[PATCH] ARM: stm32: Add IWDG handling into PSCI suspend code

[Marek Vasut]

On 5/11/23 08:39, Patrice CHOTARD wrote:

Hi,

> On 5/11/23 02:22, Marek Vasut wrote:
>> In case the IWDG is enabled by either U-Boot or Linux, the IWDG can never
>> be disabled again. That includes low power states, which means that if the
>> IWDG is enabled, the SoC would reset itself after a while in suspend via
>> the IWDG. This is not desired behavior.
>>
>> It is possible to enable IWDG pre-timeout IRQ which is routed into the EXTI,
>> and use that IRQ to wake the CPU up before the IWDG timeout is reached and
>> reset is triggered. This pre-timeout IRQ can be used to reload the WDT and
>> then suspend the CPU again every once in a while.
>>
>> Implement this functionality for both IWDG1 and IWDG2 by reading out all
>> the unmasked IRQs, comparing the list with currently pending IRQs in GICv3:
>> - If any IRQ is pending and it is NOT IWDG1 or IWDG2 pre-timeout IRQ,
>>    wake up and let OS handle the IRQs
>> - If IWDG1 or IWDG2 IRQ is pending and no other IRQ is pending,
>>    ping the respective IWDG and suspend again
>>
>> This does not seem to have any adverse impact on power consumption in suspend.

[...]

>> +		/* Ping IWDG2 and ACK pretimer IRQ */
>> +		if (iwdg2_wake) {
>> +			writel(IWDG_KR_RELOAD_KEY, STM32_IWDG2_BASE + IWDG_KR);
>> +			writel(IWDG_EWCR_EWIC, STM32_IWDG2_BASE + IWDG_EWCR);
>> +		}
>> +	}
>>   
>>   	writel(0x3, STM32_RCC_BASE + RCC_MP_SREQCLRR);
>>   	ddr_sw_self_refresh_exit();
> 
> 
> Reviewed-by: Patrice Chotard <patrice.chotard at foss.st.com>

I feel like maybe I need to whack the IWDG also BEFORE entering suspend, 
expect a V2 shortly.

Do you think this IWDG approach is fine to keep the system from 
rebooting in suspend ? Or do you see any better option for the MP1 ?