| Message ID | 20140516082055.40cd2bb4@ultegra (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Friday, May 16, 2014 08:20:55 AM Jacob Pan wrote: > On Thu, 15 May 2014 11:58:55 -0400 (EDT) > Alan Stern <stern@rowland.harvard.edu> wrote: > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > On Thu, 15 May 2014 10:29:42 -0400 (EDT) > > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > > > > > should we respect ignore_children flag here? not all parent > > > > > > > devices create children with proper .prepare() function. > > > > > > > this allows parents override children. > > > > > > > I am looking at USB, a USB device could have logical > > > > > > > children such as ep_xx, they don't go through the same > > > > > > > subsystem .prepare(). > > > > > > > > > > > > Well, I'm not sure about that. Let me consider that for a > > > > > > while. > > > > > OK. let me be more clear about the situation i see in USB. > > > > > Correct me if I am wrong, a USB device will always has at least > > > > > one endpoint/ep_00 as a kid for control pipe, it is a logical > > > > > device. So when device_prepare() is called, its call back is > > > > > NULL which makes .direct_complete = 0. Since children device > > > > > suspend is called before parents, the parents .direct_complete > > > > > flag will always get cleared. > > > > > > > > > > What i am trying to achieve here is to see if we avoid resuming > > > > > built-in (hardwired connect_type) non-hub USB devices based on > > > > > this new patchset. E.g. we don't want to resume/suspend USB > > > > > camera every time in system suspend/resume cycle if they are > > > > > already rpm suspended. We can save ~100ms resume time for the > > > > > devices we have tested. > > > > > > > > This is a good point, but I don't think it is at all related to > > > > ignore_children. > > > > > > > > Instead, it seems that the best way to solve it would be to add a > > > > ->prepare() handler for usb_ep_device_type that would always turn > > > > on direct_complete. > > > > > > > yeah, that would solve the problem with EP device type. But what > > > about other subdevices. e.g. for USB camera, uvcvideo device? We > > > can add .prepare(return 1;) for each level but would it be better > > > to have a flag similar to ignore_children if not ignore_children > > > itself. > > > > Something like that could always be added. > or, how about if a device's .prepare() is NULL, we could > assume .direct_resume() should be set. i.e. You mean direct_complete (which is a flag, not a function), I suppose? Wouldn't that go a bit too far? It seems to be based on the assumption that all devices having no ->prepare() callback can be safely left in runtime suspend over a system suspend/resume cycle, but is that assumption actually satisfied for all such devices? > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -1539,7 +1539,7 @@ static int device_prepare(struct device *dev, > pm_message_t state) pm_runtime_put(dev); > return ret; > } > - dev->power.direct_complete = ret > 0 && state.event == > PM_EVENT_SUSPEND > + dev->power.direct_complete = (!callback || ret > 0) && > state.event == PM_EVENT_SUSPEND && pm_runtime_suspended(dev); > dev_dbg(dev, "%s:direct_complete %d, info %s\n", __func__, > dev->power.direct_complete, info); > > > > > > Actually, I don't understand why this is not related to > > > ignore_children. Could you explain? > > > > It's hard to explain why two things are totally separate. Much > > better for you to describe why you think they _are_ related, so that > > I can explain how you are wrong. > > > > > If the parent knows it can ignore children and already rpm > > > suspended, why do we still ask children? > > > > The "ignore_children" flag doesn't mean that the parent can ignore > > its children. It means that the PM core is allowed to do a runtime > > suspend of the parent while leaving the children at full power. > > > > In particular, it doesn't mean that the children's ->suspend() > > callback will work correctly if it is called while the parent is > > runtime suspended. > that explains my question about ignore_chilren flag. thanks. > > > > Alan Stern > > > > [Jacob Pan] > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 16 May 2014 23:08:01 +0200 "Rafael J. Wysocki" <rjw@rjwysocki.net> wrote: > On Friday, May 16, 2014 08:20:55 AM Jacob Pan wrote: > > On Thu, 15 May 2014 11:58:55 -0400 (EDT) > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > On Thu, 15 May 2014 10:29:42 -0400 (EDT) > > > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > > > > > > > should we respect ignore_children flag here? not all > > > > > > > > parent devices create children with proper .prepare() > > > > > > > > function. this allows parents override children. > > > > > > > > I am looking at USB, a USB device could have logical > > > > > > > > children such as ep_xx, they don't go through the same > > > > > > > > subsystem .prepare(). > > > > > > > > > > > > > > Well, I'm not sure about that. Let me consider that for a > > > > > > > while. > > > > > > OK. let me be more clear about the situation i see in USB. > > > > > > Correct me if I am wrong, a USB device will always has at > > > > > > least one endpoint/ep_00 as a kid for control pipe, it is a > > > > > > logical device. So when device_prepare() is called, its > > > > > > call back is NULL which makes .direct_complete = 0. Since > > > > > > children device suspend is called before parents, the > > > > > > parents .direct_complete flag will always get cleared. > > > > > > > > > > > > What i am trying to achieve here is to see if we avoid > > > > > > resuming built-in (hardwired connect_type) non-hub USB > > > > > > devices based on this new patchset. E.g. we don't want to > > > > > > resume/suspend USB camera every time in system > > > > > > suspend/resume cycle if they are already rpm suspended. We > > > > > > can save ~100ms resume time for the devices we have tested. > > > > > > > > > > This is a good point, but I don't think it is at all related > > > > > to ignore_children. > > > > > > > > > > Instead, it seems that the best way to solve it would be to > > > > > add a ->prepare() handler for usb_ep_device_type that would > > > > > always turn on direct_complete. > > > > > > > > > yeah, that would solve the problem with EP device type. But what > > > > about other subdevices. e.g. for USB camera, uvcvideo device? We > > > > can add .prepare(return 1;) for each level but would it be > > > > better to have a flag similar to ignore_children if not > > > > ignore_children itself. > > > > > > Something like that could always be added. > > or, how about if a device's .prepare() is NULL, we could > > assume .direct_resume() should be set. i.e. > > You mean direct_complete (which is a flag, not a function), I suppose? > yes. > Wouldn't that go a bit too far? It seems to be based on the > assumption that all devices having no ->prepare() callback can be > safely left in runtime suspend over a system suspend/resume cycle, > but is that assumption actually satisfied for all such devices? > yes, I agree it is risky though i don't see problems with my limited testing. But on the other side, it is too strict. I also tried adding .prepare( return 1;) to usb_ep_device_type pm ops, that didn't work either. The reason is that ep devices don't support runtime pm (disable_depth > 0). I think in this case ignore_children flag should be the right indicator to ignore pm_runtime_suspended()? > > --- a/drivers/base/power/main.c > > +++ b/drivers/base/power/main.c > > @@ -1539,7 +1539,7 @@ static int device_prepare(struct device *dev, > > pm_message_t state) pm_runtime_put(dev); > > return ret; > > } > > - dev->power.direct_complete = ret > 0 && state.event == > > PM_EVENT_SUSPEND > > + dev->power.direct_complete = (!callback || ret > 0) && > > state.event == PM_EVENT_SUSPEND && pm_runtime_suspended(dev); > > dev_dbg(dev, "%s:direct_complete %d, info %s\n", __func__, > > dev->power.direct_complete, info); > > > > > > > > > Actually, I don't understand why this is not related to > > > > ignore_children. Could you explain? > > > > > > It's hard to explain why two things are totally separate. Much > > > better for you to describe why you think they _are_ related, so > > > that I can explain how you are wrong. > > > > > > > If the parent knows it can ignore children and already rpm > > > > suspended, why do we still ask children? > > > > > > The "ignore_children" flag doesn't mean that the parent can ignore > > > its children. It means that the PM core is allowed to do a > > > runtime suspend of the parent while leaving the children at full > > > power. > > > > > > In particular, it doesn't mean that the children's ->suspend() > > > callback will work correctly if it is called while the parent is > > > runtime suspended. > > that explains my question about ignore_chilren flag. thanks. > > > > > > Alan Stern > > > > > > > [Jacob Pan] > > -- > > To unsubscribe from this list: send the line "unsubscribe > > linux-acpi" in the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > [Jacob Pan] -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 19 May 2014, Jacob Pan wrote: > > Wouldn't that go a bit too far? It seems to be based on the > > assumption that all devices having no ->prepare() callback can be > > safely left in runtime suspend over a system suspend/resume cycle, > > but is that assumption actually satisfied for all such devices? > > > yes, I agree it is risky though i don't see problems with my limited > testing. But on the other side, it is too strict. > I also tried adding .prepare( return 1;) to usb_ep_device_type pm ops, > that didn't work either. The reason is that ep devices don't support > runtime pm (disable_depth > 0). I think in this case ignore_children > flag should be the right indicator to ignore pm_runtime_suspended()? Maybe it would be better to add a new flag that means "This is a virtual device and the PM core can ignore it completely". Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Monday, May 19, 2014 03:53:58 PM Alan Stern wrote: > On Mon, 19 May 2014, Jacob Pan wrote: > > > > Wouldn't that go a bit too far? It seems to be based on the > > > assumption that all devices having no ->prepare() callback can be > > > safely left in runtime suspend over a system suspend/resume cycle, > > > but is that assumption actually satisfied for all such devices? > > > > > yes, I agree it is risky though i don't see problems with my limited > > testing. But on the other side, it is too strict. > > I also tried adding .prepare( return 1;) to usb_ep_device_type pm ops, > > that didn't work either. The reason is that ep devices don't support > > runtime pm (disable_depth > 0). I think in this case ignore_children > > flag should be the right indicator to ignore pm_runtime_suspended()? > > Maybe it would be better to add a new flag that means "This is a > virtual device and the PM core can ignore it completely". I like that idea. :-) Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Monday, May 19, 2014 02:18:31 AM Jacob Pan wrote: > On Fri, 16 May 2014 23:08:01 +0200 > "Rafael J. Wysocki" <rjw@rjwysocki.net> wrote: > > > On Friday, May 16, 2014 08:20:55 AM Jacob Pan wrote: > > > On Thu, 15 May 2014 11:58:55 -0400 (EDT) > > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > > > On Thu, 15 May 2014 10:29:42 -0400 (EDT) > > > > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > > > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > > > > > > > > > should we respect ignore_children flag here? not all > > > > > > > > > parent devices create children with proper .prepare() > > > > > > > > > function. this allows parents override children. > > > > > > > > > I am looking at USB, a USB device could have logical > > > > > > > > > children such as ep_xx, they don't go through the same > > > > > > > > > subsystem .prepare(). > > > > > > > > > > > > > > > > Well, I'm not sure about that. Let me consider that for a > > > > > > > > while. > > > > > > > OK. let me be more clear about the situation i see in USB. > > > > > > > Correct me if I am wrong, a USB device will always has at > > > > > > > least one endpoint/ep_00 as a kid for control pipe, it is a > > > > > > > logical device. So when device_prepare() is called, its > > > > > > > call back is NULL which makes .direct_complete = 0. Since > > > > > > > children device suspend is called before parents, the > > > > > > > parents .direct_complete flag will always get cleared. > > > > > > > > > > > > > > What i am trying to achieve here is to see if we avoid > > > > > > > resuming built-in (hardwired connect_type) non-hub USB > > > > > > > devices based on this new patchset. E.g. we don't want to > > > > > > > resume/suspend USB camera every time in system > > > > > > > suspend/resume cycle if they are already rpm suspended. We > > > > > > > can save ~100ms resume time for the devices we have tested. > > > > > > > > > > > > This is a good point, but I don't think it is at all related > > > > > > to ignore_children. > > > > > > > > > > > > Instead, it seems that the best way to solve it would be to > > > > > > add a ->prepare() handler for usb_ep_device_type that would > > > > > > always turn on direct_complete. > > > > > > > > > > > yeah, that would solve the problem with EP device type. But what > > > > > about other subdevices. e.g. for USB camera, uvcvideo device? We > > > > > can add .prepare(return 1;) for each level but would it be > > > > > better to have a flag similar to ignore_children if not > > > > > ignore_children itself. > > > > > > > > Something like that could always be added. > > > or, how about if a device's .prepare() is NULL, we could > > > assume .direct_resume() should be set. i.e. > > > > You mean direct_complete (which is a flag, not a function), I suppose? > > > yes. > > Wouldn't that go a bit too far? It seems to be based on the > > assumption that all devices having no ->prepare() callback can be > > safely left in runtime suspend over a system suspend/resume cycle, > > but is that assumption actually satisfied for all such devices? > > > yes, I agree it is risky though i don't see problems with my limited > testing. But on the other side, it is too strict. > I also tried adding .prepare( return 1;) to usb_ep_device_type pm ops, > that didn't work either. The reason is that ep devices don't support > runtime pm (disable_depth > 0). I think in this case ignore_children > flag should be the right indicator to ignore pm_runtime_suspended()? I guess an "ignore this device completely for PM" flag as suggested by Alan would be better. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -1539,7 +1539,7 @@ static int device_prepare(struct device *dev, pm_message_t state) pm_runtime_put(dev); return ret; } - dev->power.direct_complete = ret > 0 && state.event == PM_EVENT_SUSPEND + dev->power.direct_complete = (!callback || ret > 0) && state.event == PM_EVENT_SUSPEND && pm_runtime_suspended(dev); dev_dbg(dev, "%s:direct_complete %d, info %s\n", __func__,