows the 1024 limit by 40 bytes:
> 
> drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn21/display_mode_vba_21.c:3397:6:
>  
> error: stack frame size of 1064 bytes in function 
> 'dml21_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than=]
> 
> This will be a slightly more challenging fix but I'll see if we can get it
> below 1024 by breaking it into smaller functions.
> 
> With this series I can build amdgpu with CC=clang and a stack frame limit of 
> 1064.
> 
> This series boots on a Radeon RX 5500 XT.
> 
> Harry Wentland (4):
>   drm/amd/display: Pass display_pipe_params_st as const in DML
>   drm/amd/display: Pass all structs in display_rq_dlg_helpers by pointer
>   drm/amd/display: Fix rest of pass-by-value structs in DML
>   drm/amd/display: Allocate structs needed by dcn_bw_calc_rq_dlg_ttu in
>     pipe_ctx

This series resolves some warnings that were reported on our issue
tracker for 32-bit x86. I do see some other warnings in amdgpu with
clang in various configurations but this is a great start. Thank you for
taking a look at them. For the series:

Build-tested-by: Nathan Chancellor <nathan@...nel.org>

>  .../gpu/drm/amd/display/dc/calcs/dcn_calcs.c  |  55 ++--
>  .../drm/amd/display/dc/dcn20/dcn20_resource.c |   2 +-
>  .../dc/dml/dcn20/display_rq_dlg_calc_20.c     | 158 +++++------
>  .../dc/dml/dcn20/display_rq_dlg_calc_20.h     |   4 +-
>  .../dc/dml/dcn20/display_rq_dlg_calc_20v2.c   | 156 +++++------
>  .../dc/dml/dcn20/display_rq_dlg_calc_20v2.h   |   4 +-
>  .../dc/dml/dcn21/display_rq_dlg_calc_21.c     | 156 +++++------
>  .../dc/dml/dcn21/display_rq_dlg_calc_21.h     |   4 +-
>  .../dc/dml/dcn30/display_rq_dlg_calc_30.c     | 132 ++++-----
>  .../dc/dml/dcn30/display_rq_dlg_calc_30.h     |   4 +-
>  .../dc/dml/dcn31/display_rq_dlg_calc_31.c     | 166 ++++++------
>  .../dc/dml/dcn31/display_rq_dlg_calc_31.h     |   4 +-
>  .../drm/amd/display/dc/dml/display_mode_lib.h |   4 +-
>  .../display/dc/dml/display_rq_dlg_helpers.c   | 256 +++++++++---------
>  .../display/dc/dml/display_rq_dlg_helpers.h   |  20 +-
>  .../display/dc/dml/dml1_display_rq_dlg_calc.c | 246 ++++++++---------
>  .../display/dc/dml/dml1_display_rq_dlg_calc.h |  10 +-
>  .../gpu/drm/amd/display/dc/inc/core_types.h   |   3 +
>  18 files changed, 695 insertions(+), 689 deletions(-)
> 
> -- 
> 2.33.0