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, 6 Aug 2007 16:50:15 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Joonwoo Park" <joonwpark81@...il.com>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Simon Arlott" <simon@...e.lp0.eu>, "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 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);

> 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.

>     pci_restore_bars(dev);
> + }
> 
>   return 0;
>  }

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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