[PATCH] usb: dwc3: respect role-switch-default-mode

[Caleb Connolly]

* Factor out the common pattern of checking the dr_mode property on
  the usb node and it's parent
* Respect the usb-role-switch property, rather than requiring dr_mode be
  set
* Override OTG mode with the value in role-switch-default-mode

The devicetree bindings don't dictate that dr_mode is a required
property, but the dwc3 driver would refuse to probe if it was unset
(this breaks the Qualcomm RB2 board which doesn't set it).

Here, we update the driver to respect the other properties that can be
used to describe the controller, and more gracefully handle some of the
edge cases.

Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
---
Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
Cc: Neil Armstrong <neil.armstrong at linaro.org>
---
 drivers/usb/dwc3/dwc3-generic.c | 56 +++++++++++++++++++++++++--------
 1 file changed, 43 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
index cbb5d61dfb0b..1cf8b90e8bbf 100644
--- a/drivers/usb/dwc3/dwc3-generic.c
+++ b/drivers/usb/dwc3/dwc3-generic.c
@@ -49,8 +49,46 @@ struct dwc3_generic_host_priv {
 	struct dwc3_generic_priv gen_priv;
 	struct udevice *vbus_supply;
 };
 
+/**
+ * dwc3_get_preferred_dr_mode() - Get the preferred DR mode for the USB node
+ *
+ * Since we don't support dynamic role switching yet in dwc3, this is a slightly
+ * opinionated wrapper around usb_get_dr_mode() which will respect the
+ * role-switch-default-mode property if it is present and the dr_mode is OTG.
+ *
+ * @child: Node to get the DR mode for
+ */
+static enum usb_dr_mode dwc3_get_preferred_dr_mode(ofnode node)
+{
+	enum usb_dr_mode mode;
+	bool is_role_switch = ofnode_has_property(node, "usb-role-switch");
+
+	mode = usb_get_dr_mode(node);
+	/* Attempt to search the parent node too */
+	if (mode == USB_DR_MODE_UNKNOWN) {
+		node = ofnode_get_parent(node);
+		mode = usb_get_dr_mode(node);
+		is_role_switch |= ofnode_has_property(node, "usb-role-switch");
+	}
+
+	/* If the usb-role-switch property is present, but dr_mode isn't, then the
+	 * default is OTG.
+	 */
+	if (is_role_switch && mode == USB_DR_MODE_UNKNOWN)
+		mode = USB_DR_MODE_OTG;
+
+	/* Respect the role-switch-default-mode property */
+	if (mode == USB_DR_MODE_OTG && is_role_switch) {
+		mode = usb_get_role_switch_default_mode(node);
+		if (mode == USB_DR_MODE_UNKNOWN)
+			mode = USB_DR_MODE_OTG;
+	}
+
+	return mode;
+}
+
 static int dwc3_generic_probe(struct udevice *dev,
 			      struct dwc3_generic_priv *priv)
 {
 	int rc;
@@ -178,17 +216,12 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
 		pr_info("No USB maximum speed specified. Using super speed\n");
 		plat->maximum_speed = USB_SPEED_SUPER;
 	}
 
-	plat->dr_mode = usb_get_dr_mode(node);
+	plat->dr_mode = dwc3_get_preferred_dr_mode(node);
 	if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
-		/* might be a leaf so check the parent for mode */
-		node = dev_ofnode(dev->parent);
-		plat->dr_mode = usb_get_dr_mode(node);
-		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
-			pr_err("Invalid usb mode setup\n");
-			return -ENODEV;
-		}
+		pr_err("Invalid usb mode setup\n");
+		return -ENODEV;
 	}
 
 	return 0;
 }
@@ -541,12 +574,9 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
 	int ret;
 
 	debug("%s: subnode name: %s\n", __func__, name);
 
-	/* if the parent node doesn't have a mode check the leaf */
-	dr_mode = usb_get_dr_mode(dev_ofnode(parent));
-	if (!dr_mode)
-		dr_mode = usb_get_dr_mode(node);
+	dr_mode = dwc3_get_preferred_dr_mode(node);
 
 	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
 	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
 		debug("%s: dr_mode: OTG or Peripheral\n", __func__);
@@ -698,9 +728,9 @@ int dwc3_glue_probe(struct udevice *dev)
 
 	while (child) {
 		enum usb_dr_mode dr_mode;
 
-		dr_mode = usb_get_dr_mode(dev_ofnode(child));
+		dr_mode = dwc3_get_preferred_dr_mode(dev_ofnode(child));
 		device_find_next_child(&child);
 		if (ops && ops->glue_configure)
 			ops->glue_configure(dev, index, dr_mode);
 		index++;
-- 
2.45.0