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:	Tue, 7 Aug 2007 13:30:20 +0900
From:	"Joonwoo Park" <joonwpark81@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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,
	linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [PATCH] kexec: fix pci device initialization fail after kexec (2.6.23-rc2). (Related to e1000 doesn't resume properly from standby)

2007/8/7, Rafael J. Wysocki <rjw@...k.pl>:
> On Monday, 6 August 2007 17:50, 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.
>
> Section 5.4.1 of PCI PM 1.1. spec is about D3_hot.  Specifically, it says
> that if a device in D3_hot is programmed to D0, it performs the equivalent of
> a warm reset.  IOW, this is supposed to happen if the current state is D3_hot
> and the targed state is D0, which is covered by the code snippet above.

IMHO, it is seems to the spec says just *programmed  to D0* not
*programmed from D3hot to D0*.
Actually, I got current_state UNKNOWN and state PCI_D0 after kexec's
start new kernel with dual port 82546EB fiber ethernet card.

>
> Greetings,
> Rafael
>
>
> --
> "Premature optimization is the root of all evil." - Donald Knuth
>

Simon, this patch was checked with checkpatch.pl and fixed some fault.

Signed-off-by: Joonwoo Park <joonwpark81@...il.com>

---
 drivers/pci/pci.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 37c00f6..0f086d9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -467,7 +467,8 @@ pci_set_power_state(struct pci_dev *dev, pci_power_t state)

 	/* Mandatory power management transition delays */
 	/* see PCI PM 1.1 5.6.1 table 18 */
-	if (state == PCI_D3hot || dev->current_state == PCI_D3hot)
+	if (state == PCI_D3hot || dev->current_state == PCI_D3hot ||
+	    state == PCI_D0)
 		msleep(pci_pm_d3_delay);
 	else if (state == PCI_D2 || dev->current_state == PCI_D2)
 		udelay(200);
-


Best regards,
Joonwoo Park.
-
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