On Tue, 20 Nov 2012, Huang Ying 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.
Acked-by: Alan Stern <st...@rowland.harvard.edu> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
