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SubjectRe: [PATCH v8 08/26] PM / Domains: Extend genpd CPU governor to cope with QoS constraints
On 19 July 2018 at 12:35, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Wednesday, June 20, 2018 7:22:08 PM CEST Ulf Hansson wrote:
>> CPU devices and other regular devices may share the same PM domain and may
>> also be hierarchically related via subdomains. In either case, all devices
>> including CPUs, may be attached to a PM domain managed by genpd, that has
>> an idle state with an enter/exit latency.
>>
>> Let's take these latencies into account in the state selection process by
>> genpd's governor for CPUs. This means the governor, pm_domain_cpu_gov,
>> becomes extended to satisfy both a state's residency and a potential dev PM
>> QoS constraint.
>>
>> Cc: Lina Iyer <ilina@codeaurora.org>
>> Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>> ---
>> drivers/base/power/domain_governor.c | 15 +++++++++++----
>> include/linux/pm_domain.h | 1 +
>> 2 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/base/power/domain_governor.c b/drivers/base/power/domain_governor.c
>> index 1aad55719537..03d4e9454ce9 100644
>> --- a/drivers/base/power/domain_governor.c
>> +++ b/drivers/base/power/domain_governor.c
>> @@ -214,8 +214,10 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
>> struct generic_pm_domain *genpd = pd_to_genpd(pd);
>> struct gpd_link *link;
>>
>> - if (!genpd->max_off_time_changed)
>> + if (!genpd->max_off_time_changed) {
>> + genpd->state_idx = genpd->cached_power_down_state_idx;
>> return genpd->cached_power_down_ok;
>> + }
>>
>> /*
>> * We have to invalidate the cached results for the masters, so
>> @@ -240,6 +242,7 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
>> genpd->state_idx--;
>> }
>>
>> + genpd->cached_power_down_state_idx = genpd->state_idx;
>> return genpd->cached_power_down_ok;
>> }
>>
>> @@ -255,6 +258,10 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
>> s64 idle_duration_ns;
>> int cpu, i;
>>
>> + /* Validate dev PM QoS constraints. */
>> + if (!default_power_down_ok(pd))
>> + return false;
>> +
>> if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
>> return true;
>>
>> @@ -276,9 +283,9 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
>> /*
>> * Find the deepest idle state that has its residency value satisfied
>> * and by also taking into account the power off latency for the state.
>> - * Start at the deepest supported state.
>> + * Start at the state picked by the dev PM QoS constraint validation.
>> */
>> - i = genpd->state_count - 1;
>> + i = genpd->state_idx;
>> do {
>> if (!genpd->states[i].residency_ns)
>> break;
>> @@ -312,6 +319,6 @@ struct dev_power_governor pm_domain_always_on_gov = {
>> };
>>
>> struct dev_power_governor pm_domain_cpu_gov = {
>> - .suspend_ok = NULL,
>> + .suspend_ok = default_suspend_ok,
>> .power_down_ok = cpu_power_down_ok,
>> };
>> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
>> index 97901c833108..dbc69721cad8 100644
>> --- a/include/linux/pm_domain.h
>> +++ b/include/linux/pm_domain.h
>> @@ -81,6 +81,7 @@ struct generic_pm_domain {
>> s64 max_off_time_ns; /* Maximum allowed "suspended" time. */
>> bool max_off_time_changed;
>> bool cached_power_down_ok;
>> + bool cached_power_down_state_idx;
>> int (*attach_dev)(struct generic_pm_domain *domain,
>> struct device *dev);
>> void (*detach_dev)(struct generic_pm_domain *domain,
>>
>
> I don't see much value in splitting this patch off [07/26] and it actually
> confused me, so it may as well confuse someone else.
>

The idea was to let people, explicitly, comment on the whether dev PM
Qos constraints should be considered by the governor.

However, I get your point, let's combine them!

Kind regards
Uffe

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