From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Huang Ying <ying.huang@intel.com>,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [BUGFIX] PM: Fix active child counting when disabled and forbidden
Date: Wed, 07 Nov 2012 17:09:16 +0100 [thread overview]
Message-ID: <2385996.Tx2Do9TUNJ@vostro.rjw.lan> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1211071032070.1859-100000@iolanthe.rowland.org>
On Wednesday, November 07, 2012 10:49:04 AM Alan Stern wrote:
> On Wed, 7 Nov 2012, Huang Ying wrote:
>
> > > > Devices will be disabled if the PCI driver is unbound from the PCI
> > > > device.
> > >
> > > Yes. But without a PCI driver, nothing will call
> > > pm_runtime_set_suspended.
> >
> > pm_runtime_set_suspended will be called in pci_device_remove or error
> > path of local_pci_probe.
>
> Yes, okay. But that's what we want. Unused, driverless PCI devices
> shouldn't force their parents to remain at full power.
>
> > > And even if something does call
> > > pm_runtime_set_suspended, it's still not a problem -- the device can't
> > > be used without a driver.
> >
> > The VGA device can be used without a driver.
>
> Ah, right, that's your _real_ problem. You should have mentioned this
> in the original Changelog for the patch.
>
> Rafael, this does need to be fixed.
Yup.
> The PCI subsystem assumes that
> driverless devices are not in use, so they are disabled for runtime PM
> and marked as suspended. This is not appropriate for VGA devices,
> which can indeed be used without a driver.
>
> I'm not sure what the best solution is. Maybe we should Ying's
> proposal a step farther:
>
> Make pm_runtime_set_suspended() fail if runtime PM is
> forbidden.
>
> Make pm_runtime_forbid() call pm_runtime_set_active()
> (and do a runtime resume of the parent) if disable_depth > 0.
I'd prefer this one. The callers of pm_runtime_forbid() may actually
reasonably expect something like this to happen.
> Make the PCI runtime-idle routine call
> pm_runtime_set_suspended() if disable_depth > 0. Or maybe
> do this for all devices, in the runtime PM core.
That would mean calling it on every call to pm_runtime_put() and friends
which seems to be a bit wasteful.
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
next prev parent reply other threads:[~2012-11-07 16:05 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-05 1:17 [BUGFIX] PM: Fix active child counting when disabled and forbidden Huang Ying
2012-11-05 1:56 ` Alan Stern
2012-11-06 0:43 ` Huang Ying
2012-11-06 15:17 ` Alan Stern
2012-11-07 0:26 ` Huang Ying
2012-11-07 15:49 ` Alan Stern
2012-11-07 16:09 ` Rafael J. Wysocki [this message]
2012-11-07 17:17 ` Alan Stern
2012-11-07 20:21 ` Rafael J. Wysocki
2012-11-07 20:47 ` Alan Stern
2012-11-07 21:44 ` Rafael J. Wysocki
2012-11-07 21:56 ` Alan Stern
2012-11-07 22:51 ` Rafael J. Wysocki
2012-11-07 23:09 ` Rafael J. Wysocki
2012-11-08 1:15 ` Huang Ying
2012-11-08 1:35 ` Rafael J. Wysocki
2012-11-08 2:04 ` Huang Ying
2012-11-08 9:56 ` Rafael J. Wysocki
2012-11-08 17:07 ` Alan Stern
2012-11-09 2:36 ` Huang Ying
2012-11-09 16:41 ` Alan Stern
2012-11-12 0:37 ` Huang Ying
2012-11-12 2:36 ` Alan Stern
2012-11-12 5:55 ` Huang Ying
2012-11-12 16:32 ` Alan Stern
2012-11-13 1:19 ` Huang Ying
2012-11-13 2:32 ` Alan Stern
2012-11-13 5:12 ` Huang Ying
2012-11-13 16:10 ` Alan Stern
2012-11-14 1:08 ` Huang Ying
2012-11-14 9:52 ` Rafael J. Wysocki
2012-11-14 13:35 ` Huang Ying
2012-11-14 16:06 ` Alan Stern
2012-11-13 23:43 ` Rafael J. Wysocki
2012-11-14 10:05 ` Rafael J. Wysocki
2012-11-14 16:42 ` Alan Stern
2012-11-14 19:42 ` Rafael J. Wysocki
2012-11-14 21:45 ` Alan Stern
2012-11-14 23:10 ` Rafael J. Wysocki
2012-11-15 1:03 ` Huang Ying
2012-11-15 9:51 ` Rafael J. Wysocki
2012-11-15 10:09 ` Rafael J. Wysocki
2012-11-15 15:27 ` Alan Stern
2012-11-16 0:36 ` Huang Ying
2012-11-16 0:44 ` Rafael J. Wysocki
2012-11-16 0:48 ` Huang Ying
2012-11-16 0:55 ` Rafael J. Wysocki
2012-11-16 0:54 ` Huang Ying
2012-11-16 1:29 ` Rafael J. Wysocki
2012-11-16 1:27 ` Huang Ying
2012-11-16 10:10 ` Rafael J. Wysocki
2012-11-16 3:11 ` Huang Ying
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