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

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Message-ID: <CAPDyKFpBtnsEfMg73UHdXzZvSNHaL8H4N1h6-2wAMnFWNTM75w@mail.gmail.com>
Date: Tue, 21 Jan 2025 10:46:11 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, llvm@...ts.linux.dev, 
	Sudeep Holla <sudeep.holla@....com>, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] pmdomain: airoha: Fix compilation error with Clang-20 and
 Thumb2 mode

On Mon, 20 Jan 2025 at 16:38, Christian Marangi <ansuelsmth@...il.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@....com>
> Reported-by: kernel test robot <lkp@...el.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@...il.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
>