drm: apple: Adjust startup sequence and timing for dptx

DPTX setup from an initialized connection and display with sleeping and
reset dcp is unfortunately quite fragile. The display connection has to
be stopped and reestablished. Goodbye flicker free boot.
If the IOMFB endpoint is started too early dcp might provide incomplete
timing modes which prevent modesets.
On display standby a HPD is triggered should result in a fully
initialized dcp. If not a display cable unplug and plug should help.
MacOS doesn't handle this at all and just gives up.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/apple/apple_drv.c

@@ -8,6 +8,7 @@
  */
 
 #include <linux/component.h>
+#include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
@@ -444,7 +445,10 @@ static int apple_drm_init_dcp(struct device *dev)
 	if (num_dcp < 1)
 		return -ENODEV;
 
-	timeout = get_jiffies_64() + msecs_to_jiffies(500);
+	/*
+	 * Starting DPTX might take some time.
+	 */
+	timeout = get_jiffies_64() + msecs_to_jiffies(3000);
 
 	for (i = 0; i < num_dcp; ++i) {
 		u64 jiffies = get_jiffies_64();
@@ -459,6 +463,8 @@ static int apple_drm_init_dcp(struct device *dev)
 		if (ret)
 			dev_warn(dev, "DCP[%d] not ready: %d\n", i, ret);
 	}
+	/* HACK: Wait for dcp* to settle before a modeset */
+	msleep(100);
 
 	return 0;
 }

drivers/gpu/drm/apple/dcp.c

@@ -345,23 +345,40 @@ int dcp_start(struct platform_device *pdev)
 	if (ret)
 		dev_warn(dcp->dev, "Failed to start system endpoint: %d", ret);
 
-	if (dcp->phy) {
-		if (dcp->fw_compat >= DCP_FIRMWARE_V_13_5) {
-			ret = ibootep_init(dcp);
-			if (ret)
-				dev_warn(dcp->dev,
-					 "Failed to start IBOOT endpoint: %d",
-					 ret);
-
-			ret = dptxep_init(dcp);
-			if (ret)
-				dev_warn(dcp->dev,
-					 "Failed to start DPTX endpoint: %d",
-					 ret);
-		} else
-			dev_warn(dcp->dev,
-				 "OS firmware incompatible with dptxport EP\n");
-	}
+	if (dcp->phy && dcp->fw_compat >= DCP_FIRMWARE_V_13_5) {
+		ret = ibootep_init(dcp);
+		if (ret)
+			dev_warn(dcp->dev, "Failed to start IBOOT endpoint: %d",
+				 ret);
+
+		ret = dptxep_init(dcp);
+		if (ret)
+			dev_warn(dcp->dev, "Failed to start DPTX endpoint: %d",
+				 ret);
+		else if (dcp->dptxport[0].enabled) {
+			bool connected;
+			/* force disconnect on start - necessary if the display
+			 * is already up from m1n1
+			 */
+			dptxport_set_hpd(dcp->dptxport[0].service, false);
+			dptxport_release_display(dcp->dptxport[0].service);
+			usleep_range(10 * USEC_PER_MSEC, 25 * USEC_PER_MSEC);
+
+			connected = gpiod_get_value_cansleep(dcp->hdmi_hpd);
+			dev_info(dcp->dev, "%s: DP2HDMI HPD connected:%d\n", __func__, connected);
+
+			// necessary on j473/j474 but not on j314c
+			if (connected)
+				dcp_dptx_connect(dcp, 0);
+			/*
+			 * Long sleep necessary to ensure dcp delivers timing
+			 * modes with matched color modes.
+			 * 400ms was sufficient on j473
+			 */
+			msleep(500);
+		}
+	} else if (dcp->phy)
+		dev_warn(dcp->dev, "OS firmware incompatible with dptxport EP\n");
 
 	ret = iomfb_start_rtkit(dcp);
 	if (ret)
@@ -373,17 +390,8 @@ EXPORT_SYMBOL(dcp_start);
 
 static int dcp_enable_dp2hdmi_hpd(struct apple_dcp *dcp)
 {
-	if (dcp->hdmi_hpd) {
-		bool connected = gpiod_get_value_cansleep(dcp->hdmi_hpd);
-		dev_info(dcp->dev, "%s: DP2HDMI HPD connected:%d\n", __func__, connected);
-
-		// necessary on j473/j474 but not on j314c
-		if (connected)
-			dcp_dptx_connect(dcp, 0);
-
-		if (dcp->hdmi_hpd_irq)
-			enable_irq(dcp->hdmi_hpd_irq);
-	}
+	if (dcp->hdmi_hpd_irq)
+		enable_irq(dcp->hdmi_hpd_irq);
 
 	return 0;
 }