On Fri, 16 May 2014 23:08:01 +0200 "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > On Thu, 15 May 2014 10:29:42 -0400 (EDT) > > > > Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > [Jacob Pan] -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
