From 7885d2052bd94395e337709cfba093a41f273ff1 Mon Sep 17 00:00:00 2001
From: Jesse Barnes <jbarnes@virtuousgeek.org>
Date: Thu, 12 Jan 2012 14:51:17 -0800
Subject: [PATCH] drm/i915: mask transcoder select bits before setting them on
 LVDS
Patch-mainline: 3.3-rc2
Git-commit: 7885d2052bd94395e337709cfba093a41f273ff1

The transcoder port may changed from mode set to mode set, so make sure
to mask out the selection bits before setting the right ones or we'll
get black screens when going from transcoder B to A.

Tested-by: Vincent Vanackere <vincent.vanackere@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_display.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5655,12 +5655,15 @@
 	if (is_lvds) {
 		temp = I915_READ(PCH_LVDS);
 		temp |= LVDS_PORT_EN | LVDS_A0A2_CLKA_POWER_UP;
-		if (HAS_PCH_CPT(dev))
+		if (HAS_PCH_CPT(dev)) {
+			temp &= ~PORT_TRANS_SEL_MASK;
 			temp |= PORT_TRANS_SEL_CPT(pipe);
-		else if (pipe == 1)
-			temp |= LVDS_PIPEB_SELECT;
-		else
-			temp &= ~LVDS_PIPEB_SELECT;
+		} else {
+			if (pipe == 1)
+				temp |= LVDS_PIPEB_SELECT;
+			else
+				temp &= ~LVDS_PIPEB_SELECT;
+		}
 
 		/* set the corresponsding LVDS_BORDER bit */
 		temp |= dev_priv->lvds_border_bits;
