linux-kernel - Re: [3.6-rc7] switcheroo race with Intel HDA...

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Message-ID: <s5hr4p8ez6u.wl%tiwai@suse.de>
Date:	Tue, 09 Oct 2012 12:07:21 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Daniel J Blueman <daniel@...ra.org>
Cc:	Dave Airlie <airlied@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	alsa-devel@...a-project.org
Subject: Re: [3.6-rc7] switcheroo race with Intel HDA...

At Tue, 09 Oct 2012 12:04:08 +0200,
Takashi Iwai wrote:
> 
> At Tue, 9 Oct 2012 00:34:09 +0800,
> Daniel J Blueman wrote:
> > 
> > On 8 October 2012 20:58, Takashi Iwai <tiwai@...e.de> wrote:
> > > At Tue, 25 Sep 2012 13:20:05 +0800,
> > > Daniel J Blueman wrote:
> > >> On my Macbook with a discrete Nvidia GPU, there is a race between
> > >> selecting the integrated GPU and putting the discrete GPU into D3 [1],
> > >> reliably causing a kernel oops [2].
> > >>
> > >> Introducing a delay of ~1s between the calls prevents this. When the
> > >> second 'OFF' write path executes, it looks like struct azx at
> > >> card->private_data hasn't yet been allocated yet [3], so there is
> > >> likely some locking missing.
> > >
> > > It's rather pci_get_drvdata() returning NULL (i.e. card is NULL, thus
> > > card->private_data causes Oops).  Could you check the patch like below
> > > and see whether you get a kernel warning (but no Oops) or the problem
> > > gets fixed by shifting the assignment of pci drvdata?
> > [...]
> > 
> > Good patching. Calling pci_set_drvdata later prevents the oops in HDA,
> > though we see unexpected 0x0 responses in the response ring buffer
> > [1], which we don't see when there's a >~1.5s delay between IGD and
> > OFF.
> 
> If the previous patch fixed, it means that the switching occurred
> during the device was being probed.  Maybe a better approach to
> register the VGA switcheroo after the proper initialization.
> 
> The patch below is a revised one.  Please give it a try.

Also, it's not clear which card spews the spurious response.
Apply the patch below in addition.


thanks,

Takashi

---
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index f09ff6c..9a0a29d 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -829,8 +829,9 @@ static void azx_update_rirb(struct azx *chip)
 			smp_wmb();
 			chip->rirb.cmds[addr]--;
 		} else
-			snd_printk(KERN_ERR SFX "spurious response %#x:%#x, "
+			snd_printk(KERN_ERR SFX "%s: spurious response %#x:%#x, "
 				   "last cmd=%#08x\n",
+				   pci_name(chip->pci),
 				   res, res_ex,
 				   chip->last_cmd[addr]);
 	}
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