linux-kernel - Re: [PATCH 3/3] drm/amd/display: Support DRM_AMD_DC

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Date:   Wed, 29 Nov 2023 17:42:24 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     Samuel Holland <samuel.holland@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...il.com>,
        Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Pan Xinhui <Xinhui.Pan@....com>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        llvm@...ts.linux.dev, arnd@...db.de
Subject: Re: [PATCH 3/3] drm/amd/display: Support DRM_AMD_DC_FP on RISC-V

On Thu, Nov 23, 2023 at 02:23:01PM +0000, Conor Dooley wrote:
> On Tue, Nov 21, 2023 at 07:05:15PM -0800, Samuel Holland wrote:
> > RISC-V uses kernel_fpu_begin()/kernel_fpu_end() like several other
> > architectures. Enabling hardware FP requires overriding the ISA string
> > for the relevant compilation units.
> 
> Ah yes, bringing the joy of frame-larger-than warnings to RISC-V:
> ../drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c:58:13: warning: stack frame size (2416) exceeds limit (2048) in 'DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndPerformanceCalculation' [-Wframe-larger-than]

:(

> Nathan, have you given up on these being sorted out?

Does your configuration have KASAN (I don't think RISC-V supports
KCSAN)? It is possible that dml/dcn32 needs something similar to commit
6740ec97bcdb ("drm/amd/display: Increase frame warning limit with KASAN
or KCSAN in dml2")?

I am not really interested in playing whack-a-mole with these warnings
like I have done in the past for the reasons I outlined here:

https://lore.kernel.org/20231019205117.GA839902@dev-arch.thelio-3990X/

> Also, what on earth is that function name, it exceeds 80 characters
> before even considering anything else? Actually, I don't think I want
> to know.

Welcome to "gcc-parsable HW gospel, coming straight from HW engineers" :)

Cheers,
Nathan