drm/i915: set interlaced bits for TRANSCONF

I'm not sure why they are needed (I didn't notice any difference in my
tests), but these bits are in our documentation and they are also set by
the Windows driver.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -3362,7 +3362,9 @@
 #define  TRANS_FSYNC_DELAY_HB4  (3<<27)
 #define  TRANS_DP_AUDIO_ONLY    (1<<26)
 #define  TRANS_DP_VIDEO_AUDIO   (0<<26)
+#define  TRANS_INTERLACE_MASK   (7<<21)
 #define  TRANS_PROGRESSIVE      (0<<21)
+#define  TRANS_INTERLACED       (3<<21)
 #define  TRANS_8BPC             (0<<5)
 #define  TRANS_10BPC            (1<<5)
 #define  TRANS_6BPC             (2<<5)

drivers/gpu/drm/i915/intel_display.c

@@ -1266,7 +1266,7 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
 				    enum pipe pipe)
 {
 	int reg;
-	u32 val;
+	u32 val, pipeconf_val;
 
 	/* PCH only available on ILK+ */
 	BUG_ON(dev_priv->info->gen < 5);
@@ -1280,6 +1280,7 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
 
 	reg = TRANSCONF(pipe);
 	val = I915_READ(reg);
+	pipeconf_val = I915_READ(PIPECONF(pipe));
 
 	if (HAS_PCH_IBX(dev_priv->dev)) {
 		/*
@@ -1287,8 +1288,15 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
 		 * that in pipeconf reg.
 		 */
 		val &= ~PIPE_BPC_MASK;
-		val |= I915_READ(PIPECONF(pipe)) & PIPE_BPC_MASK;
+		val |= pipeconf_val & PIPE_BPC_MASK;
 	}
+
+	val &= ~TRANS_INTERLACE_MASK;
+	if ((pipeconf_val & PIPECONF_INTERLACE_MASK) == PIPECONF_INTERLACED_ILK)
+		val |= TRANS_INTERLACED;
+	else
+		val |= TRANS_PROGRESSIVE;
+
 	I915_WRITE(reg, val | TRANS_ENABLE);
 	if (wait_for(I915_READ(reg) & TRANS_STATE_ENABLE, 100))
 		DRM_ERROR("failed to enable transcoder %d\n", pipe);