| Message ID | 1726767.L8TO24juDO@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
[...] >> > >> > It actually should work with the ACPI PM domain code as is except that it >> > will cause the device to be runtime resumed every time during suspend. >> > >> > But acpi_subsys_suspend() can be changed to avoid resuming the device if >> > power.force_suspend is set. >> >> Or better yet, if power.direct_complete is not set, because that means the >> device needs to be resumed anyway. >> >> And if power.direct_complete is set at that point, power.force_suspend has to >> be set too. I believe I understand your goal here. You want to consider if it is possible to extend the behavior of the direct_complete path, instead of enabling the runtime PM centric path for the ACPI PM domain, to accomplish the same optimizations. I think the answer to that, is that it simply can't. See more information about why further down below. > > Overall, like below, and of course drivers that ser power.force_suspend need to > be able to deal with devices that have been runtime resumed during > __device_suspend(). The a concern I see with this approach, is that is going to be too complex to understand. We have already seen how the i2c-designware-driver was screwed up when it was trying to take advantage of the optimizations provided by the current direct_complete path. I think we should be careful when considering making it even more complex. In the runtime PM centric path, driver authors can easily deploy system sleep support. In some cases it may even consists of only two lines of code. As can be shown in patch9 for the i2c driver. Just to be clear, that doesn't mean that I think the direct_complete path isn't useful. Especially it is a good match for the ACPI PM domain, as it can easily affect all its devices, without having to care much about the behavior of the drivers. > > --- > drivers/acpi/device_pm.c | 8 ++++++++ > drivers/base/power/main.c | 11 +++++++++-- > include/linux/pm.h | 1 + > 3 files changed, 18 insertions(+), 2 deletions(-) > > Index: linux-pm/drivers/base/power/main.c > =================================================================== > --- linux-pm.orig/drivers/base/power/main.c > +++ linux-pm/drivers/base/power/main.c > @@ -1271,9 +1271,16 @@ static int __device_suspend_late(struct > goto Complete; > } > > - if (dev->power.syscore || dev->power.direct_complete) > + if (dev->power.syscore) > goto Complete; > > + if (dev->power.direct_complete) { > + if (pm_runtime_status_suspended(dev)) > + goto Complete; > + > + dev->power.direct_complete = false; > + } > + > if (dev->pm_domain) { > info = "late power domain "; > callback = pm_late_early_op(&dev->pm_domain->ops, state); > @@ -1482,7 +1489,7 @@ static int __device_suspend(struct devic > if (dev->power.syscore) > goto Complete; > > - if (dev->power.direct_complete) { > + if (dev->power.direct_complete && !dev->power.force_suspend) { > if (pm_runtime_status_suspended(dev)) { > pm_runtime_disable(dev); > if (pm_runtime_status_suspended(dev)) > Index: linux-pm/include/linux/pm.h > =================================================================== > --- linux-pm.orig/include/linux/pm.h > +++ linux-pm/include/linux/pm.h > @@ -554,6 +554,7 @@ struct dev_pm_info { > pm_message_t power_state; > unsigned int can_wakeup:1; > unsigned int async_suspend:1; > + unsigned int force_suspend:1; > bool in_dpm_list:1; /* Owned by the PM core */ > bool is_prepared:1; /* Owned by the PM core */ > bool is_suspended:1; /* Ditto */ > Index: linux-pm/drivers/acpi/device_pm.c > =================================================================== > --- linux-pm.orig/drivers/acpi/device_pm.c > +++ linux-pm/drivers/acpi/device_pm.c > @@ -1025,9 +1025,17 @@ EXPORT_SYMBOL_GPL(acpi_subsys_prepare); > * > * Follow PCI and resume devices suspended at run time before running their > * system suspend callbacks. > + * > + * If the power.direct_complete flag is set for the device, though, skip all > + * that, because the device doesn't need to be resumed then and if it is > + * resumed via runtime PM, the core will notice that and will carry out the > + * late suspend for it. > */ > int acpi_subsys_suspend(struct device *dev) > { > + if (dev->power.direct_complete) > + return 0; > + > pm_runtime_resume(dev); > return pm_generic_suspend(dev); > } > The above change would offer an improvement, however there are more benefits from the runtime PM centric path that it doesn't cover. The below is pasted from the changelog for patch9 (I will make sure to fold in this in the changelog for $subject patch next version). In case the device is/gets runtime resumed before the device_suspend() phase is entered, the PM core doesn't run the direct_complete path for the device during system sleep. During system resume, this lead to that the device will always be brought back to full power when the i2c-dw-plat driver's ->resume() callback is invoked. This may not be necessary, thus increasing the resume time for the device and wasting power. In the runtime PM centric path, the pm_runtime_force_resume() helper takes better care, as it resumes the device only in case it's really needed. Normally this means it can be postponed to be dealt with via regular calls to runtime PM (pm_runtime_get*()) instead. In other words, the device remains in its low power state until someone request a new i2c transfer, whenever that may be. As far as I can think of, the direct_complete path can't be adjusted to support this. Or can it? Kind regards Uffe
Index: linux-pm/drivers/base/power/main.c =================================================================== --- linux-pm.orig/drivers/base/power/main.c +++ linux-pm/drivers/base/power/main.c @@ -1271,9 +1271,16 @@ static int __device_suspend_late(struct goto Complete; } - if (dev->power.syscore || dev->power.direct_complete) + if (dev->power.syscore) goto Complete; + if (dev->power.direct_complete) { + if (pm_runtime_status_suspended(dev)) + goto Complete; + + dev->power.direct_complete = false; + } + if (dev->pm_domain) { info = "late power domain "; callback = pm_late_early_op(&dev->pm_domain->ops, state); @@ -1482,7 +1489,7 @@ static int __device_suspend(struct devic if (dev->power.syscore) goto Complete; - if (dev->power.direct_complete) { + if (dev->power.direct_complete && !dev->power.force_suspend) { if (pm_runtime_status_suspended(dev)) { pm_runtime_disable(dev); if (pm_runtime_status_suspended(dev)) Index: linux-pm/include/linux/pm.h =================================================================== --- linux-pm.orig/include/linux/pm.h +++ linux-pm/include/linux/pm.h @@ -554,6 +554,7 @@ struct dev_pm_info { pm_message_t power_state; unsigned int can_wakeup:1; unsigned int async_suspend:1; + unsigned int force_suspend:1; bool in_dpm_list:1; /* Owned by the PM core */ bool is_prepared:1; /* Owned by the PM core */ bool is_suspended:1; /* Ditto */ Index: linux-pm/drivers/acpi/device_pm.c =================================================================== --- linux-pm.orig/drivers/acpi/device_pm.c +++ linux-pm/drivers/acpi/device_pm.c @@ -1025,9 +1025,17 @@ EXPORT_SYMBOL_GPL(acpi_subsys_prepare); * * Follow PCI and resume devices suspended at run time before running their * system suspend callbacks. + * + * If the power.direct_complete flag is set for the device, though, skip all + * that, because the device doesn't need to be resumed then and if it is + * resumed via runtime PM, the core will notice that and will carry out the + * late suspend for it. */ int acpi_subsys_suspend(struct device *dev) { + if (dev->power.direct_complete) + return 0; + pm_runtime_resume(dev); return pm_generic_suspend(dev); }