pmdomain: airoha: Fix compilation error with Clang-20 and Thumb2 mode

The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame
pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling
hooks are inserted via the -pg switch.

This is a known issue and similar driver workaround this with a Makefile
ifdef. Exact workaround are applied in
drivers/firmware/arm_scmi/transports/Makefile and other similar driver.

Suggested-by: Sudeep Holla <[email protected]>
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Fixes: 82e703d ("pmdomain: airoha: Add Airoha CPU PM Domain support")
Signed-off-by: Christian Marangi <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ulf Hansson <[email protected]>

Author: Ansuel

drivers/pmdomain/mediatek/Makefile

@@ -2,3 +2,10 @@
 obj-$(CONFIG_MTK_SCPSYS)		+= mtk-scpsys.o
 obj-$(CONFIG_MTK_SCPSYS_PM_DOMAINS) 	+= mtk-pm-domains.o
 obj-$(CONFIG_AIROHA_CPU_PM_DOMAIN) 	+= airoha-cpu-pmdomain.o
+
+ifeq ($(CONFIG_THUMB2_KERNEL)$(CONFIG_CC_IS_CLANG),yy)
+# The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame
+# pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling
+# hooks are inserted via the -pg switch.
+CFLAGS_REMOVE_airoha-cpu-pmdomain.o += $(CC_FLAGS_FTRACE)
+endif