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

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

[Christian Marangi]

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 <sudeep.holla@arm.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501201840.XmpHXpQ4-lkp@intel.com/
Fixes: 82e703dd438b ("pmdomain: airoha: Add Airoha CPU PM Domain support")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/pmdomain/mediatek/Makefile | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pmdomain/mediatek/Makefile b/drivers/pmdomain/mediatek/Makefile
index 0f6edce9239b..18ba92e3c418 100644
--- a/drivers/pmdomain/mediatek/Makefile
+++ b/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
-- 
2.47.1

Re: [PATCH] pmdomain: airoha: Fix compilation error with Clang-20 and Thumb2 mode

[Ulf Hansson]

On Mon, 20 Jan 2025 at 16:38, Christian Marangi <ansuelsmth@gmail.com> wrote:
>
> 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 <sudeep.holla@arm.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202501201840.XmpHXpQ4-lkp@intel.com/
> Fixes: 82e703dd438b ("pmdomain: airoha: Add Airoha CPU PM Domain support")
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

Applied for next, thanks!

Kind regards
Uffe

> ---
>  drivers/pmdomain/mediatek/Makefile | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pmdomain/mediatek/Makefile b/drivers/pmdomain/mediatek/Makefile
> index 0f6edce9239b..18ba92e3c418 100644
> --- a/drivers/pmdomain/mediatek/Makefile
> +++ b/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
> --
> 2.47.1
>