Re: Stack-frame warnings in display_mode_vba_32.c

["André Almeida" <andrealmeid@igalia.com>]

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

> 
> 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@roeck-us.net>
> 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@arndb.de>
>     Cc: Leo Li <sunpeng.li@amd.com>
>     Reviewed-by: Harry Wentland <harry.wentland@amd.com>
>     Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>     Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> 
> 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