[PATCH V3] usb: ehci-mx6: Enable OTG detection on imx8mm and imx8mn

[Adam Ford <aford173@gmail.com>]

The imx8mm and imx8mn appear compatible with imx7d-usb
flags in the OTG driver.  If the dr_mode is defined as
host or peripheral, the device appears to operate correctly,
however the auto host/peripheral detection results in an error.

The solution isn't just adding checks for imx8mm and imx8mn to
the check for imx7, because the USB clock needs to be running
to read from the USBNC_PHY_STATUS_OFFSET register or it will hang.

Marek requested that I not enable the clocks in ehci_usb_of_to_plat,
so I modified that function to return an unknown state if the
device tree does not explicitly state whether it is a host
or a peripheral.

When the driver probes, it looks to see if it's in the unknown
state, and only then will it read the register to auto-detect.

Signed-off-by: Adam Ford <aford173@gmail.com>
---
V3:  Keep ehci_usb_of_to_plat but add the ability to return
     and unknown state instead of reading the register.
     If the probe determines the states is unknown, it will
     query the register after the clocks have been enabled.
     Because of the slight behavior change, I removed any
     review or tested tags.

V2:  Rename ehci_usb_of_to_plat to ehci_usb_dr_mode and call it
     from the probe after the clocks are enabled, but before
     the data is needed.

diff --git a/drivers/usb/host/ehci-mx6.c b/drivers/usb/host/ehci-mx6.c
index 1bd6147c76..cf44e53ff7 100644
--- a/drivers/usb/host/ehci-mx6.c
+++ b/drivers/usb/host/ehci-mx6.c
@@ -543,7 +543,7 @@ static int ehci_usb_phy_mode(struct udevice *dev)
 			plat->init_type = USB_INIT_DEVICE;
 		else
 			plat->init_type = USB_INIT_HOST;
-	} else if (is_mx7()) {
+	} else if (is_mx7() || is_imx8mm() || is_imx8mn()) {
 		phy_status = (void __iomem *)(addr +
 					      USBNC_PHY_STATUS_OFFSET);
 		val = readl(phy_status);
@@ -573,9 +573,8 @@ static int ehci_usb_of_to_plat(struct udevice *dev)
 	case USB_DR_MODE_PERIPHERAL:
 		plat->init_type = USB_INIT_DEVICE;
 		break;
-	case USB_DR_MODE_OTG:
-	case USB_DR_MODE_UNKNOWN:
-		return ehci_usb_phy_mode(dev);
+	default:
+		plat->init_type = USB_INIT_UNKNOWN;
 	};
 
 	return 0;
@@ -677,6 +676,20 @@ static int ehci_usb_probe(struct udevice *dev)
 	mdelay(1);
 #endif
 
+	/*
+	 * If the device tree didn't specify host or device,
+	 * the default is USB_INIT_UNKNOWN, so we need to check
+	 * the register. For imx8mm and imx8mn, the clocks need to be
+	 * running first, so we defer the check until they are.
+	 */
+	if (priv->init_type == USB_INIT_UNKNOWN) {
+		ret = ehci_usb_phy_mode(dev);
+		if (ret)
+			goto err_clk;
+		else
+			priv->init_type = plat->init_type;
+	}
+
 #if CONFIG_IS_ENABLED(DM_REGULATOR)
 	ret = device_get_supply_regulator(dev, "vbus-supply",
 					  &priv->vbus_supply);
diff --git a/include/usb.h b/include/usb.h
index b3851fdb4f..47d738a786 100644
--- a/include/usb.h
+++ b/include/usb.h
@@ -163,7 +163,8 @@ struct int_queue;
  */
 enum usb_init_type {
 	USB_INIT_HOST,
-	USB_INIT_DEVICE
+	USB_INIT_DEVICE,
+	USB_INIT_UNKNOWN,
 };
 
 /**********************************************************************
-- 
2.32.0