Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759668Ab2JLPIT (ORCPT ); Fri, 12 Oct 2012 11:08:19 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:52736 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759059Ab2JLPIQ (ORCPT ); Fri, 12 Oct 2012 11:08:16 -0400 MIME-Version: 1.0 X-Originating-IP: [121.6.200.239] In-Reply-To: References: Date: Fri, 12 Oct 2012 23:08:14 +0800 Message-ID: Subject: Re: [3.6-rc7] switcheroo race with Intel HDA... From: Daniel J Blueman To: Takashi Iwai Cc: Dave Airlie , Linux Kernel , alsa-devel@alsa-project.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4947 Lines: 115 On 10 October 2012 20:34, Takashi Iwai wrote: > At Tue, 9 Oct 2012 22:26:40 +0800, > Daniel J Blueman wrote: >> On 9 October 2012 21:04, Takashi Iwai wrote: >> > At Tue, 9 Oct 2012 19:23:56 +0800, >> > Daniel J Blueman wrote: >> >> On 9 October 2012 18:07, Takashi Iwai wrote: >> >> > 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 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. >> >> [...] >> >> >> >> hda-intel: 0000:01:00.1: spurious response 0x0:0x0, last cmd=0x1f0004 >> >> $ lspci -s :1:0.1 >> >> 01:00.1 Audio device: NVIDIA Corporation Device 0e1b (rev ff) >> >> >> >> It's the NVIDIA device which presumably hasn't completed it's >> >> transition to D3 at the time the OFF is executed. >> > >> > OK, then could you try the patch below on the top of previous two >> > patches? >> >> The first IGD switcheroo command fails to switch to the integrated GPU: >> >> # cat /sys/kernel/debug/vgaswitcheroo/switch >> 0:DIS:+:Pwr:0000:01:00.0 >> 1:IGD: :Pwr:0000:00:02.0 >> 2:DIS-Audio: :Pwr:0000:01:00.1 >> # echo IGD >/sys/kernel/debug/vgaswitcheroo/switch >> vga_switcheroo: client 1 refused switch >> >> I also instrumented snd_hda_lock_devices, but none of the failure >> paths are being taken, which would leave inconsistent state, as the >> return value isn't checked. > > Hm, right, the return value of snd_hda_lock_devices() isn't checked, > but I don't understand how this results like above. > Basically switching is protected by mutex in vga_switcheroo.c, so the > whole operation in the client side should be serialized. > > In anyway, try the patch below cleanly, and see the spurious message > error coming up at which timing. [...] The patch _does_ address the issue. A recent update to my Macbook firmware misleadingly broke i915 switching, but since I can reproduce the oops without the IGD switching completing with the stock kernel, and consistently can't without [1], the patch is good. Tested-by: Daniel J Blueman Thanks Takashi! Daniel --- [1] snd_hda_intel 0000:00:1b.0: enabling device (0000 -> 0002) snd_hda_intel 0000:00:1b.0: irq 54 for MSI/MSI-X XXX 0000:00:1b.0: azx_codec_create entered vga_switcheroo: enabled XXX 0000:00:1b.0: azx_codec_create done input: HDA Intel PCH Headphone as /devices/pci0000:00/0000:00:1b.0/sound/card0/input9 snd_hda_intel 0000:01:00.1: enabling device (0000 -> 0002) hda_intel: Disabling MSI hda-intel: 0000:01:00.1: Handle VGA-switcheroo audio client XXX 0000:01:00.1: azx_codec_create entered XXX 0000:01:00.1: azx_codec_create done input: HDA NVidia HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:01.0/0000:01:00.1/sound/card1/input12 input: HDA NVidia HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:01.0/0000:01:00.1/sound/card1/input13 input: HDA NVidia HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:01.0/0000:01:00.1/sound/card1/input14 vga_switcheroo: client 1 refused switch i915: switched off -- Daniel J Blueman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/