drm/i915: Fix HDMI mode select for Cougarpoint PCH

For real HDMI sink, CPT HDMI port has to set 'HDMI' mode flag
in order to make HDMI audio work correctly.

This is required patch for drm/i915 to enable HDMI audio on CPT PCH,
ALSA patch is at http://mailman.alsa-project.org/pipermail/alsa-devel/2010-May/027601.html

Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_reg.h

@@ -2744,6 +2744,9 @@
 #define  SDVO_ENCODING          (0)
 #define  TMDS_ENCODING          (2 << 10)
 #define  NULL_PACKET_VSYNC_ENABLE       (1 << 9)
+/* CPT */
+#define  HDMI_MODE_SELECT	(1 << 9)
+#define  DVI_MODE_SELECT	(0)
 #define  SDVOB_BORDER_ENABLE    (1 << 7)
 #define  AUDIO_ENABLE           (1 << 6)
 #define  VSYNC_ACTIVE_HIGH      (1 << 4)

drivers/gpu/drm/i915/intel_hdmi.c

@@ -59,8 +59,11 @@ static void intel_hdmi_mode_set(struct drm_encoder *encoder,
 		SDVO_VSYNC_ACTIVE_HIGH |
 		SDVO_HSYNC_ACTIVE_HIGH;
 
-	if (hdmi_priv->has_hdmi_sink)
+	if (hdmi_priv->has_hdmi_sink) {
 		sdvox |= SDVO_AUDIO_ENABLE;
+		if (HAS_PCH_CPT(dev))
+			sdvox |= HDMI_MODE_SELECT;
+	}
 
 	if (intel_crtc->pipe == 1) {
 		if (HAS_PCH_CPT(dev))