[Intel-gfx] of the LVDS panel registers, and it just inherits the values. If the

[bfreed at chromium.org]

intel_display.c: ensures the sync polarity to the panel is correct
and issues a message if the driver changes it. 

If these are not correct then although the panel looks ok, output from an HDMI
encoder (eg, Chrontel CH7036) will be incorrect. 

Signed-off-by: Mark Hayter <mdhayter at chromium.org>

Index: drivers/gpu/drm/i915/i915_reg.h
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b463a0baa924ff1dee74ca8473b458927cfa0901..e325eaea4bfb289c76a093c5cada026eab6c3983 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1056,6 +1056,10 @@
 #define   LVDS_PIPEB_SELECT		(1 << 30)
 /* LVDS dithering flag on 965/g4x platform */
 #define   LVDS_ENABLE_DITHER		(1 << 25)
+/* LVDS sync polarity flags. Set to invert (i.e. negative) */
+#define   LVDS_VSYNC_POLARITY		(1 << 21)
+#define   LVDS_HSYNC_POLARITY		(1 << 20)
+
 /* Enable border for unscaled (or aspect-scaled) display */
 #define   LVDS_BORDER_ENABLE		(1 << 15)
 /*
Index: drivers/gpu/drm/i915/intel_display.c
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 787e6da01984a2c2296295359250cd436e0cf5fe..9893e53e394cc9140167b9884c05efd62c4f139c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3334,6 +3334,29 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 					lvds &= ~LVDS_ENABLE_DITHER;
 			}
 		}
+		/* Only tested on pineview, should work on IS_9XX */
+		if (IS_PINEVIEW(dev)) {
+			/* Set sync polarity for case when vbios did not */
+			char curhs, curvs, newhs, newvs;
+			curhs = (lvds & LVDS_HSYNC_POLARITY) ? '-' : '+';
+			curvs = (lvds & LVDS_VSYNC_POLARITY) ? '-' : '+';
+			newhs = (adjusted_mode->flags & DRM_MODE_FLAG_NHSYNC) ?
+				'-' : '+';
+			newvs = (adjusted_mode->flags & DRM_MODE_FLAG_NVSYNC) ?
+				'-' : '+';
+			if ((newhs != curhs) || (newvs != curvs)) {
+				DRM_INFO("Change lvds panel from %chsync "
+					 "%cvsync to %chsync %cvsync\n",
+					 curhs, curvs, newhs, newvs);
+				/* Clear to both + polarity */
+				lvds &= ~(LVDS_HSYNC_POLARITY |
+					  LVDS_VSYNC_POLARITY);
+				if (newhs == '-')
+					lvds |= LVDS_HSYNC_POLARITY;
+				if (newvs == '-')
+					lvds |= LVDS_VSYNC_POLARITY;
+			}
+		}
 		I915_WRITE(lvds_reg, lvds);
 		I915_READ(lvds_reg);
 	}