drm/amd/display: mark static functions noinline_for_stack

When compiling allmodconfig (CONFIG_WERROR=y) with clang-19, see the
following errors:

.../display/dc/dml2/display_mode_core.c:6268:13: warning: stack frame size (3128) exceeds limit (3072) in 'dml_prefetch_check' [-Wframe-larger-than]
.../display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c:7236:13: warning: stack frame size (3256) exceeds limit (3072) in 'dml_core_mode_support' [-Wframe-larger-than]

Mark static functions called by dml_prefetch_check() and
dml_core_mode_support() noinline_for_stack to avoid them become huge
functions and thus exceed the frame size limit.

A way to reproduce:
$ git checkout next-20250107
$ mkdir build_dir
$ export PATH=/tmp/llvm-19.1.6-x86_64/bin:$PATH
$ make LLVM=1 O=build_dir allmodconfig
$ make LLVM=1 O=build_dir drivers/gpu/drm/ -j

The way how it chose static functions to mark:
[0] Unset CONFIG_WERROR in build_dir/.config.
To get display_mode_core.o without errors.

[1] Get a function list called by dml_prefetch_check().
$ sed -n '6268,6711p' drivers/gpu/drm/amd/display/dc/dml2/display_mode_core.c \
  | sed -n -r 's/.*\W(\w+)\(.*/\1/p' | sort -u >/tmp/syms

[2] Get the non-inline function list.
Objdump won't show the symbols if they are inline functions.

$ make LLVM=1 O=build_dir drivers/gpu/drm/ -j
$ objdump -d build_dir/.../display_mode_core.o | \
  ./scripts/checkstack.pl x86_64 0 | \
  grep -f /tmp/syms | cut -d' ' -f2- >/tmp/orig

[3] Get the full function list.
Append "-fno-inline" to `CFLAGS_.../display_mode_core.o` in
drivers/gpu/drm/amd/display/dc/dml2/Makefile.

$ make LLVM=1 O=build_dir drivers/gpu/drm/ -j
$ objdump -d build_dir/.../display_mode_core.o | \
  ./scripts/checkstack.pl x86_64 0 | \
  grep -f /tmp/syms | cut -d' ' -f2- >/tmp/noinline

[4] Get the inline function list.
If a symbol only in /tmp/noinline but not in /tmp/orig, it is a good
candidate to mark noinline.

$ diff /tmp/orig /tmp/noinline

Chosen functions and their stack sizes:
CalculateBandwidthAvailableForImmediateFlip [display_mode_core.o]:144
CalculateExtraLatency [display_mode_core.o]:176
CalculateTWait [display_mode_core.o]:64
CalculateVActiveBandwithSupport [display_mode_core.o]:112
set_calculate_prefetch_schedule_params [display_mode_core.o]:48

CheckGlobalPrefetchAdmissibility [dml2_core_dcn4_calcs.o]:544
calculate_bandwidth_available [dml2_core_dcn4_calcs.o]:320
calculate_vactive_det_fill_latency [dml2_core_dcn4_calcs.o]:272
CalculateDCFCLKDeepSleep [dml2_core_dcn4_calcs.o]:208
CalculateODMMode [dml2_core_dcn4_calcs.o]:208
CalculateOutputLink [dml2_core_dcn4_calcs.o]:176

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions