Stack-frame warnings in display_mode_vba_32.c

From: Paul E. McKenney
Date: Fri Jul 29 2022 - 22:25:42 EST


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
| ^

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