linux-kernel - Re: [PATCH v2 6/7] PCI/PM: warn about incomplete actions in ->runtime

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Date:	Tue, 05 Feb 2013 00:57:59 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	e1000-devel@...ts.sourceforge.net, linux-pci@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 6/7] PCI/PM: warn about incomplete actions in ->runtime_suspend()
 callback

Rafael J. Wysocki wrote:
> On Monday, February 04, 2013 03:56:12 PM Konstantin Khlebnikov wrote:
>> Documentation/power/pci.txt says:
>> | It is expected that the device driver's pm->runtime_suspend() callback will
>> | not attempt to prepare the device for signaling wakeup or to put it into a
>> | low-power state.  The driver ought to leave these tasks to the PCI subsystem
>> | that has all of the information necessary to perform them.
>>
>> After commit 42eca2302146fed51335b95128e949ee6f54478f
>> ("PCI: Don't touch card regs after runtime suspend D3")
>> | If the driver takes care of state saving, don't touch any registers on it.
>> pci_pm_runtime_suspend() thinks if state has been saved by ->runtime_suspend()
>> that means device alredy prepared for wakeup and probably no longer accessible.
>>
>> Thus driver must either do all actions or leave all these tasks to PCI subsystem.
>
> I don't like this one, because it will generate noise for drivers that
> legitimately use pci_save_state() in their runtime suspend callbacks
> and know what they are doing.

Ok, you're right. Both these warnings can be false-positive.
For example some of wifi cards easily might be weird enough for this.

>
> Thanks,
> Rafael
>
>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>> Cc: Rafael J. Wysocki<rafael.j.wysocki@...el.com>
>> Cc: Bjorn Helgaas<bhelgaas@...gle.com>
>> Cc: linux-pci@...r.kernel.org
>> ---
>>   drivers/pci/pci-driver.c |   15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
>> index f9aa311..2b0ff9a 100644
>> --- a/drivers/pci/pci-driver.c
>> +++ b/drivers/pci/pci-driver.c
>> @@ -1009,12 +1009,19 @@ static int pci_pm_runtime_suspend(struct device *dev)
>>   		return 0;
>>   	}
>>
>> -	if (!pci_dev->state_saved) {
>> -		pci_save_state(pci_dev);
>> -		pci_finish_runtime_suspend(pci_dev);
>> +	if (pci_dev->state_saved) {
>> +		WARN_ONCE(pci_dev->current_state == prev,
>> +			"PCI PM: Power state of device not changed by %pF\n",
>> +			pm->runtime_suspend);
>> +		WARN_ONCE(pci_dev_run_wake(pci_dev)&&
>> +				!pci_dev->wakeup_prepared,
>> +			"PCI PM: Waking of device not configured by %pF\n",
>> +			pm->runtime_suspend);
>> +		return 0;
>>   	}
>>
>> -	return 0;
>> +	pci_save_state(pci_dev);
>> +	return pci_finish_runtime_suspend(pci_dev);
>>   }
>>
>>   static int pci_pm_runtime_resume(struct device *dev)
>>
>> --
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