[PATCH 5/5] drm/amd/display: Mark dml30's UseMinimumDCFCLK() as noinline for stack usage

[Nathan Chancellor <nathan@kernel.org>]

This function consumes a lot of stack space and it blows up the size of
dml30_ModeSupportAndSystemConfigurationFull() with clang:

  drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn30/display_mode_vba_30.c:3542:6: error: stack frame size (2200) exceeds limit (2048) in 'dml30_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
  void dml30_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
       ^
  1 error generated.

Commit a0f7e7f759cf ("drm/amd/display: fix i386 frame size warning")
aimed to address this for i386 but it did not help x86_64.

To reduce the amount of stack space that
dml30_ModeSupportAndSystemConfigurationFull() uses, mark
UseMinimumDCFCLK() as noinline, using the _for_stack variant for
documentation. While this will increase the total amount of stack usage
between the two functions (1632 and 1304 bytes respectively), it will
make sure both stay below the limit of 2048 bytes for these files. The
aforementioned change does help reduce UseMinimumDCFCLK()'s stack usage
so it should not be reverted in favor of this change.

Link: https://github.com/ClangBuiltLinux/linux/issues/1681
Reported-by: "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@gmail.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c b/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
index b7fa003ffe06..6991a68061ef 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
@@ -6497,7 +6497,7 @@ static double CalculateUrgentLatency(
 	return ret;
 }
 
-static void UseMinimumDCFCLK(
+static noinline_for_stack void UseMinimumDCFCLK(
 		struct display_mode_lib *mode_lib,
 		struct vba_vars_st *v,
 		int MaxPrefetchMode,
-- 
2.37.2