drm: tegra: fix front_porch <-> back_porch mixup

Fixes wrong picture offset observed when using HDMI output with a
Technisat HD TV.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Acked-by: Mark Zhang <markz@nvidia.com>
Tested-by: Mark Zhang <markz@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 0744103..54683e4 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -102,12 +102,12 @@
 		((mode->hsync_end - mode->hsync_start) <<  0);
 	tegra_dc_writel(dc, value, DC_DISP_SYNC_WIDTH);
 
-	value = ((mode->vsync_start - mode->vdisplay) << 16) |
-		((mode->hsync_start - mode->hdisplay) <<  0);
-	tegra_dc_writel(dc, value, DC_DISP_BACK_PORCH);
-
 	value = ((mode->vtotal - mode->vsync_end) << 16) |
 		((mode->htotal - mode->hsync_end) <<  0);
+	tegra_dc_writel(dc, value, DC_DISP_BACK_PORCH);
+
+	value = ((mode->vsync_start - mode->vdisplay) << 16) |
+		((mode->hsync_start - mode->hdisplay) <<  0);
 	tegra_dc_writel(dc, value, DC_DISP_FRONT_PORCH);
 
 	value = (mode->vdisplay << 16) | mode->hdisplay;