Re: [PATCH] PCI/PM: Keep runtime PM enabled for unbound PCI devices
From: Bjorn Helgaas
Date: Tue Dec 04 2012 - 19:06:47 EST
On Wed, Nov 28, 2012 at 3:43 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> 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
I added the BZ link and put this in my -next branch. Thanks!
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