linux-kernel - Re: [PATCH] PCI / PM: Fix fallback to PCI_D0 in pci_platform_power

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Date:	Mon, 15 Apr 2013 14:18:18 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	"Benenati, Chris J" <chris.j.benenati@...el.com>,
	Ajaykumar Hotchandani <ajaykumar.hotchandani@...cle.com>
Subject: Re: [PATCH] PCI / PM: Fix fallback to PCI_D0 in pci_platform_power_transition()

On Fri, Apr 12, 2013 at 11:50 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Fri, Apr 12, 2013 at 4:58 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> Commit b51306c (PCI: Set device power state to PCI_D0 for device
>> without native PM support) modified pci_platform_power_transition()
>> by adding code causing dev->current_state for devices that don't
>> support native PCI PM but are power-manageable by the platform to be
>> changed to PCI_D0 regardless of the value returned by the preceding
>> platform_pci_set_power_state().  In particular, that also is done
>> if the platform_pci_set_power_state() has been successful, which
>> causes the correct power state of the device set by
>> pci_update_current_state() in that case to be overwritten by PCI_D0.
>>
>> Fix that mistake by making the fallback to PCI_D0 only happen if
>> the platform_pci_set_power_state() has returned an error.
>>
>> Reported-by: Chris J. Benenati <chris.j.benenati@...el.com>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> Cc: <stable@...r.kernel.org>

I folded in Yinghai's simplification and added a URL to Chris's report
and applied to my pci/rafael-pm branch:
http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/log/?h=pci/rafael-pm

If it still looks good to you, Rafael, I'll merge it to next for v3.10.

I don't know what the user-visible effect of this is, and it's been
around for a long time, but if you think this should go in v3.9
instead, let me know.

Bjorn

>> ---
>>  drivers/pci/pci.c |    3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> Index: linux-pm/drivers/pci/pci.c
>> ===================================================================
>> --- linux-pm.orig/drivers/pci/pci.c
>> +++ linux-pm/drivers/pci/pci.c
>> @@ -646,8 +646,7 @@ static int pci_platform_power_transition
>>                 error = platform_pci_set_power_state(dev, state);
>>                 if (!error)
>>                         pci_update_current_state(dev, state);
>> -               /* Fall back to PCI_D0 if native PM is not supported */
>> -               if (!dev->pm_cap)
>> +               else if (!dev->pm_cap) /* Fall back to PCI_D0 */
>>                         dev->current_state = PCI_D0;
>>         } else {
>>                 error = -ENODEV;
>>
>
> Acked-by: Yinghai Lu <yinghai@...nel.org>
>
> also could simplify it further.
>
> ---
>  drivers/pci/pci.c |   12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>
> Index: linux-2.6/drivers/pci/pci.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/pci.c
> +++ linux-2.6/drivers/pci/pci.c
> @@ -646,15 +646,11 @@ static int pci_platform_power_transition
>          error = platform_pci_set_power_state(dev, state);
>          if (!error)
>              pci_update_current_state(dev, state);
> -        /* Fall back to PCI_D0 if native PM is not supported */
> -        if (!dev->pm_cap)
> -            dev->current_state = PCI_D0;
> -    } else {
> +    } else
>          error = -ENODEV;
> -        /* Fall back to PCI_D0 if native PM is not supported */
> -        if (!dev->pm_cap)
> -            dev->current_state = PCI_D0;
> -    }
> +
> +    if (error && !dev->pm_cap) /* Fall back to PCI_D0 */
> +        dev->current_state = PCI_D0;
>
>      return error;
>  }
--
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