drm/vc4: Initialize scaler DISPBKGND on modeset.

We weren't updating the interlaced bit, so we'd scan out incorrectly
if the firmware had brought up the TV encoder and we were switching to
HDMI.

Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -183,6 +183,8 @@ static int vc4_get_clock_select(struct drm_crtc *crtc)
 
 static void vc4_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
+	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
 	struct drm_crtc_state *state = crtc->state;
 	struct drm_display_mode *mode = &state->adjusted_mode;
@@ -251,6 +253,10 @@ static void vc4_crtc_mode_set_nofb(struct drm_crtc *crtc)
 		   PV_CONTROL_FIFO_CLR |
 		   PV_CONTROL_EN);
 
+	HVS_WRITE(SCALER_DISPBKGNDX(vc4_crtc->channel),
+		  SCALER_DISPBKGND_AUTOHS |
+		  (interlace ? SCALER_DISPBKGND_INTERLACE : 0));
+
 	if (debug_dump_regs) {
 		DRM_INFO("CRTC %d regs after:\n", drm_crtc_index(crtc));
 		vc4_crtc_dump_regs(vc4_crtc);

drivers/gpu/drm/vc4/vc4_regs.h

@@ -350,6 +350,17 @@
 # define SCALER_DISPCTRLX_HEIGHT_SHIFT		0
 
 #define SCALER_DISPBKGND0                       0x00000044
+# define SCALER_DISPBKGND_AUTOHS		BIT(31)
+# define SCALER_DISPBKGND_INTERLACE		BIT(30)
+# define SCALER_DISPBKGND_GAMMA			BIT(29)
+# define SCALER_DISPBKGND_TESTMODE_MASK		VC4_MASK(28, 25)
+# define SCALER_DISPBKGND_TESTMODE_SHIFT	25
+/* Enables filling the scaler line with the RGB value in the low 24
+ * bits before compositing.  Costs cycles, so should be skipped if
+ * opaque display planes will cover everything.
+ */
+# define SCALER_DISPBKGND_FILL			BIT(24)
+
 #define SCALER_DISPSTAT0                        0x00000048
 #define SCALER_DISPBASE0                        0x0000004c
 # define SCALER_DISPSTATX_MODE_MASK		VC4_MASK(31, 30)
@@ -362,6 +373,9 @@
 # define SCALER_DISPSTATX_EMPTY			BIT(28)
 #define SCALER_DISPCTRL1                        0x00000050
 #define SCALER_DISPBKGND1                       0x00000054
+#define SCALER_DISPBKGNDX(x)			(SCALER_DISPBKGND0 +        \
+						 (x) * (SCALER_DISPBKGND1 - \
+							SCALER_DISPBKGND0))
 #define SCALER_DISPSTAT1                        0x00000058
 #define SCALER_DISPSTATX(x)			(SCALER_DISPSTAT0 +        \
 						 (x) * (SCALER_DISPSTAT1 - \