Re: Stack-frame warnings in display_mode_vba_32.c

From: Paul E. McKenney
Date: Sat Jul 30 2022 - 01:12:47 EST


On Fri, Jul 29, 2022 at 11:41:55PM -0300, André Almeida wrote:
> Hi Paul,
>
> Às 23:25 de 29/07/22, Paul E. McKenney escreveu:
> > Hello!
> >
> > I am seeing the following in allmodconfig builds of recent -next on x86:
> >
> > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c: In function ‘DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndPerformanceCalculation’:
> > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c:1659:1: error: the frame size of 2144 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
> > 1659 | }
> > | ^
> > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c: In function ‘dml32_ModeSupportAndSystemConfigurationFull’:
> > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/display_mode_vba_32.c:3799:1: error: the frame size of 2480 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
> > 3799 | } // ModeSupportAndSystemConfigurationFull
> > | ^
>
> I think they are fixed at amd-staging-drm-next:
>
> git log --oneline amd/amd-staging-drm-next
> drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c
> 953daa61981b drm/amd/display: Reduce stack size in the mode support function
> 361e705e712d drm/amd/display: reduce stack for
> dml32_CalculatePrefetchSchedule
> f2dbf5a4dd1e drm/amd/display: reduce stack for
> dml32_CalculateWatermarksMALLUseAndDRAMSpeedChangeSupport
> a0a68cda2ef8 drm/amd/display: reduce stack for dml32_CalculateVMRowAndSwath
> ca6730ca0f01 drm/amd/display: reduce stack for
> dml32_CalculateSwathAndDETConfiguration
> 593eef8c1a5e drm/amd/display: reduce stack size in dcn32 dml (v2)
>
> https://gitlab.freedesktop.org/agd5f/linux/-/commits/amd-staging-drm-next/drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_32.c

Very good, thank you! I will test again on the next -next.

Thanx, Paul

> > Bisection located the commit shown below. Doing an allmodconfig build
> > on this commit reproduces the error, its parent builds fine.
> >
> > Thoughts?
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit 3876a8b5e241081b2a519f848a65c00d8e6cd124
> > Author: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Date: Tue Jul 12 15:42:47 2022 -0700
> >
> > drm/amd/display: Enable building new display engine with KCOV enabled
> >
> > The new display engine uses floating point math, which is not supported
> > by KCOV. Commit 9d1d02ff3678 ("drm/amd/display: Don't build DCN1 when kcov
> > is enabled") tried to work around the problem by disabling
> > CONFIG_DRM_AMD_DC_DCN if KCOV_INSTRUMENT_ALL and KCOV_ENABLE_COMPARISONS
> > are enabled. The result is that KCOV can not be enabled on systems which
> > require this display engine. A much simpler and less invasive solution is
> > to disable KCOV selectively when compiling the display enagine while
> > keeping it enabled for the rest of the kernel.
> >
> > Fixes: 9d1d02ff3678 ("drm/amd/display: Don't build DCN1 when kcov is enabled")
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Leo Li <sunpeng.li@xxxxxxx>
> > Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> >
> > diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
> > index b4029c0d5d8c5..96cbc87f7b6b8 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) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
> > + select DRM_AMD_DC_DCN if (X86 || PPC64)
> > help
> > Choose this option if you want to use the new display engine
> > support for AMDGPU. This adds required support for Vega and
> > diff --git a/drivers/gpu/drm/amd/display/dc/Makefile b/drivers/gpu/drm/amd/display/dc/Makefile
> > index 273f8f2c8e020..b9effadfc4bb7 100644
> > --- a/drivers/gpu/drm/amd/display/dc/Makefile
> > +++ b/drivers/gpu/drm/amd/display/dc/Makefile
> > @@ -25,6 +25,9 @@
> > DC_LIBS = basics bios dml clk_mgr dce gpio irq link virtual
> >
> > ifdef CONFIG_DRM_AMD_DC_DCN
> > +
> > +KCOV_INSTRUMENT := n
> > +
> > DC_LIBS += dcn20
> > DC_LIBS += dsc
> > DC_LIBS += dcn10