From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nick Bowler <nbowler@draconx.ca>
Subject: PROBLEM: Intel HDMI output busticated on 4.4 (regression)
Date: Tue, 19 Jan 2016 17:26:22 -0500
Message-ID: <20160119222622.GA16397@draconx.ca>
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To: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Cc: Sonika Jindal <sonika.jindal@intel.com>, Daniel Vetter <daniel.vetter@ffwll.ch>
List-Id: dri-devel@lists.freedesktop.org

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@intel.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@intel.com>
      Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
      Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
      Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.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