From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754169AbbCNDT4 (ORCPT ); Fri, 13 Mar 2015 23:19:56 -0400 Received: from mail-ob0-f171.google.com ([209.85.214.171]:33139 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793AbbCNDTw (ORCPT ); Fri, 13 Mar 2015 23:19:52 -0400 MIME-Version: 1.0 X-Originating-IP: [76.119.162.148] Date: Fri, 13 Mar 2015 23:19:51 -0400 Message-ID: Subject: Commit 0e32b39c ("drm/i915: add DP 1.2 MST support (v0.7)") breaking DP audio on T440s From: Paul Moore To: Dave Airlie , intel-gfx@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ever since v3.17 I've had a problem with displayport audio on my system, but until lately I haven't had a chance to bisect the problem. After a few rounds I've isolated the buggy commit to 0e32b39c ("drm/i915: add DP 1.2 MST support (v0.7)"). Simply put, prior to v3.17 everything worked correctly: audio from my system was routed to my monitor via the DP connection and finally out to the speakers connected to the monitor. However, starting with kernel v3.17 this no longer works. The various PulseAudio tools all indicate that the HDMI/DP audio output is unplugged/not-available. I've tried a few different xrandr commands found via google and manpages but nothing short of reverting to v3.16 solves the problem. I'm hoping that someone with more understanding of the Intel graphics drivers will be able to make some sense of it all and provide a fix. I'm more than happy to provide additional information and test any patches you may have. For reference, my system is a ThinkPad T440s with a "Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b)" (according to lspci) connected to a Dell U3011 via a Gefen DP KVM. -Paul -- paul moore www.paul-moore.com