drm/vc4: Bring HDMI up from power off if necessary.

If the firmware hadn't brought up HDMI for us, we need to do its
power-on reset sequence (reset HD and and clear its STANDBY bits,
reset HDMI, and leave the PHY disabled).
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -495,6 +495,16 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 		goto err_put_i2c;
 	}
 
+	/* This is the rate that is set by the firmware.  The number
+	 * needs to be a bit higher than the pixel clock rate
+	 * (generally 148.5Mhz).
+	 */
+	ret = clk_set_rate(hdmi->hsm_clock, 163682864);
+	if (ret) {
+		DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
+		goto err_unprepare_pix;
+	}
+
 	ret = clk_prepare_enable(hdmi->hsm_clock);
 	if (ret) {
 		DRM_ERROR("Failed to turn on HDMI state machine clock: %d\n",
@@ -516,7 +526,24 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 	vc4->hdmi = hdmi;
 
 	/* HDMI core must be enabled. */
-	WARN_ON_ONCE((HD_READ(VC4_HD_M_CTL) & VC4_HD_M_ENABLE) == 0);
+	if (!(HD_READ(VC4_HD_M_CTL) & VC4_HD_M_ENABLE)) {
+		HD_WRITE(VC4_HD_M_CTL, VC4_HD_M_SW_RST);
+		udelay(1);
+		HD_WRITE(VC4_HD_M_CTL, 0);
+
+		HD_WRITE(VC4_HD_M_CTL, VC4_HD_M_ENABLE);
+
+		HDMI_WRITE(VC4_HDMI_SW_RESET_CONTROL,
+			   VC4_HDMI_SW_RESET_HDMI |
+			   VC4_HDMI_SW_RESET_FORMAT_DETECT);
+
+		HDMI_WRITE(VC4_HDMI_SW_RESET_CONTROL, 0);
+
+		/* PHY should be in reset, like
+		 * vc4_hdmi_encoder_disable() does.
+		 */
+		HDMI_WRITE(VC4_HDMI_TX_PHY_RESET_CTL, 0xf << 16);
+	}
 
 	drm_encoder_init(drm, hdmi->encoder, &vc4_hdmi_encoder_funcs,
 			 DRM_MODE_ENCODER_TMDS, NULL);

drivers/gpu/drm/vc4/vc4_regs.h

@@ -456,6 +456,8 @@
 #define VC4_HDMI_TX_PHY_RESET_CTL		0x2c0
 
 #define VC4_HD_M_CTL				0x00c
+# define VC4_HD_M_REGISTER_FILE_STANDBY		(3 << 6)
+# define VC4_HD_M_RAM_STANDBY			(3 << 4)
 # define VC4_HD_M_SW_RST			BIT(2)
 # define VC4_HD_M_ENABLE			BIT(0)