drm/tegra: dc: Support background color

Starting with Tegra124, the interface to set the background color (the
value generated for pixels that are not sourced from any window) is via
a different register. Earlier generations called this the border color.
Reverse the feature flag and assume that IP revisions that don't have
support for background color will support border color instead.

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/tegra/dc.h b/drivers/gpu/drm/tegra/dc.h
index 032c734..571a6c78 100644
--- a/drivers/gpu/drm/tegra/dc.h
+++ b/drivers/gpu/drm/tegra/dc.h
@@ -26,7 +26,7 @@
 };
 
 struct tegra_dc_soc_info {
-	bool supports_border_color;
+	bool supports_background_color;
 	bool supports_interlacing;
 	bool supports_cursor;
 	bool supports_block_linear;
@@ -447,6 +447,12 @@
 #define DC_DISP_SD_HW_K_VALUES			0x4dd
 #define DC_DISP_SD_MAN_K_VALUES			0x4de
 
+#define DC_DISP_BLEND_BACKGROUND_COLOR		0x4e4
+#define  BACKGROUND_COLOR_ALPHA(x) (((x) & 0xff) << 24)
+#define  BACKGROUND_COLOR_BLUE(x)  (((x) & 0xff) << 16)
+#define  BACKGROUND_COLOR_GREEN(x) (((x) & 0xff) << 8)
+#define  BACKGROUND_COLOR_RED(x)   (((x) & 0xff) << 0)
+
 #define DC_DISP_INTERLACE_CONTROL		0x4e5
 #define  INTERLACE_STATUS (1 << 2)
 #define  INTERLACE_START  (1 << 1)