[PATCH] ARM: stm32: Jump to ep on successful resume in PSCI suspend code

[Patrice CHOTARD]

On 3/31/24 20:21, Marek Vasut wrote:
> In case the system has resumed successfully, the PSCI suspend resume
> code has to jump to the 'ep' successful resume entry point code path,
> otherwise the code has to jump to content of the LR register, which
> points to failed resume code path.
> 
> To implement this distinction, rewrite LR register stored on stack
> with 'ep' value in case of a successful resume, which is really in
> every case unless some catastrophic failure occurred during suspend.
> 
> Without this change, Linux counts every resume as failed in
> /sys/power/suspend_stats/fail
> 
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
> Cc: Patrice Chotard <patrice.chotard at foss.st.com>
> Cc: Patrick Delaunay <patrick.delaunay at foss.st.com>
> Cc: u-boot at dh-electronics.com
> Cc: u-boot at lists.denx.de
> Cc: uboot-stm32 at st-md-mailman.stormreply.com
> ---
>  arch/arm/mach-stm32mp/psci.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/arch/arm/mach-stm32mp/psci.c b/arch/arm/mach-stm32mp/psci.c
> index 8cdeb0ab3f2..4f2379df45f 100644
> --- a/arch/arm/mach-stm32mp/psci.c
> +++ b/arch/arm/mach-stm32mp/psci.c
> @@ -703,6 +703,8 @@ void __secure psci_system_suspend(u32 __always_unused function_id,
>  {
>  	u32 saved_mcudivr, saved_pll3cr, saved_pll4cr, saved_mssckselr;
>  	u32 gicd_addr = stm32mp_get_gicd_base_address();
> +	u32 cpu = psci_get_cpu_id();
> +	u32 sp = (u32)__secure_stack_end - (cpu << ARM_PSCI_STACK_SHIFT);
>  	bool iwdg1_wake = false;
>  	bool iwdg2_wake = false;
>  	bool other_wake = false;
> @@ -805,4 +807,16 @@ void __secure psci_system_suspend(u32 __always_unused function_id,
>  
>  	writel(SYSCFG_CMPENR_MPUEN, STM32_SYSCFG_BASE + SYSCFG_CMPENSETR);
>  	clrbits_le32(STM32_SYSCFG_BASE + SYSCFG_CMPCR, SYSCFG_CMPCR_SW_CTRL);
> +
> +	/*
> +	 * The system has resumed successfully. Rewrite LR register stored
> +	 * on stack with 'ep' value, so that on return from this PSCI call,
> +	 * the code would jump to that 'ep' resume entry point code path
> +	 * instead of the previous 'lr' register content which (e.g. with
> +	 * Linux) points to resume failure code path.
> +	 *
> +	 * See arch/arm/cpu/armv7/psci.S _smc_psci: for the stack layout
> +	 * used here, SP-4 is PC, SP-8 is LR, SP-12 is R7, and so on.
> +	 */
> +	writel(ep, sp - 8);
>  }

Hi Marek

This patch is not based on last next or master branch, psci.c is now located in 
arch/arm/mach-stm32mp/stm32mp1/psci.c 

Nevertheless, you can add my RB on the V2.

Thanks
Patrice