linux-kernel - RE: /sys/module/pcie_aspm/parameters/policy not writable?

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Date:	Wed, 24 Jul 2013 15:19:55 +0000
From:	"Wyborny, Carolyn" <carolyn.wyborny@...el.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>, Pavel Machek <pavel@....cz>
CC:	Greg KH <greg@...ah.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Joe Lawrence <joe.lawrence@...atus.com>,
	Myron Stowe <myron.stowe@...hat.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"Allan, Bruce W" <bruce.w.allan@...el.com>,
	"Skidmore, Donald C" <donald.c.skidmore@...el.com>,
	"Rose, Gregory V" <gregory.v.rose@...el.com>,
	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>,
	"Duyck, Alexander H" <alexander.h.duyck@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"Dave, Tushar N" <tushar.n.dave@...el.com>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>
Subject: RE: /sys/module/pcie_aspm/parameters/policy not writable?

> -----Original Message-----
> From: Bjorn Helgaas [mailto:bhelgaas@...gle.com]
[..}
>
> We *could* consider something like this, since its scope is limited.
> But since the problem also occurs with Windows, it's pretty likely that there's a
> BIOS update to fix it.  I notice on the X60 support page that there are several
> versions newer than what you're running.
> 
> Bjorn

I believe that some BIOS don't allow user control on this feature, thus we end up unable to disable it from driverspace or from userspace, with the method we use today in this scenario.

I have a patch almost ready that attempts to disable using the pci_disable_link_state() call but then checks again to see if its still enabled and if not, then changes the pci config space on the devices on either side of the pcie link.  I plan to send it to this list for Pavel's testing as soon as I have it finished, at worst end of week.

Thanks,

Carolyn

Carolyn Wyborny 
Linux Development 
Networking Division 
Intel Corporation 


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