linux-kernel - PROBLEM: Intel HDMI output busticated on 4.4 (regression)

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Message-ID: <20160119222622.GA16397@draconx.ca>
Date:	Tue, 19 Jan 2016 17:26:22 -0500
From:	Nick Bowler <nbowler@...conx.ca>
To:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Cc:	Sonika Jindal <sonika.jindal@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: PROBLEM: Intel HDMI output busticated on 4.4 (regression)

Hi,

Upgrading from 4.3 to 4.4 breaks my HDMI output on my G45 machine.

As soon as the intel driver is loaded, the monitor shuts off
(standby mode).  Inspecting /sys/class/drm/card0-HDMI-A-1/status
reports "disconnected".  When it is working, this attribute says
"connected".

There is nothing unusual printed to dmesg.

Bisection pinpoints the following:

  237ed86c693d8a8e4db476976aeb30df4deac74b is the first bad commit
  commit 237ed86c693d8a8e4db476976aeb30df4deac74b
  Author: Sonika Jindal <sonika.jindal@...el.com>
  Date:   Tue Sep 15 09:44:20 2015 +0530
  
      drm/i915: Check live status before reading edid
      [...]
      Signed-off-by: Shashank Sharma <shashank.sharma@...el.com>
      Signed-off-by: Sonika Jindal <sonika.jindal@...el.com>
      Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
      Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>

The commit does not revert cleanly, but this patch resolves the issue:

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index e6c035b0fc1c..8cefb9105f26 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1393,7 +1393,7 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 
        intel_hdmi_unset_edid(connector);
 
-       if (intel_hdmi_set_edid(connector, live_status)) {
+       if (intel_hdmi_set_edid(connector, true)) {
                struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
 
                hdmi_to_dig_port(intel_hdmi)->base.type = INTEL_OUTPUT_HDMI;

Let me know if you need any more info.

Thanks,
  Nick