linux-kernel - Re: pci commands resume order [Was: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff]

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Date:	Fri, 25 Apr 2008 10:11:51 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	linux-pci@...ey.karlin.mff.cuni.cz
Cc:	Jiri Slaby <jirislaby@...il.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: pci commands resume order [Was: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff]

On Friday, April 25, 2008 1:18 am Jiri Slaby wrote:
> On 04/25/2008 09:45 AM, David Miller wrote:
> > I notice Jiri, in your hardware list, you have an ath5k Atheros AR5212
> > chip in there.
> >
> > I took a look at the resume code for ath5k but nothing really suspicious
> > there except:
> >
> > 	err = pci_enable_device(pdev);
> > 	if (err)
> > 		return err;
> >
> > 	pci_restore_state(pdev);
> >
> > Shouldn't we restore state before we turn the chip back on and thus
> > potentially let it start DMA'ing all over the place?
>
> Hmm, actually every second wireless driver do this :/. I think it's wrong
> too. Jesse?

It might be a little safer to enable the device after restoring its state, but 
if your device starts DMAing randomly when going from D3->D0 it's probably 
not a very good device. :)

> BTW pci_set_power_state(pdev, PCI_D0); in resume isn't needed at all,
> right? It's done in pci_enable_device, isn't it?

Right, pci_enable_device will put the device in D0, so setting it again is 
redundant (looks like lots of drivers do this).

Jesse
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