[4.2.y-ckt stable] Patch "drm/i915: Don't override output type for DDI HDMI" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    drm/i915: Don't override output type for DDI HDMI

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 19586cd3c161d1b0f0c0dab2e44958cf2c07380a Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai at suse.de>
Date: Thu, 19 Nov 2015 12:09:56 +0100
Subject: drm/i915: Don't override output type for DDI HDMI

commit 2540058f7a9d9a843b4d9a28d4f8168dd034d030 upstream.

Currently a DDI port may register the DP hotplug handler even though
it's used with HDMI, and the DP HPD handler overrides the encoder
type forcibly to DP.  This caused the inconsistency on a machine
connected with a HDMI monitor; upon a hotplug event, the DDI port is
suddenly switched to be handled as a DP although the same monitor is
kept connected, and this leads to the erroneous blank output.

This patch papers over the bug by excluding the previous HDMI encoder
type from this override.  This should be fixed more fundamentally,
e.g. by moving the encoder type reset from the HPD or by having
individual encoder objects for HDMI and DP.  But since the bug has
been present for a long time (3.17), it's better to have a
quick-n-dirty fix for now, and keep working on a cleaner fix.

Bugzilla: http://bugzilla.opensuse.org/show_bug.cgi?id=955190
Fixes: 0e32b39ceed6 ('drm/i915: add DP 1.2 MST support (v0.7)')
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1447931396-19147-1-git-send-email-tiwai@suse.de
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index ca2d923..da3c653 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4947,7 +4947,8 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 	enum intel_display_power_domain power_domain;
 	enum irqreturn ret = IRQ_NONE;

-	if (intel_dig_port->base.type != INTEL_OUTPUT_EDP)
+	if (intel_dig_port->base.type != INTEL_OUTPUT_EDP &&
+	    intel_dig_port->base.type != INTEL_OUTPUT_HDMI)
 		intel_dig_port->base.type = INTEL_OUTPUT_DISPLAYPORT;

 	if (long_hpd && intel_dig_port->base.type == INTEL_OUTPUT_EDP) {
--
1.9.1