linux-kernel - Re: [PATCH] kexec: fix pci device initialization fail after kexec (2.6.23-rc2). (Related to e1000 doesn't resume properly from standby)

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Date:	Mon, 06 Aug 2007 18:18:15 +0100
From:	Simon Arlott <simon@...e.lp0.eu>
To:	Joonwoo Park <joonwpark81@...il.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>,
	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] kexec: fix pci device initialization fail after kexec
 (2.6.23-rc2). (Related to e1000 doesn't resume properly from standby)

On 06/08/07 16:50, Joonwoo Park wrote:
> 2007/8/6, Rafael J. Wysocki <rjw@...k.pl>:
>> On Monday, 6 August 2007 15:42, Joonwoo Park wrote:
>> > Hi.
>> > I think that the pci_set_power_state() has bug.
>> > The specification says that some delays is required.
>>
>> And they are in place, AFAICS (from drivers/pci/pci.c):
>>
>>        /* Mandatory power management transition delays */
>>        /* see PCI PM 1.1 5.6.1 table 18 */
>>        if (state == PCI_D3hot || dev->current_state == PCI_D3hot)
>>                msleep(pci_pm_d3_delay);
>>        else if (state == PCI_D2 || dev->current_state == PCI_D2)
>>                udelay(200);
>>
> 
> The problem is occurred when state is 'PCI_D0', so those codes can't cover it.
> But pci pm specification 5.4.1 says that when programmed to D0 the
> equivalent of a warm reset, delay for the duration of the D3hot to D0
> Uninitialized state
> transition (10ms) to pci signal drivers remain disabled is required.
> 
>> > Simon, please can I know whether it works to you?
>> > It is seems to the things are related.
>> >
>> > Joonwoo Park.
>> >
>> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> > index 37c00f6..9f78064 100644
>> > --- a/drivers/pci/pci.c
>> > +++ b/drivers/pci/pci.c
>> > @@ -493,8 +493,14 @@ pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>> >    * restore at least the BARs so that the device will be
>> >    * accessible to its driver.
>> >    */
>> > - if (need_restore)
>> > + if (need_restore) {
>> > +   /* The specification also says that "Must ensure that all of
>> > +    * its PCI signal drivers remain disabled for the duration of
>> > +    * the D3hot to D0 Uninitialized state transition".
>> > +    */
>> > +   msleep(10);
>>
>> It's too late for the delay.
>>
> 
> How about this?

It doesn't fix it.

> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 37c00f6..974dd04 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -471,6 +471,8 @@ pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>                 msleep(pci_pm_d3_delay);
>         else if (state == PCI_D2 || dev->current_state == PCI_D2)
>                 udelay(200);
> +      else if (state == PCI_D0)
> +              msleep(10);
> 
>         /*
>          * Give firmware a chance to be called, such as ACPI _PRx, _PSx
> 
> 
>> >     pci_restore_bars(dev);
>> > + }
>> >
>> >   return 0;
>> >  }

Your patches have spaces everywhere instead of tabs.

-- 
Simon Arlott

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