Re: [PATCH v4 1/5] arm: psci: Add API to check for support of specific PSCI function

[Casey Connolly]

On 13/06/2025 07:19, Varadarajan Narayanan wrote:
> Add an API to check if a specific PSCI function is supported or not.
> This is based on the psci_features() function present in Linux kernel
> (drivers/firmware/psci/psci.c).
> 
> Signed-off-by: Varadarajan Narayanan <quic_var...@quicinc.com>

Reviewed-by: Casey Connolly <casey.conno...@linaro.org>

> ---
>  arch/arm/cpu/armv8/fwcall.c   | 15 +++++++++++++++
>  arch/arm/include/asm/system.h |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/arch/arm/cpu/armv8/fwcall.c b/arch/arm/cpu/armv8/fwcall.c
> index 87de09979b1..f834d770dd6 100644
> --- a/arch/arm/cpu/armv8/fwcall.c
> +++ b/arch/arm/cpu/armv8/fwcall.c
> @@ -129,3 +129,18 @@ void __noreturn psci_system_off(void)
>       while (1)
>               ;
>  }
> +
> +int psci_features(u32 psci_func_id)
> +{
> +     struct pt_regs regs;
> +
> +     regs.regs[0] = ARM_PSCI_1_0_FN_PSCI_FEATURES;
> +     regs.regs[1] = psci_func_id;
> +
> +     if (use_smc_for_psci)
> +             smc_call(&regs);
> +     else
> +             hvc_call(&regs);
> +
> +     return regs.regs[0];
> +}
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 4c1b81483c9..0b788bcf0e5 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -336,6 +336,7 @@ void smc_call(struct pt_regs *args);
>  void __noreturn psci_system_reset(void);
>  void __noreturn psci_system_reset2(u32 reset_level, u32 cookie);
>  void __noreturn psci_system_off(void);
> +int psci_features(u32 psci_func_id);
>  
>  #ifdef CONFIG_ARMV8_PSCI
>  extern char __secure_start[];

-- 
// Casey (she/her)