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 <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Tzung-Bi Shih

drivers/gpu/drm/amd/display/dc/dml2/display_mode_core.c

@@ -1736,7 +1736,7 @@ static void CalculateBytePerPixelAndBlockSizes(
 #endif
 } // CalculateBytePerPixelAndBlockSizes
 
-static dml_float_t CalculateTWait(
+static noinline_for_stack dml_float_t CalculateTWait(
 		dml_uint_t PrefetchMode,
 		enum dml_use_mall_for_pstate_change_mode UseMALLForPStateChange,
 		dml_bool_t SynchronizeDRRDisplaysForUCLKPStateChangeFinal,
@@ -4458,7 +4458,7 @@ static void CalculateSwathWidth(
 	}
 } // CalculateSwathWidth
 
-static  dml_float_t CalculateExtraLatency(
+static noinline_for_stack dml_float_t CalculateExtraLatency(
 		dml_uint_t RoundTripPingLatencyCycles,
 		dml_uint_t ReorderingBytes,
 		dml_float_t DCFCLK,
@@ -5915,7 +5915,7 @@ static dml_uint_t DSCDelayRequirement(
 	return DSCDelayRequirement_val;
 }
 
-static dml_bool_t CalculateVActiveBandwithSupport(dml_uint_t NumberOfActiveSurfaces,
+static noinline_for_stack dml_bool_t CalculateVActiveBandwithSupport(dml_uint_t NumberOfActiveSurfaces,
 										dml_float_t ReturnBW,
 										dml_bool_t NotUrgentLatencyHiding[],
 										dml_float_t ReadBandwidthLuma[],
@@ -6019,7 +6019,7 @@ static void CalculatePrefetchBandwithSupport(
 #endif
 }
 
-static dml_float_t CalculateBandwidthAvailableForImmediateFlip(
+static noinline_for_stack dml_float_t CalculateBandwidthAvailableForImmediateFlip(
 													dml_uint_t NumberOfActiveSurfaces,
 													dml_float_t ReturnBW,
 													dml_float_t ReadBandwidthLuma[],
@@ -6213,7 +6213,7 @@ static dml_uint_t CalculateMaxVStartup(
 	return max_vstartup_lines;
 }
 
-static void set_calculate_prefetch_schedule_params(struct display_mode_lib_st *mode_lib,
+static noinline_for_stack void set_calculate_prefetch_schedule_params(struct display_mode_lib_st *mode_lib,
 						   struct CalculatePrefetchSchedule_params_st *CalculatePrefetchSchedule_params,
 						   dml_uint_t j,
 						   dml_uint_t k)
@@ -6265,7 +6265,7 @@ static void set_calculate_prefetch_schedule_params(struct display_mode_lib_st *m
 				CalculatePrefetchSchedule_params->Tno_bw = &mode_lib->ms.Tno_bw[k];
 }
 
-static void dml_prefetch_check(struct display_mode_lib_st *mode_lib)
+static noinline_for_stack void dml_prefetch_check(struct display_mode_lib_st *mode_lib)
 {
 	struct dml_core_mode_support_locals_st *s = &mode_lib->scratch.dml_core_mode_support_locals;
 	struct CalculatePrefetchSchedule_params_st *CalculatePrefetchSchedule_params = &mode_lib->scratch.CalculatePrefetchSchedule_params;

drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c

@@ -2778,7 +2778,7 @@ static double dml_get_return_bandwidth_available(
 	return return_bw_mbps;
 }
 
-static void calculate_bandwidth_available(
+static noinline_for_stack void calculate_bandwidth_available(
 	double avg_bandwidth_available_min[dml2_core_internal_soc_state_max],
 	double avg_bandwidth_available[dml2_core_internal_soc_state_max][dml2_core_internal_bw_max],
 	double urg_bandwidth_available_min[dml2_core_internal_soc_state_max], // min between SDP and DRAM
@@ -3625,7 +3625,7 @@ static void CalculateDCFCLKDeepSleepTdlut(
 	dml2_printf("DML::%s: DCFClkDeepSleep = %f (final)\n", __func__, *DCFClkDeepSleep);
 }
 
-static void CalculateDCFCLKDeepSleep(
+static noinline_for_stack void CalculateDCFCLKDeepSleep(
 	const struct dml2_display_cfg *display_cfg,
 	unsigned int NumberOfActiveSurfaces,
 	unsigned int BytePerPixelY[],
@@ -4142,7 +4142,7 @@ static bool ValidateODMMode(enum dml2_odm_mode ODMMode,
 	return true;
 }
 
-static void CalculateODMMode(
+static noinline_for_stack void CalculateODMMode(
 	unsigned int MaximumPixelsPerLinePerDSCUnit,
 	unsigned int HActive,
 	enum dml2_output_format_class OutFormat,
@@ -4239,7 +4239,7 @@ static void CalculateODMMode(
 #endif
 }
 
-static void CalculateOutputLink(
+static noinline_for_stack void CalculateOutputLink(
 	struct dml2_core_internal_scratch *s,
 	double PHYCLK,
 	double PHYCLKD18,
@@ -5999,7 +5999,7 @@ static double calculate_impacted_Tsw(unsigned int exclude_plane_idx, unsigned in
 }
 
 // a global check against the aggregate effect of the per plane prefetch schedule
-static bool CheckGlobalPrefetchAdmissibility(struct dml2_core_internal_scratch *scratch,
+static noinline_for_stack bool CheckGlobalPrefetchAdmissibility(struct dml2_core_internal_scratch *scratch,
 											 struct dml2_core_calcs_CheckGlobalPrefetchAdmissibility_params *p)
 {
 	struct dml2_core_calcs_CheckGlobalPrefetchAdmissibility_locals *s = &scratch->CheckGlobalPrefetchAdmissibility_locals;
@@ -7012,7 +7012,7 @@ static void calculate_bytes_to_fetch_required_to_hide_latency(
 	}
 }
 
-static void calculate_vactive_det_fill_latency(
+static noinline_for_stack void calculate_vactive_det_fill_latency(
 		const struct dml2_display_cfg *display_cfg,
 		unsigned int num_active_planes,
 		unsigned int bytes_required_l[],