linux-kernel - Re: PME_Turn

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Date:	Wed, 17 Jan 2007 14:55:48 -0800
From:	Greg KH <greg@...ah.com>
To:	"Miller, Mike (OS Dev)" <Mike.Miller@...com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Nguyen, Tom L" <tom.l.nguyen@...el.com>,
	"Brainard, Jim" <jim.brainard@...com>,
	"Patterson, Andrew D (Linux R&D)" <andrew.patterson@...com>,
	linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: PME_Turn_Off in Linux

On Wed, Jan 17, 2007 at 04:35:02PM -0600, Miller, Mike (OS Dev) wrote:
> > On Wed, Jan 17, 2007 at 10:43:14AM -0600, Miller, Mike (OS Dev) wrote:
> > > Hello,
> > > We've been seeing some nasty data corruption issues on some 
> > platforms.
> > > We've been capturing PCI-E traces looking for something 
> > nasty but we 
> > > haven't found anything yet. One of the hardware guys if asking if 
> > > there is a call in Linux to issue a PME_Turn_Off broadcast message.
> > >  
> > > PME_Turn_Off Broadcast Message
> > > Before main component power and reference clocks are turned 
> > off, the 
> > > Root Complex or Switch Downstream Port must issue a 
> > broadcast Message 
> > > that instructs all agents downstream of that point within the 
> > > hierarchy to cease initiation of any subsequent PM_PME Messages, 
> > > effective immediately upon receipt of the PME_Turn_Off Message.
> > > 
> > > This must be initiated from the root complex. Is there such 
> > a call in 
> > > linux?
> > 
> > This firmware that implements the PCI-E connection should do 
> > this, I don't think there is anything that the Operating 
> > system can do to control this, as PCI-E should be transparant 
> > to the OS.
> 
> Hmmm, the hw folks tell me that "other" os'es implement that. But I
> would tend to agree that system firmware should probably be doing this.

Where would the "other" oses implement this, as they don't even know the
pci device is a pci-e port?  How can the os send a PCI-E message without
talking directly to the chipset-specific controller chip?

> > 
> > Unless this is on a PCI-E Hotplug system?  What is the 
> 
> No hotplug.

That's good :)

> > sequence of events that cause the data corruption?
> 
> Install rhel4 u4 on ia64, at the reboot prompt let the system sit idle
> for several hours or overnight. Then after rebooting the filesystems are
> totally trashed. I usually get a message that the kernel is not a valid
> compressed file format. If I try to rescue the system I cannot mount any
> filesystems. I don't have the message handy but it complains about an
> invalid Verneed record, whatever that is.

The RHEL4 kernel is pretty old as far as PCI-E goes.  Can you try this
on a kernel.org release?  2.6.19.2 would be great at the least.  If not,
you're going to have to get your support from Red Hat on this issue :(

Any kernel log messages while the machine is idle before rebooting?

What tasks are running overnight that would cause writes to the disk?

thanks,

greg k-h
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