[4.2.y-ckt stable] Patch "drm/i915/dsi: fix CHV dsi encoder hardware state readout on port C" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

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

    drm/i915/dsi: fix CHV dsi encoder hardware state readout on port C

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

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt12.

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 870cd53e28e6165743b77866aa0a4390ac516b99 Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula at intel.com>
Date: Fri, 15 Apr 2016 15:47:31 +0300
Subject: drm/i915/dsi: fix CHV dsi encoder hardware state readout on port C
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit e6f577893d0a4c1f62585bc426ab32d88593d7da upstream.

Due to "some hardware limitation" the DPI enable bit in port C control
register does not get set on VLV. As a workaround we check the status in
pipe B conf register instead. The workaround was added in

commit c0beefd29fcb1ca998f0f9ba41be8539f8eeba9b
Author: Gaurav K Singh <gaurav.k.singh at intel.com>
Date:   Tue Dec 9 10:59:20 2014 +0530

    drm/i915: Software workaround for getting the HW status of DSI Port C on BYT

Empirical evidence (on Surface 3 with DSI on port C per VBT) shows that
this is the case also on CHV, so extend the workaround to CHV. We still
have the device ready register check in place, so this should not get
confused with e.g. HDMI on pipe B.

This fixes a number of state checker warnings on CHV DSI port C.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460724451-13810-1-git-send-email-jani.nikula@intel.com
[ kamal: backport to 4.2-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/intel_dsi.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 68b25dd..d03690e 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -600,12 +600,12 @@ static bool intel_dsi_get_hw_state(struct intel_encoder *encoder,
 		dpi_enabled = I915_READ(MIPI_PORT_CTRL(port)) &
 							DPI_ENABLE;

-		/* Due to some hardware limitations on BYT, MIPI Port C DPI
-		 * Enable bit does not get set. To check whether DSI Port C
-		 * was enabled in BIOS, check the Pipe B enable bit
+		/*
+		 * Due to some hardware limitations on VLV/CHV, the DPI enable
+		 * bit in port C control register does not get set. As a
+		 * workaround, check pipe B conf instead.
 		 */
-		if (IS_VALLEYVIEW(dev) && !IS_CHERRYVIEW(dev) &&
-		    (port == PORT_C))
+		if ((IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev)) && port == PORT_C)
 			dpi_enabled = I915_READ(PIPECONF(PIPE_B)) &
 							PIPECONF_ENABLE;

--
2.7.4