| Message ID | 3615978.1OBBRZE5lx@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On 2017-11-07 at 02:23:18 +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > The genpd governor currently uses negative PM QoS values to indicate > the "no suspend" condition and 0 as "no restriction", but it doesn't > use them consistently. Moreover, it tries to refresh QoS values for > already suspended devices in a quite questionable way. > > For the above reasons, rework it to be a bit more consistent. > > First off, note that dev_pm_qos_read_value() in > dev_update_qos_constraint() and __default_power_down_ok() is > evaluated for devices in suspend. Moreover, that only happens if the > effective_constraint_ns value for them is negative (meaning "no > suspend"). It is not evaluated in any other cases, so effectively > the QoS values are only updated for devices in suspend that should > not have been suspended in the first place. In all of the other > cases, the QoS values taken into account are the effective ones from > the time before the device has been suspended, so generally devices > need to be resumed and suspended again for new QoS values to take > effect anyway. Thus evaluating dev_update_qos_constraint() in > those two places doesn't make sense at all, so drop it. > > Second, initialize effective_constraint_ns to 0 ("no constraint") > rather than to (-1) ("no suspend"), which makes more sense in > general and in case effective_constraint_ns is never updated > (the device is in suspend all the time or it is never suspended) > it doesn't affect the device's parent and so on. > > Finally, rework default_suspend_ok() to explicitly handle the > "no restriction" and "no suspend" special cases. > > Also add WARN_ON() around checks that should never trigger. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > > v2 -> v3: Take children that don't belong to genpd power domains into > account in dev_update_qos_constraint(). > > --- > drivers/base/power/domain.c | 2 > drivers/base/power/domain_governor.c | 71 ++++++++++++++++++++++++----------- > 2 files changed, 50 insertions(+), 23 deletions(-) > > Index: linux-pm/drivers/base/power/domain.c > =================================================================== > --- linux-pm.orig/drivers/base/power/domain.c > +++ linux-pm/drivers/base/power/domain.c > @@ -1331,7 +1331,7 @@ static struct generic_pm_domain_data *ge > > gpd_data->base.dev = dev; > gpd_data->td.constraint_changed = true; > - gpd_data->td.effective_constraint_ns = -1; > + gpd_data->td.effective_constraint_ns = 0; > gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; > > spin_lock_irq(&dev->power.lock); > Index: linux-pm/drivers/base/power/domain_governor.c > =================================================================== > --- linux-pm.orig/drivers/base/power/domain_governor.c > +++ linux-pm/drivers/base/power/domain_governor.c > @@ -14,22 +14,33 @@ > static int dev_update_qos_constraint(struct device *dev, void *data) > { > s64 *constraint_ns_p = data; > - s32 constraint_ns = -1; > + s64 constraint_ns; > > - if (dev->power.subsys_data && dev->power.subsys_data->domain_data) > + if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { > + /* > + * Only take suspend-time QoS constraints of devices into > + * account, because constraints updated after the device has > + * been suspended are not guaranteed to be taken into account > + * anyway. In order for them to take effect, the device has to > + * be resumed and suspended again. > + */ > constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; > - > - if (constraint_ns < 0) { > + } else { > + /* > + * The child is not in a domain and there's no info on its > + * suspend/resume latencies, so assume them to be negligible and > + * take its current PM QoS constraint (that's the only thing > + * known at this point anyway). > + */ > constraint_ns = dev_pm_qos_read_value(dev); > - constraint_ns *= NSEC_PER_USEC; > + if (constraint_ns > 0) > + constraint_ns *= NSEC_PER_USEC; > } > + > + /* 0 means "no constraint" */ > if (constraint_ns == 0) > return 0; > > - /* > - * constraint_ns cannot be negative here, because the device has been > - * suspended. > - */ > if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) > *constraint_ns_p = constraint_ns; > > @@ -76,14 +87,32 @@ static bool default_suspend_ok(struct de > device_for_each_child(dev, &constraint_ns, > dev_update_qos_constraint); > > - if (constraint_ns > 0) { > + if (constraint_ns == 0) { > + /* "No restriction", so the device is allowed to suspend. */ > + td->effective_constraint_ns = 0; > + td->cached_suspend_ok = true; > + } else if (constraint_ns < 0) { > + /* > + * This triggers if one of the children that don't belong to a > + * domain has a negative PM QoS constraint and it's better not > + * to suspend then. effective_constraint_ns is negative already > + * and cached_suspend_ok is false, so bail out. > + */ > + return false; This change is ok. However, would like to bring to your attention a possible inconsistency in the treatment of negative value as "no suspend at all" that can affect this. user level entry does not allow negative values. Only way to enter a negative value is if the kernel API to add/update is used. In that interface, if -1 (PM_QOS_DEFAULT_VALUE) is passed, pm_qos_update_target will actually assign the default value stored in the constraint. The default value is PM_QOS_RESUME_LATENCY_DEFAULT_VALUE which is 0. 0 means "no constraint". All this gets fixed in the next patch though. > + } else { > constraint_ns -= td->suspend_latency_ns + > td->resume_latency_ns; > - if (constraint_ns == 0) > + /* > + * effective_constraint_ns is negative already and > + * cached_suspend_ok is false, so if the computed value is not > + * positive, return right away. > + */ > + if (constraint_ns <= 0) > return false; > + > + td->effective_constraint_ns = constraint_ns; > + td->cached_suspend_ok = true; > } > - td->effective_constraint_ns = constraint_ns; > - td->cached_suspend_ok = constraint_ns >= 0; > > /* > * The children have been suspended already, so we don't need to take > @@ -144,18 +173,16 @@ static bool __default_power_down_ok(stru > */ > td = &to_gpd_data(pdd)->td; > constraint_ns = td->effective_constraint_ns; > - /* default_suspend_ok() need not be called before us. */ > - if (constraint_ns < 0) { > - constraint_ns = dev_pm_qos_read_value(pdd->dev); > - constraint_ns *= NSEC_PER_USEC; > - } > + /* > + * Negative values mean "no suspend at all" and this runs only > + * when all devices in the domain are suspended, so it must be > + * 0 at least. > + * > + * 0 means "no constraint" > + */ > if (constraint_ns == 0) > continue; > > - /* > - * constraint_ns cannot be negative here, because the device has > - * been suspended. > - */ > if (constraint_ns <= off_on_time_ns) > return false; > > Regards, Ramesh
On Tue, Nov 7, 2017 at 6:05 AM, Ramesh Thomas <ramesh.thomas@intel.com> wrote: > On 2017-11-07 at 02:23:18 +0100, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> >> The genpd governor currently uses negative PM QoS values to indicate >> the "no suspend" condition and 0 as "no restriction", but it doesn't >> use them consistently. Moreover, it tries to refresh QoS values for >> already suspended devices in a quite questionable way. >> >> For the above reasons, rework it to be a bit more consistent. >> >> First off, note that dev_pm_qos_read_value() in >> dev_update_qos_constraint() and __default_power_down_ok() is >> evaluated for devices in suspend. Moreover, that only happens if the >> effective_constraint_ns value for them is negative (meaning "no >> suspend"). It is not evaluated in any other cases, so effectively >> the QoS values are only updated for devices in suspend that should >> not have been suspended in the first place. In all of the other >> cases, the QoS values taken into account are the effective ones from >> the time before the device has been suspended, so generally devices >> need to be resumed and suspended again for new QoS values to take >> effect anyway. Thus evaluating dev_update_qos_constraint() in >> those two places doesn't make sense at all, so drop it. >> >> Second, initialize effective_constraint_ns to 0 ("no constraint") >> rather than to (-1) ("no suspend"), which makes more sense in >> general and in case effective_constraint_ns is never updated >> (the device is in suspend all the time or it is never suspended) >> it doesn't affect the device's parent and so on. >> >> Finally, rework default_suspend_ok() to explicitly handle the >> "no restriction" and "no suspend" special cases. >> >> Also add WARN_ON() around checks that should never trigger. >> >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> >> --- >> >> v2 -> v3: Take children that don't belong to genpd power domains into >> account in dev_update_qos_constraint(). >> >> --- >> drivers/base/power/domain.c | 2 >> drivers/base/power/domain_governor.c | 71 ++++++++++++++++++++++++----------- >> 2 files changed, 50 insertions(+), 23 deletions(-) >> >> Index: linux-pm/drivers/base/power/domain.c >> =================================================================== >> --- linux-pm.orig/drivers/base/power/domain.c >> +++ linux-pm/drivers/base/power/domain.c >> @@ -1331,7 +1331,7 @@ static struct generic_pm_domain_data *ge >> >> gpd_data->base.dev = dev; >> gpd_data->td.constraint_changed = true; >> - gpd_data->td.effective_constraint_ns = -1; >> + gpd_data->td.effective_constraint_ns = 0; >> gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; >> >> spin_lock_irq(&dev->power.lock); >> Index: linux-pm/drivers/base/power/domain_governor.c >> =================================================================== >> --- linux-pm.orig/drivers/base/power/domain_governor.c >> +++ linux-pm/drivers/base/power/domain_governor.c >> @@ -14,22 +14,33 @@ >> static int dev_update_qos_constraint(struct device *dev, void *data) >> { >> s64 *constraint_ns_p = data; >> - s32 constraint_ns = -1; >> + s64 constraint_ns; >> >> - if (dev->power.subsys_data && dev->power.subsys_data->domain_data) >> + if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { >> + /* >> + * Only take suspend-time QoS constraints of devices into >> + * account, because constraints updated after the device has >> + * been suspended are not guaranteed to be taken into account >> + * anyway. In order for them to take effect, the device has to >> + * be resumed and suspended again. >> + */ >> constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; >> - >> - if (constraint_ns < 0) { >> + } else { >> + /* >> + * The child is not in a domain and there's no info on its >> + * suspend/resume latencies, so assume them to be negligible and >> + * take its current PM QoS constraint (that's the only thing >> + * known at this point anyway). >> + */ >> constraint_ns = dev_pm_qos_read_value(dev); >> - constraint_ns *= NSEC_PER_USEC; >> + if (constraint_ns > 0) >> + constraint_ns *= NSEC_PER_USEC; >> } >> + >> + /* 0 means "no constraint" */ >> if (constraint_ns == 0) >> return 0; >> >> - /* >> - * constraint_ns cannot be negative here, because the device has been >> - * suspended. >> - */ >> if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) >> *constraint_ns_p = constraint_ns; >> >> @@ -76,14 +87,32 @@ static bool default_suspend_ok(struct de >> device_for_each_child(dev, &constraint_ns, >> dev_update_qos_constraint); >> >> - if (constraint_ns > 0) { >> + if (constraint_ns == 0) { >> + /* "No restriction", so the device is allowed to suspend. */ >> + td->effective_constraint_ns = 0; >> + td->cached_suspend_ok = true; >> + } else if (constraint_ns < 0) { >> + /* >> + * This triggers if one of the children that don't belong to a >> + * domain has a negative PM QoS constraint and it's better not >> + * to suspend then. effective_constraint_ns is negative already >> + * and cached_suspend_ok is false, so bail out. >> + */ >> + return false; > > This change is ok. However, would like to bring to your attention a possible > inconsistency in the treatment of negative value as "no suspend at all" that > can affect this. > > user level entry does not allow negative values. Only way to enter a negative > value is if the kernel API to add/update is used. In that interface, if -1 > (PM_QOS_DEFAULT_VALUE) is passed, pm_qos_update_target will actually assign > the default value stored in the constraint. The default value is > PM_QOS_RESUME_LATENCY_DEFAULT_VALUE which is 0. 0 means "no constraint". OK, but that only means that default_suspend_ok() will never see -1 as a value. It may see other negative values, though, and treating them as "no suspend" is not incorrect. So I don't think the patch needs to be updated. In any case, good catch! Thanks, Rafael
On 2017-11-07 at 11:22:48 +0100, Rafael J. Wysocki wrote: > On Tue, Nov 7, 2017 at 6:05 AM, Ramesh Thomas <ramesh.thomas@intel.com> wrote: > > On 2017-11-07 at 02:23:18 +0100, Rafael J. Wysocki wrote: > >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > >> > >> The genpd governor currently uses negative PM QoS values to indicate > >> the "no suspend" condition and 0 as "no restriction", but it doesn't > >> use them consistently. Moreover, it tries to refresh QoS values for > >> already suspended devices in a quite questionable way. > >> > >> For the above reasons, rework it to be a bit more consistent. > >> > >> First off, note that dev_pm_qos_read_value() in > >> dev_update_qos_constraint() and __default_power_down_ok() is > >> evaluated for devices in suspend. Moreover, that only happens if the > >> effective_constraint_ns value for them is negative (meaning "no > >> suspend"). It is not evaluated in any other cases, so effectively > >> the QoS values are only updated for devices in suspend that should > >> not have been suspended in the first place. In all of the other > >> cases, the QoS values taken into account are the effective ones from > >> the time before the device has been suspended, so generally devices > >> need to be resumed and suspended again for new QoS values to take > >> effect anyway. Thus evaluating dev_update_qos_constraint() in > >> those two places doesn't make sense at all, so drop it. > >> > >> Second, initialize effective_constraint_ns to 0 ("no constraint") > >> rather than to (-1) ("no suspend"), which makes more sense in > >> general and in case effective_constraint_ns is never updated > >> (the device is in suspend all the time or it is never suspended) > >> it doesn't affect the device's parent and so on. > >> > >> Finally, rework default_suspend_ok() to explicitly handle the > >> "no restriction" and "no suspend" special cases. > >> > >> Also add WARN_ON() around checks that should never trigger. > >> > >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > >> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> > >> --- > >> > >> v2 -> v3: Take children that don't belong to genpd power domains into > >> account in dev_update_qos_constraint(). > >> > >> --- > >> drivers/base/power/domain.c | 2 > >> drivers/base/power/domain_governor.c | 71 ++++++++++++++++++++++++----------- > >> 2 files changed, 50 insertions(+), 23 deletions(-) > >> > >> Index: linux-pm/drivers/base/power/domain.c > >> =================================================================== > >> --- linux-pm.orig/drivers/base/power/domain.c > >> +++ linux-pm/drivers/base/power/domain.c > >> @@ -1331,7 +1331,7 @@ static struct generic_pm_domain_data *ge > >> > >> gpd_data->base.dev = dev; > >> gpd_data->td.constraint_changed = true; > >> - gpd_data->td.effective_constraint_ns = -1; > >> + gpd_data->td.effective_constraint_ns = 0; > >> gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; > >> > >> spin_lock_irq(&dev->power.lock); > >> Index: linux-pm/drivers/base/power/domain_governor.c > >> =================================================================== > >> --- linux-pm.orig/drivers/base/power/domain_governor.c > >> +++ linux-pm/drivers/base/power/domain_governor.c > >> @@ -14,22 +14,33 @@ > >> static int dev_update_qos_constraint(struct device *dev, void *data) > >> { > >> s64 *constraint_ns_p = data; > >> - s32 constraint_ns = -1; > >> + s64 constraint_ns; > >> > >> - if (dev->power.subsys_data && dev->power.subsys_data->domain_data) > >> + if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { > >> + /* > >> + * Only take suspend-time QoS constraints of devices into > >> + * account, because constraints updated after the device has > >> + * been suspended are not guaranteed to be taken into account > >> + * anyway. In order for them to take effect, the device has to > >> + * be resumed and suspended again. > >> + */ > >> constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; > >> - > >> - if (constraint_ns < 0) { > >> + } else { > >> + /* > >> + * The child is not in a domain and there's no info on its > >> + * suspend/resume latencies, so assume them to be negligible and > >> + * take its current PM QoS constraint (that's the only thing > >> + * known at this point anyway). > >> + */ > >> constraint_ns = dev_pm_qos_read_value(dev); > >> - constraint_ns *= NSEC_PER_USEC; > >> + if (constraint_ns > 0) > >> + constraint_ns *= NSEC_PER_USEC; > >> } > >> + > >> + /* 0 means "no constraint" */ > >> if (constraint_ns == 0) > >> return 0; > >> > >> - /* > >> - * constraint_ns cannot be negative here, because the device has been > >> - * suspended. > >> - */ > >> if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) > >> *constraint_ns_p = constraint_ns; > >> > >> @@ -76,14 +87,32 @@ static bool default_suspend_ok(struct de > >> device_for_each_child(dev, &constraint_ns, > >> dev_update_qos_constraint); > >> > >> - if (constraint_ns > 0) { > >> + if (constraint_ns == 0) { > >> + /* "No restriction", so the device is allowed to suspend. */ > >> + td->effective_constraint_ns = 0; > >> + td->cached_suspend_ok = true; > >> + } else if (constraint_ns < 0) { > >> + /* > >> + * This triggers if one of the children that don't belong to a > >> + * domain has a negative PM QoS constraint and it's better not > >> + * to suspend then. effective_constraint_ns is negative already > >> + * and cached_suspend_ok is false, so bail out. > >> + */ > >> + return false; > > > > This change is ok. However, would like to bring to your attention a possible > > inconsistency in the treatment of negative value as "no suspend at all" that > > can affect this. > > > > user level entry does not allow negative values. Only way to enter a negative > > value is if the kernel API to add/update is used. In that interface, if -1 > > (PM_QOS_DEFAULT_VALUE) is passed, pm_qos_update_target will actually assign > > the default value stored in the constraint. The default value is > > PM_QOS_RESUME_LATENCY_DEFAULT_VALUE which is 0. 0 means "no constraint". > > OK, but that only means that default_suspend_ok() will never see -1 as > a value. It may see other negative values, though, and treating them > as "no suspend" is not incorrect. So I don't think the patch needs to > be updated. Right. The issue with -1 is a bug at another place and the second patch fixes that anyway. Looks good to me. Reviewed-by: Ramesh Thomas <ramesh.thomas@intel.com> Thanks, Ramesh > > In any case, good catch! > > Thanks, > Rafael
On 7 November 2017 at 02:23, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > The genpd governor currently uses negative PM QoS values to indicate > the "no suspend" condition and 0 as "no restriction", but it doesn't > use them consistently. Moreover, it tries to refresh QoS values for > already suspended devices in a quite questionable way. > > For the above reasons, rework it to be a bit more consistent. > > First off, note that dev_pm_qos_read_value() in > dev_update_qos_constraint() and __default_power_down_ok() is > evaluated for devices in suspend. Moreover, that only happens if the > effective_constraint_ns value for them is negative (meaning "no > suspend"). It is not evaluated in any other cases, so effectively > the QoS values are only updated for devices in suspend that should > not have been suspended in the first place. In all of the other > cases, the QoS values taken into account are the effective ones from > the time before the device has been suspended, so generally devices > need to be resumed and suspended again for new QoS values to take > effect anyway. Thus evaluating dev_update_qos_constraint() in > those two places doesn't make sense at all, so drop it. > > Second, initialize effective_constraint_ns to 0 ("no constraint") > rather than to (-1) ("no suspend"), which makes more sense in > general and in case effective_constraint_ns is never updated > (the device is in suspend all the time or it is never suspended) > it doesn't affect the device's parent and so on. > > Finally, rework default_suspend_ok() to explicitly handle the > "no restriction" and "no suspend" special cases. > > Also add WARN_ON() around checks that should never trigger. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Ulf Hansson <ulf.hansson@linaro.org> Kind regards Uffe > --- > > v2 -> v3: Take children that don't belong to genpd power domains into > account in dev_update_qos_constraint(). > > --- > drivers/base/power/domain.c | 2 > drivers/base/power/domain_governor.c | 71 ++++++++++++++++++++++++----------- > 2 files changed, 50 insertions(+), 23 deletions(-) > > Index: linux-pm/drivers/base/power/domain.c > =================================================================== > --- linux-pm.orig/drivers/base/power/domain.c > +++ linux-pm/drivers/base/power/domain.c > @@ -1331,7 +1331,7 @@ static struct generic_pm_domain_data *ge > > gpd_data->base.dev = dev; > gpd_data->td.constraint_changed = true; > - gpd_data->td.effective_constraint_ns = -1; > + gpd_data->td.effective_constraint_ns = 0; > gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; > > spin_lock_irq(&dev->power.lock); > Index: linux-pm/drivers/base/power/domain_governor.c > =================================================================== > --- linux-pm.orig/drivers/base/power/domain_governor.c > +++ linux-pm/drivers/base/power/domain_governor.c > @@ -14,22 +14,33 @@ > static int dev_update_qos_constraint(struct device *dev, void *data) > { > s64 *constraint_ns_p = data; > - s32 constraint_ns = -1; > + s64 constraint_ns; > > - if (dev->power.subsys_data && dev->power.subsys_data->domain_data) > + if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { > + /* > + * Only take suspend-time QoS constraints of devices into > + * account, because constraints updated after the device has > + * been suspended are not guaranteed to be taken into account > + * anyway. In order for them to take effect, the device has to > + * be resumed and suspended again. > + */ > constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; > - > - if (constraint_ns < 0) { > + } else { > + /* > + * The child is not in a domain and there's no info on its > + * suspend/resume latencies, so assume them to be negligible and > + * take its current PM QoS constraint (that's the only thing > + * known at this point anyway). > + */ > constraint_ns = dev_pm_qos_read_value(dev); > - constraint_ns *= NSEC_PER_USEC; > + if (constraint_ns > 0) > + constraint_ns *= NSEC_PER_USEC; > } > + > + /* 0 means "no constraint" */ > if (constraint_ns == 0) > return 0; > > - /* > - * constraint_ns cannot be negative here, because the device has been > - * suspended. > - */ > if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) > *constraint_ns_p = constraint_ns; > > @@ -76,14 +87,32 @@ static bool default_suspend_ok(struct de > device_for_each_child(dev, &constraint_ns, > dev_update_qos_constraint); > > - if (constraint_ns > 0) { > + if (constraint_ns == 0) { > + /* "No restriction", so the device is allowed to suspend. */ > + td->effective_constraint_ns = 0; > + td->cached_suspend_ok = true; > + } else if (constraint_ns < 0) { > + /* > + * This triggers if one of the children that don't belong to a > + * domain has a negative PM QoS constraint and it's better not > + * to suspend then. effective_constraint_ns is negative already > + * and cached_suspend_ok is false, so bail out. > + */ > + return false; > + } else { > constraint_ns -= td->suspend_latency_ns + > td->resume_latency_ns; > - if (constraint_ns == 0) > + /* > + * effective_constraint_ns is negative already and > + * cached_suspend_ok is false, so if the computed value is not > + * positive, return right away. > + */ > + if (constraint_ns <= 0) > return false; > + > + td->effective_constraint_ns = constraint_ns; > + td->cached_suspend_ok = true; > } > - td->effective_constraint_ns = constraint_ns; > - td->cached_suspend_ok = constraint_ns >= 0; > > /* > * The children have been suspended already, so we don't need to take > @@ -144,18 +173,16 @@ static bool __default_power_down_ok(stru > */ > td = &to_gpd_data(pdd)->td; > constraint_ns = td->effective_constraint_ns; > - /* default_suspend_ok() need not be called before us. */ > - if (constraint_ns < 0) { > - constraint_ns = dev_pm_qos_read_value(pdd->dev); > - constraint_ns *= NSEC_PER_USEC; > - } > + /* > + * Negative values mean "no suspend at all" and this runs only > + * when all devices in the domain are suspended, so it must be > + * 0 at least. > + * > + * 0 means "no constraint" > + */ > if (constraint_ns == 0) > continue; > > - /* > - * constraint_ns cannot be negative here, because the device has > - * been suspended. > - */ > if (constraint_ns <= off_on_time_ns) > return false; > >
Index: linux-pm/drivers/base/power/domain.c =================================================================== --- linux-pm.orig/drivers/base/power/domain.c +++ linux-pm/drivers/base/power/domain.c @@ -1331,7 +1331,7 @@ static struct generic_pm_domain_data *ge gpd_data->base.dev = dev; gpd_data->td.constraint_changed = true; - gpd_data->td.effective_constraint_ns = -1; + gpd_data->td.effective_constraint_ns = 0; gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; spin_lock_irq(&dev->power.lock); Index: linux-pm/drivers/base/power/domain_governor.c =================================================================== --- linux-pm.orig/drivers/base/power/domain_governor.c +++ linux-pm/drivers/base/power/domain_governor.c @@ -14,22 +14,33 @@ static int dev_update_qos_constraint(struct device *dev, void *data) { s64 *constraint_ns_p = data; - s32 constraint_ns = -1; + s64 constraint_ns; - if (dev->power.subsys_data && dev->power.subsys_data->domain_data) + if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { + /* + * Only take suspend-time QoS constraints of devices into + * account, because constraints updated after the device has + * been suspended are not guaranteed to be taken into account + * anyway. In order for them to take effect, the device has to + * be resumed and suspended again. + */ constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; - - if (constraint_ns < 0) { + } else { + /* + * The child is not in a domain and there's no info on its + * suspend/resume latencies, so assume them to be negligible and + * take its current PM QoS constraint (that's the only thing + * known at this point anyway). + */ constraint_ns = dev_pm_qos_read_value(dev); - constraint_ns *= NSEC_PER_USEC; + if (constraint_ns > 0) + constraint_ns *= NSEC_PER_USEC; } + + /* 0 means "no constraint" */ if (constraint_ns == 0) return 0; - /* - * constraint_ns cannot be negative here, because the device has been - * suspended. - */ if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) *constraint_ns_p = constraint_ns; @@ -76,14 +87,32 @@ static bool default_suspend_ok(struct de device_for_each_child(dev, &constraint_ns, dev_update_qos_constraint); - if (constraint_ns > 0) { + if (constraint_ns == 0) { + /* "No restriction", so the device is allowed to suspend. */ + td->effective_constraint_ns = 0; + td->cached_suspend_ok = true; + } else if (constraint_ns < 0) { + /* + * This triggers if one of the children that don't belong to a + * domain has a negative PM QoS constraint and it's better not + * to suspend then. effective_constraint_ns is negative already + * and cached_suspend_ok is false, so bail out. + */ + return false; + } else { constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns; - if (constraint_ns == 0) + /* + * effective_constraint_ns is negative already and + * cached_suspend_ok is false, so if the computed value is not + * positive, return right away. + */ + if (constraint_ns <= 0) return false; + + td->effective_constraint_ns = constraint_ns; + td->cached_suspend_ok = true; } - td->effective_constraint_ns = constraint_ns; - td->cached_suspend_ok = constraint_ns >= 0; /* * The children have been suspended already, so we don't need to take @@ -144,18 +173,16 @@ static bool __default_power_down_ok(stru */ td = &to_gpd_data(pdd)->td; constraint_ns = td->effective_constraint_ns; - /* default_suspend_ok() need not be called before us. */ - if (constraint_ns < 0) { - constraint_ns = dev_pm_qos_read_value(pdd->dev); - constraint_ns *= NSEC_PER_USEC; - } + /* + * Negative values mean "no suspend at all" and this runs only + * when all devices in the domain are suspended, so it must be + * 0 at least. + * + * 0 means "no constraint" + */ if (constraint_ns == 0) continue; - /* - * constraint_ns cannot be negative here, because the device has - * been suspended. - */ if (constraint_ns <= off_on_time_ns) return false;