drm/amd/display: Respect user's CONFIG_FRAME_WARN more for dml files

Currently, there are several files in drm/amd/display that aim to have a
higher -Wframe-larger-than value to avoid instances of that warning with
a lower value from the user's configuration. However, with the way that
it is currently implemented, it does not respect the user's request via
CONFIG_FRAME_WARN for a higher stack frame limit, which can cause pain
when new instances of the warning appear and break the build due to
CONFIG_WERROR.

Adjust the logic to switch from a hard coded -Wframe-larger-than value
to only using the value as a minimum clamp and deferring to the
requested value from CONFIG_FRAME_WARN if it is higher.

Suggested-by: Harry Wentland <[e-mail]>
Reported-by: Greg Kroah-Hartman <[e-mail]>
Closes: https://lore.kernel.org/2025013003-audience-opposing-7f95@gregkh/
Signed-off-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dml/Makefile

···
 dml_rcflags := $(CC_FLAGS_NO_FPU)
 
 ifneq ($(CONFIG_FRAME_WARN),0)
-ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)
-frame_warn_flag := -Wframe-larger-than=3072
-else
-frame_warn_flag := -Wframe-larger-than=2048
-endif
+    ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)
+        frame_warn_limit := 3072
+    else
+        frame_warn_limit := 2048
+    endif
+
+    ifeq ($(call test-lt, $(CONFIG_FRAME_WARN), $(frame_warn_limit)),y)
+        frame_warn_flag := -Wframe-larger-than=$(frame_warn_limit)
+    endif
 endif
 
 CFLAGS_$(AMDDALPATH)/dc/dml/display_mode_lib.o := $(dml_ccflags)

drivers/gpu/drm/amd/display/dc/dml2/Makefile

···
 dml2_rcflags := $(CC_FLAGS_NO_FPU)
 
 ifneq ($(CONFIG_FRAME_WARN),0)
-ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)
-ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_COMPILE_TEST),yy)
-frame_warn_flag := -Wframe-larger-than=4096
-else
-frame_warn_flag := -Wframe-larger-than=3072
-endif
-else
-frame_warn_flag := -Wframe-larger-than=2048
-endif
+    ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)
+        ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_COMPILE_TEST),yy)
+            frame_warn_limit := 4096
+        else
+            frame_warn_limit := 3072
+        endif
+    else
+        frame_warn_limit := 2048
+    endif
+
+    ifeq ($(call test-lt, $(CONFIG_FRAME_WARN), $(frame_warn_limit)),y)
+        frame_warn_flag := -Wframe-larger-than=$(frame_warn_limit)
+    endif
 endif
 
 subdir-ccflags-y += -I$(FULL_AMD_DISPLAY_PATH)/dc/dml2