drm/i915: mask transcoder select bits before setting them on LVDS

commit 7885d2052bd94395e337709cfba093a41f273ff1 upstream.

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>
Cc: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 9011f48d3cb14fd56c96390bd504974c992e9acd..390768fce597846222d4f8ae66c8be9ff905ea71 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5646,12 +5646,15 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
        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;