Hi Sarah, I will resubmit the patch with these changes shortly. On Fri, Aug 9, 2013 at 10:22 AM, Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> wrote: > Hi Shawn, > > I noticed that the ChromeOS kernel tree is still using this particular > patch, and thought it was probably time to revisit it. > > On Sat, May 25, 2013 at 09:57:57AM -0700, Shawn Nematbakhsh wrote: >> Hi Sarah and Alan, >> >> Thanks for the comments. I will make the following revisions: >> >> 1. Call pm_runtime_get_noresume only when the first device is connected, >> and call pm_runtime_put when the last device is disconnected. >> 2. Wrap the calls in an ifdef CONFIG_USB_DEFAULT_PERSIST. >> 3. Make sure that all pm_runtime_get_noresume calls have a corresponding >> pm_runtime_put somewhere (originally the intent was to disable runtime >> suspend "forever", but no longer). >> >> In principle, would the patch be acceptable with these revisions? > > The thread petered off with all other options turning out to be > dead-ends, so yes, if you made those changes, you could get that patch > upstream. I would like the ChromeOS kernel to be as close to upstream > as possible, so please resubmit this patch with those changes. > > Thanks, > Sarah Sharp > >> >> On Sat, May 25, 2013 at 7:11 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>wrote: >> >> > On Fri, 24 May 2013, Sarah Sharp wrote: >> > >> > > On Fri, May 24, 2013 at 11:12:57AM -0700, Shawn Nematbakhsh wrote: >> > > > If a USB controller with XHCI_RESET_ON_RESUME goes to runtime suspend, >> > > > a reset will be performed upon runtime resume. Any previously suspended >> > > > devices attached to the controller will be re-enumerated at this time. >> > > > This will cause problems, for example, if an open system call on the >> > > > device triggered the resume (the open call will fail). >> > > >> > > That's ugly, but disabling runtime PM is going to have a big impact on >> > > the power consumption of those systems. >> > > >> > > Alan, do you think this is really the right thing to be doing here? It >> > > feels like userspace should just be able to deal with devices >> > > disconnecting on resume. After all, there are lots of USB devices that >> > > can't handle USB device suspend at all. >> > >> > This is a complicated issue. It depends on the runtime PM settings for >> > both the device and the host controller. >> > >> > As just one aspect, consider the fact that if it wants to, userspace >> > can already prevent the controller from going into runtime suspend. >> > Always preventing this at the kernel level, even when no devices are >> > plugged in, does seem too heavy-handed. >> > >> > > Shouldn't userspace just disable runtime PM for the USB device classes >> > > that don't have a reset resume callback? >> > >> > That's not so easy, because the kernel changes over time. Userspace >> > has no general way to tell which drivers have reset-resume support. >> > >> > > > Note that this change is only relevant when persist_enabled is not set >> > > > for USB devices. >> > > >> > > Could we at least wrap the call in an ifdef CONFIG_USB_DEFAULT_PERSIST? >> > > That way if people have USB persist turned off in their configuration, >> > > their host will still be able to suspend. >> > >> > Not just that; the patch is incorrect on the face of it... >> > >> > > > @@ -4687,6 +4687,12 @@ int xhci_gen_setup(struct usb_hcd *hcd, >> > xhci_get_quirks_t get_quirks) >> > > > >> > > > get_quirks(dev, xhci); >> > > > >> > > > + /* If we are resetting upon resume, we must disable runtime PM. >> > > > + * Otherwise, an open() syscall to a device on our runtime >> > suspended >> > > > + * controller will trigger controller reset and device >> > re-enumeration */ >> > > > + if (xhci->quirks & XHCI_RESET_ON_RESUME) >> > > > + pm_runtime_get_noresume(dev); >> > > > + >> > >> > It adds a pm_runtime_get call with no corresponding pm_runtime_put. >> > >> > Alan Stern >> > >> > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
