Messages in this thread | | | Date | Tue, 20 Nov 2012 11:04:35 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH] PCI/PM: Keep runtime PM enabled for unbound PCI devices |
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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 <stern@rowland.harvard.edu>
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