linux-kernel - Re: [PATCH] pci: Don't enable aspm before drivers have had a chance to veto it

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Message-ID: <20100618101506.0c585617@virtuousgeek.org>
Date:	Fri, 18 Jun 2010 10:15:06 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	Matthew Garrett <mjg@...hat.com>,
	Jussi Kivilinna <jussi.kivilinna@...et.fi>,
	"Luis R. Rodriguez" <mcgrof@...badil.infradead.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pci: Don't enable aspm before drivers have had a chance
 to veto it

On Fri, 18 Jun 2010 20:05:42 +0300
Maxim Levitsky <maximlevitsky@...il.com> wrote:

> On Fri, 2010-06-18 at 09:12 -0700, Jesse Barnes wrote: 
> > On Fri, 18 Jun 2010 15:06:51 +0300
> > Maxim Levitsky <maximlevitsky@...il.com> wrote:
> > 
> > > On Wed, 2010-06-09 at 16:05 -0400, Matthew Garrett wrote: 
> > > > The aspm code will currently set the configured aspm policy before drivers
> > > > have had an opportunity to indicate that their hardware doesn't support it.
> > > > Unfortunately, putting some hardware in L0 or L1 can result in the hardware
> > > > no longer responding to any requests, even after aspm is disabled. It makes
> > > > more sense to leave aspm policy at the BIOS defaults at initial setup time,
> > > > reconfiguring it after pci_enable_device() is called. This allows the
> > > > driver to blacklist individual devices beforehand.
> > > > 
> > > > Signed-off-by: Matthew Garrett <mjg@...hat.com>
> > > > ---
> > > 
> > > Hi,
> > > 
> > > I recently discovered that my aspire one wireless troubles (card just
> > > dies after a while) are caused by ASPM L0S state.
> > > The device (AR5001) seems to have a hardware bug, and it also disables
> > > L0S in windows driver.
> > > 
> > > Unfortenuly BIOS (news at 11) enables L0S.
> > > 
> > > Its easy to disable ASPM from driver. It just a matter of calling
> > > pci_disable_link_state.
> > > 
> > > However, that depends on CONFIG_PCIEASPM.
> > > 
> > > How about making pci_disable_link_state always available or even better,
> > > just make CONFIG_PCIEASPM unconditional?
> > 
> > The former is ok with me.  Care to post a patch?
> It not that simple at first glance.
> This functions uses plenty of code from the aspm.c, therefore care
> should be taken to do that properly.
> 
> Of course the easy solution is to compile all code in always, and just
> disable it by runtime switch (it even exists, aspm_disabled)
> Or, another easy solution is to make ath5k depend on CONFIG_PCIEASPM
> 
> What do you think?

So unless a device is *really* broken, it seems like the default policy
should be ok across the board.  So let's get a CONFIG_PCIEASPM removal
patch into the 2.6.36 merge window early to flush out any potential
problems.

-- 
Jesse Barnes, Intel Open Source Technology Center
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