Re: [PATCH v2] ARM: EXYNOS: Use MCPM call-backs to support S2R on Exynos5420

[Abhilash Kesavan <kesavan.abhilash@gmail.com>]

Hi Nicolas,

On Tue, Jul 1, 2014 at 9:49 AM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote:
> On Mon, 30 Jun 2014, Abhilash Kesavan wrote:
>
>> Use the MCPM layer to handle core suspend/resume on Exynos5420.
>> Also, restore the entry address setup code post-resume.
>>
>> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
>> ---
> [...]
>
> Could you tell me more about this?
>
>> @@ -150,7 +153,13 @@ static void exynos_power_down(void)
>>       BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
>>       cpu_use_count[cpu][cluster]--;
>>       if (cpu_use_count[cpu][cluster] == 0) {
>> -             exynos_cpu_power_down(cpunr);
>> +             /*
>> +              * Bypass power down for CPU0 during suspend. This is being
>> +              * taken care by the SYS_PWR_CFG bit in CORE0_SYS_PWR_REG.
>> +              */
>> +             if ((cpunr != 0) ||
>> +             (__raw_readl(pmu_base_addr + S5P_INFORM1) != S5P_CHECK_SLEEP))
>> +                     exynos_cpu_power_down(cpunr);
>
> What happens if CPU0 is the first in the cluster to be idled?  Will it
> remain powered up until all the others have gone idle too?
This check is only for handling the S2R CPU0 case. In case of
idle/switching the S5P_CHECK_SLEEP flag would not be set and hence
there would be no change in behavior for them.
During suspend, we enable the ARM_USE_STANDBY_WFI0 bit which tells the
PMU when the CPU0 is ready to be suspended. This in conjunction with
the sleep state core configuration (setting SYS_PWR_REG low) causes
the CPU0 to go down. We should not write to the CPU0 power
configuration register (exynos_cpu_power_down) along with this during
suspend.

Regards,
Abhilash
>
>
> Nicolas