From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751087AbeDNLZc (ORCPT ); Sat, 14 Apr 2018 07:25:32 -0400 Received: from bmailout3.hostsharing.net ([176.9.242.62]:51283 "EHLO bmailout3.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750936AbeDNLZb (ORCPT ); Sat, 14 Apr 2018 07:25:31 -0400 Date: Sat, 14 Apr 2018 13:25:29 +0200 From: Lukas Wunner To: Kai-Heng Feng Cc: Takashi Iwai , mario.limonciello@dell.com, pali.rohar@gmail.com, andy@infradead.org, dvhart@infradead.org, mjg59@srcf.ucam.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org Subject: Re: [PATCH v3 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics Message-ID: <20180414112529.GB4245@wunner.de> References: <20180412104239.25584-1-kai.heng.feng@canonical.com> <20180412104239.25584-3-kai.heng.feng@canonical.com> <018FF40E-B380-4E22-9599-2F4A2A8B51B7@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <018FF40E-B380-4E22-9599-2F4A2A8B51B7@canonical.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 12, 2018 at 10:12:49PM +0800, Kai-Heng Feng wrote: > at 6:50 PM, Takashi Iwai wrote: > > On Thu, 12 Apr 2018 12:42:39 +0200, Kai-Heng Feng wrote: > > > When SG is enabled, the unused AMD audio controller still exposes its > > > sysfs, so userspace still opens the control file and stream. If > > > userspace tries to output sound through the stream, it hangs when > > > runtime suspend kicks in: > > > [ 12.796265] snd_hda_intel 0000:01:00.1: Disabling via vga_switcheroo > > > [ 12.796367] snd_hda_intel 0000:01:00.1: Cannot lock devices! > > > > > > Since the discrete audio controller isn't useful when SG enabled, we > > > should just disable the device. > > > > > > Signed-off-by: Kai-Heng Feng > > > > I thought we manage this better now with runtime PM by Lukas's recent > > patchset? > > Yes, that's true. I'll update commit log for next iteration. > > Nevertheless, the unusable control file and stream still get exposed via > sysfs. > We should disable them when SG is enabled. Right, the hang on runtime suspend as mentioned in the commit message should be gone in 4.17. The purpose of this patch is thus to prevent the user from seeing or opening the HDA controller on the discrete GPU. If SG is enabled, external DP/HDMI displays are muxed to the Intel GPU, hence the HDA controller on the discrete GPU cannot communicate with the attached displays. Thanks, Lukas