On 20 October 2015 at 21:26, <[email protected]> wrote:
> From: Axel Haslam <[email protected]>
>
> Now that the structures of genpd can support multiple state definitions,
> add the logic in the governor to select the deepest possible state when
> powering down.
>
> For this, create the new function power_down_ok_for_state which will test
> if a particular state will not violate the devices and sub-domains
> constraints.
>
> default_power_down_ok is modified to try each state starting from the
> deepest until a valid state is found or there are no more states to test.
>
> the resulting state will be valid until there are latency or constraint
> changes, thus, we can avoid looping every power_down, and use the cached
> results instead.
>
> Signed-off-by: Axel Haslam <[email protected]>
> ---
> drivers/base/power/domain_governor.c | 75 +++++++++++++++++++++---------------
> 1 file changed, 45 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/base/power/domain_governor.c b/drivers/base/power/domain_governor.c
> index bf3ac68..aab2b32 100644
> --- a/drivers/base/power/domain_governor.c
> +++ b/drivers/base/power/domain_governor.c
> @@ -100,7 +100,8 @@ static bool default_stop_ok(struct device *dev)
> *
> * This routine must be executed under the PM domain's lock.
> */
> -static bool default_power_down_ok(struct dev_pm_domain *pd)
> +static bool power_down_ok_for_state(struct dev_pm_domain *pd,
> + unsigned int state)
> {
> struct generic_pm_domain *genpd = pd_to_genpd(pd);
> struct gpd_link *link;
> @@ -108,31 +109,9 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
> s64 min_off_time_ns;
> s64 off_on_time_ns;
>
> - if (genpd->max_off_time_changed) {
> - struct gpd_link *link;
> + off_on_time_ns = genpd->states[state].power_off_latency_ns +
> + genpd->states[state].power_on_latency_ns;
>
> - /*
> - * We have to invalidate the cached results for the masters, so
> - * use the observation that default_power_down_ok() is not
> - * going to be called for any master until this instance
> - * returns.
> - */
> - list_for_each_entry(link, &genpd->slave_links, slave_node)
> - link->master->max_off_time_changed = true;
> -
> - genpd->max_off_time_changed = false;
> - genpd->cached_power_down_ok = false;
> - genpd->max_off_time_ns = -1;
> - } else {
> - return genpd->cached_power_down_ok;
> - }
> -
> - /*
> - * Use the only available state, until multiple state support is added
> - * to the governor.
> - */
> - off_on_time_ns = genpd->states[0].power_off_latency_ns +
> - genpd->states[0].power_on_latency_ns;
>
> min_off_time_ns = -1;
> /*
> @@ -195,8 +174,6 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
> min_off_time_ns = constraint_ns;
> }
>
> - genpd->cached_power_down_ok = true;
> -
> /*
> * If the computed minimum device off time is negative, there are no
> * latency constraints, so the domain can spend arbitrary time in the
> @@ -209,14 +186,52 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
> * The difference between the computed minimum subdomain or device off
> * time and the time needed to turn the domain on is the maximum
> * theoretical time this domain can spend in the "off" state.
> - * Use the only available state, until multiple state support is added
> - * to the governor.
> */
> genpd->max_off_time_ns = min_off_time_ns -
> - genpd->states[0].power_on_latency_ns;
> + genpd->states[state].power_on_latency_ns;
> return true;
> }
[question]: Does it mean that the sleep level is just decided by
comparing the pre-configure on_off time with the gpd_timing_data? How
about the next timer event which affect the sleep depth on cpuidle
framework?
>
> +static bool default_power_down_ok(struct dev_pm_domain *pd)
> +{
> + struct generic_pm_domain *genpd = pd_to_genpd(pd);
> + unsigned int last_state_idx = genpd->state_count - 1;
> + struct gpd_link *link;
> + bool retval = false;
> + unsigned int i;
> +
> + /*
> + * if there was no change on max_off_time, we can return the
> + * cached value and we dont need to find a new target_state
> + */
> + if (!genpd->max_off_time_changed)
> + return genpd->cached_power_down_ok;
> +
> + /*
> + * We have to invalidate the cached results for the masters, so
> + * use the observation that default_power_down_ok() is not
> + * going to be called for any master until this instance
> + * returns.
> + */
> + list_for_each_entry(link, &genpd->slave_links, slave_node)
> + link->master->max_off_time_changed = true;
> +
> + genpd->max_off_time_ns = -1;
> + genpd->max_off_time_changed = false;
> +
> + /* find a state to power down to, starting from the deepest */
> + for (i = 0; i < genpd->state_count; i++) {
> + if (power_down_ok_for_state(pd, last_state_idx - i)) {
> + genpd->state_idx = last_state_idx - i;
> + retval = true;
> + break;
> + }
> + }
> +
> + genpd->cached_power_down_ok = retval;
> + return retval;
> +}
> +
> static bool always_on_power_down_ok(struct dev_pm_domain *domain)
> {
> return false;
[question]How the TICK_NOHZ treated if we substitute cpuidle framework
with this one?
> --
> 2.4.5
>
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Hi Zhaoyang,
>> @@ -209,14 +186,52 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
>> * The difference between the computed minimum subdomain or device off
>> * time and the time needed to turn the domain on is the maximum
>> * theoretical time this domain can spend in the "off" state.
>> - * Use the only available state, until multiple state support is added
>> - * to the governor.
>> */
>> genpd->max_off_time_ns = min_off_time_ns -
>> - genpd->states[0].power_on_latency_ns;
>> + genpd->states[state].power_on_latency_ns;
>> return true;
>> }
> [question]: Does it mean that the sleep level is just decided by
> comparing the pre-configure on_off time with the gpd_timing_data? How
> about the next timer event which affect the sleep depth on cpuidle
> framework?
There are a couple of patches on the list ill try to summarize
what i understand, Lina, Marc please correct me if im wrong!
I did this patches thinking generally about devices in a power domain
and not so much about a cpu. So these patches are not aimed at replacing
cpuidle, but were meant for power domains that may have intermediate
states, for example some logic may be implemented with retention flip-flops.
There is the proposal by Lina [1] to add cpus clusters to powerdomins
and by Marc[2] that tie cluster idle states to the powerdomain handler.
but i think the effort here is to complement cpuidle rather than to
replace it.
regards
Axel
1. https://lwn.net/Articles/653579/
2. https://lwn.net/Articles/658461/
>>
>> +static bool default_power_down_ok(struct dev_pm_domain *pd)
>> +{
>> + struct generic_pm_domain *genpd = pd_to_genpd(pd);
>> + unsigned int last_state_idx = genpd->state_count - 1;
>> + struct gpd_link *link;
>> + bool retval = false;
>> + unsigned int i;
>> +
>> + /*
>> + * if there was no change on max_off_time, we can return the
>> + * cached value and we dont need to find a new target_state
>> + */
>> + if (!genpd->max_off_time_changed)
>> + return genpd->cached_power_down_ok;
>> +
>> + /*
>> + * We have to invalidate the cached results for the masters, so
>> + * use the observation that default_power_down_ok() is not
>> + * going to be called for any master until this instance
>> + * returns.
>> + */
>> + list_for_each_entry(link, &genpd->slave_links, slave_node)
>> + link->master->max_off_time_changed = true;
>> +
>> + genpd->max_off_time_ns = -1;
>> + genpd->max_off_time_changed = false;
>> +
>> + /* find a state to power down to, starting from the deepest */
>> + for (i = 0; i < genpd->state_count; i++) {
>> + if (power_down_ok_for_state(pd, last_state_idx - i)) {
>> + genpd->state_idx = last_state_idx - i;
>> + retval = true;
>> + break;
>> + }
>> + }
>> +
>> + genpd->cached_power_down_ok = retval;
>> + return retval;
>> +}
>> +
>> static bool always_on_power_down_ok(struct dev_pm_domain *domain)
>> {
>> return false;
> [question]How the TICK_NOHZ treated if we substitute cpuidle framework
> with this one?
>> --
>> 2.4.5
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html