On Wednesday, November 28, 2012 03:25:59 PM Bjorn Helgaas wrote: > On Tue, Nov 20, 2012 at 1:08 AM, Huang Ying <ying.huang@xxxxxxxxx> wrote: > > For unbound PCI devices, what we need is: > > > > - Always in D0 state, because some devices does not work again after > > being put into D3 by the PCI bus. > > > > - In SUSPENDED state if allowed, so that the parent devices can still > > be put into low power state. > > > > To satisfy these requirement, the runtime PM for the unbound PCI > > devices are disabled and set to SUSPENDED state. One issue of this > > solution is that the PCI devices will be put into SUSPENDED state even > > if the SUSPENDED state is forbidden via the sysfs interface > > (.../power/control) of the device. This is not an issue for most > > devices, because most PCI devices are not used at all if unbounded. > > But there are exceptions. For example, unbound VGA card can be used > > for display, but suspend its parents make it stop working. > > > > To fix the issue, we keep the runtime PM enabled when the PCI devices > > are unbound. But the runtime PM callbacks will do nothing if the PCI > > devices are unbound. This way, we can put the PCI devices into > > SUSPENDED state without put the PCI devices into D3 state. > > Does this fix a reported problem? Is there a bug report URL? What > problem would a user notice? There is a BZ: https://bugzilla.kernel.org/show_bug.cgi?id=48201 Unfortunately, the reporter hasn't confirmed that the bug is fixed, although we're quite confident that it will be. > This doesn't look critical enough to try to put in v3.7 (correct me if > I'm wrong). It's getting pretty late for the v3.8 merge window, but > it looks like it qualifies as a bug fix that we would merge even after > the merge window, so I'll put it in my -next branch headed for v3.8. > Then it can be backported to v3.6 and v3.7. I think that's OK. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
