Re: [PATCH v3 08/10] pmdomain: samsung: selectively handle enforced sync_state

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 22.10.2025 13:06, Ulf Hansson wrote:
> On Thu, 16 Oct 2025 at 17:58, André Draszik <andre.draszik@linaro.org> wrote:
>> Unconditionally calling of_genpd_sync_state() causes issues on
>> platforms with child domains as the parent domain will be turned off
>> before the child domain was even registered during boot.
>>
>> This in particular is an issue for the upcoming Google gs101 support -
>> all operations on child domains registered after the parent domain
>> misbehave.
>>
>> Add a flag to the probe data to be able to sync_state conditionally
>> only, and enable that flag on the two platforms currently supported by
>> this driver.
>>
>> Signed-off-by: André Draszik <andre.draszik@linaro.org>
>>
>> ---
>> v2:
>> * use bool for need_early_sync_state (Krzysztof)
>> ---
>>   drivers/pmdomain/samsung/exynos-pm-domains.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/pmdomain/samsung/exynos-pm-domains.c b/drivers/pmdomain/samsung/exynos-pm-domains.c
>> index 638d286b57f716140b2401092415644a6805870e..15a1582aa92103a07335eb681600d9415369fefd 100644
>> --- a/drivers/pmdomain/samsung/exynos-pm-domains.c
>> +++ b/drivers/pmdomain/samsung/exynos-pm-domains.c
>> @@ -20,6 +20,7 @@
>>   struct exynos_pm_domain_config {
>>          /* Value for LOCAL_PWR_CFG and STATUS fields for each domain */
>>          u32 local_pwr_cfg;
>> +       bool need_early_sync_state;
>>   };
>>
>>   /*
>> @@ -69,10 +70,12 @@ static int exynos_pd_power_off(struct generic_pm_domain *domain)
>>
>>   static const struct exynos_pm_domain_config exynos4210_cfg = {
>>          .local_pwr_cfg          = 0x7,
>> +       .need_early_sync_state  = true,
>>   };
>>
>>   static const struct exynos_pm_domain_config exynos5433_cfg = {
>>          .local_pwr_cfg          = 0xf,
>> +       .need_early_sync_state  = true,
>>   };
>>
>>   static const struct of_device_id exynos_pm_domain_of_match[] = {
>> @@ -179,7 +182,7 @@ static int exynos_pd_probe(struct platform_device *pdev)
>>           * reset during boot. As a temporary hack to manage this, let's enforce
>>           * a sync_state.
>>           */
>> -       if (!ret)
>> +       if (pm_domain_cfg->need_early_sync_state && !ret)
>>                  of_genpd_sync_state(np);
> The call to of_genpd_sync_state() was intended as a temporary solution here.
>
> Potentially, if we would be able to distinguish what PM domain that is
> causing the problem on the Exynos platforms, we could set
> GENPD_FLAG_NO_STAY_ON for that genpd instead.

Well, this of_genpd_sync_state() "workaround" has to be applied only to 
the power domain of the display controller device. It can be replaced by 
the following check on the legacy Exynos systems:

if (IS_ENABLED(CONFIG_ARM) &&
of_device_is_compatible(np, "samsung,exynos4210-pd") && 
(strstr(pd->pd.name, "LCD") || strstr(pd->pd.name, "DISP"))) 
pd->pd.flags = GENPD_FLAG_NO_STAY_ON;

I assume that this information cannot be coded in device tree to make it 
somehow generic...

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland