Re: [PATCH] PCI / PM: Disable wakeup during shutdown for devices not enabled to wake up

[Jesse Barnes <jbarnes@virtuousgeek.org>]

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On Fri, 2 Mar 2012 15:44:27 +0100
Francois Romieu <romieu@fr.zoreil.com> wrote:

> Rafael J. Wysocki <rjw@sisk.pl> :
> [...]
> > If a PCI device is enabled to generate wakeup signals (PME) when put
> > into a low-power state by runtime PM, it will be still enabled to
> > generate those signals after the system shutdown, unless its driver's
> > .shutdown() callback takes care of the wakeup signals generation
> > setting.  Moreover, there are devices that are not enabled to wake
> > up the system and that are configured by runtime PM to generate
> > wakeup signals so that (runtime) remote wakeup works with them.
> > Those devices should be reconfigured during system shutdown so that
> > they don't generate wakeup signals, but at least some drivers don't
> > do that.  However, that very well may be done by the PCI core so
> > that drivers don't have to worry about it.  For this reason, modify
> > pci_device_shutdown() to disable the generation of wakeup events for
> > devices not supposed to wake up the system.
> 
> On a tangent side, if register writes are ignored by the PCI device
> after its .runtime_suspend() handler has been called, whose
> responsibility is it to bring back the device in a state from where
> the .shutdown() callback can operate ?
> 
> The r8169 driver exhibits this problem. Its .runtime_xyz() callbacks
> are called on link activity. Thus, after a link loss - or no link at
> all - .runtime_suspend() and an ineffective .shutdown(), the device is
> brought back up as soon as the link recovers.
> 
> The device driver can monitor .runtime_{suspend / resume} activity
> and take appropriate action in .shutdown(). Sameer Nanda has sent
> such a patch (see below). I am not sure this is the adequate fix:
> 1. the driver ought essentially to perform the hardware part of a
>    .runtime_resume() on its own behalf. Mildly engaging.
> 2. by the same line as above, could it make more sense to call
>    pm_runtime_resume() in driver/base/core.c::device_shutdown ?

I thought there would be a more elegant way of increasing the device
use count on entering .shutdown, either from the wifi core or at the
driver level, so you don't have to track things with a separate flag.

Rafael?

-- 
Jesse Barnes, Intel Open Source Technology Center

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