From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com ([209.85.212.177]:36174 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751579AbbE0Ffr (ORCPT ); Wed, 27 May 2015 01:35:47 -0400 Received: by wizk4 with SMTP id k4so98733240wiz.1 for ; Tue, 26 May 2015 22:35:46 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150527044749.GB21644@fury.dvhart.com> References: <20150223215155.18444386@neptune.home> <20150303172753.GF83894@vmdeb7> <20150305232038.1873d380@neptune.home> <20150306174254.GB19001@vmdeb7> <20150307011546.0050279d@neptune.home> <20150309225238.0b9ced4e@neptune.home> <20150311223445.6af76f7c@neptune.home> <20150527044749.GB21644@fury.dvhart.com> Date: Tue, 26 May 2015 22:35:46 -0700 Message-ID: Subject: Re: [Patch v3] apple-gmux: lock iGP IO to protect from vgaarb changes From: Michael Marineau To: Darren Hart Cc: =?UTF-8?Q?Bruno_Pr=C3=A9mont?= , Bjorn Helgaas , platform-driver-x86@vger.kernel.org, "linux-kernel@vger.kernel.org" , Petri Hodju , Matthew Garrett , "linux-pci@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, May 26, 2015 at 9:47 PM, Darren Hart wrote: > On Tue, May 26, 2015 at 12:10:48PM -0700, Michael Marineau wrote: >> FYI, this actually broke backlight controls on my MBP11,3 because the >> assumption the patch makes that gmux is always loaded before graphics >> drivers didn't hold true. At least for me dracut included the nouveau >> module in the initrd but not gmux, ensuring the ordering was wrong. No >> errors were reporting, and gmux still offered the backlight device, it >> just became inoperable. I worked around this for my kernel by building >> gmux into vmlinuz instead of as a module but that isn't going to in >> more general configs because there is an apple backlight driver which >> cannot be built at all in that configuration. >> > > Thank you for reporting this Michael, > > That is tough as nouveau doesn't have an explicit dependency on gmux, so we > could do something like a passive request_module(), but if it isn't in the > initrd image, it would still fail as you describe. > >> Is there a way to make the ordering between nouveau and gmux more >> explicit/reliable? Can gmux complain loudly if the ordering is ever >> wrong? > > It should print an error if the probe fails due to the IO already being in use > or if it can't be allocated. The disabled IO case is only info level though, > perhaps that should be higher priority. Printing something when failing to probe > seems like a reasonable thing to do. > > Michael, which message do you get if you boot with "debug" or "loglevel=6" when > apple-gmux is not built-in? No error, gmux claims it worked: [ 13.693379] apple_gmux: Found gmux version 4.0.8 [indexed] [ 13.693400] vgaarb: device changed decodes: PCI:0000:01:00.0,olddecodes=io+mem,decodes=io+mem:owns=none [ 13.693404] apple_gmux: locked IO for PCI:0000:01:00.0 Full dmesg: https://gist.github.com/marineam/0e5a23548e8b3b2e1d50