linux-kernel - Re: [PATCH] ACPI / PM: Take unusual configurations of power resources into account (was: Re: [GIT PATCH] USB patches for 3.9-rc1)

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Date:	Sat, 23 Feb 2013 15:48:59 +0100
From:	Fabio Baltieri <fabio.baltieri@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Dave Jones <davej@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	tianyu.lan@...el.com, linux-acpi@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [PATCH] ACPI / PM: Take unusual configurations of power
 resources into account (was: Re: [GIT PATCH] USB patches for 3.9-rc1)

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: ACPI / PM: Take unusual configurations of power resources into account
> 
> Commit d2e5f0c (ACPI / PCI: Rework the setup and cleanup of device
> wakeup) moved the initial disabling of system wakeup for PCI devices
> into a place where it can actually work and that exposed a hidden old
> issue with crap^Wunusual system designs where the same power
> resources are used for both wakeup power and device power control at
> run time.
> 
> Namely, say there is one power resource such that the ACPI power
> state D0 of a PCI device depends on that power resource (i.e. the
> device is in D0 when that power resource is "on") and it is used
> as a wakeup power resource for the same device.  Then, calling
> acpi_pci_sleep_wake(pci_dev, false) for the device in question will
> cause the reference counter of that power resource to drop to 0,
> which in turn will cause it to be turned off.  As a result, the
> device will go into D3cold at that point, although it should have
> stayed in D0.
> 
> As it turns out, that happens to USB controllers on some laptops
> and USB becomes unusable on those machines as a result, which is
> a major regression from v3.8.
> 
> To fix this problem, (1) increment the reference counters of wakup
> power resources during their initialization if they are "on"
> initially, (2) prevent acpi_disable_wakeup_device_power() from
> decrementing the reference counters of wakeup power resources that
> were not enabled for wakeup power previously, and (3) prevent
> acpi_enable_wakeup_device_power() from incrementing the reference
> counters of wakeup power resources that already are enabled for
> wakeup power.
> 
> In addition to that, if it is impossible to determine the initial
> states of wakeup power resources, avoid enabling wakeup for devices
> whose wakeup power depends on those power resources.
> 
> Reported-by: Dave Jones <davej@...hat.com>
> Reported-by: Fabio Baltieri <fabio.baltieri@...aro.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Works just fine!

Tested-by: Fabio Baltieri <fabio.baltieri@...aro.org>

Thanks,
Fabio

-- 
Fabio Baltieri
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