[PATCH v2 1/2] usb: dwc3-generic: set "mode" based on caller of dwc3_generic_probe()

[Siddharth Vadapalli]

There are only two callers of "dwc3_generic_probe()", namely:
1. dwc3_generic_peripheral_probe()
2. dwc3_generic_host_probe()
Currently, the "mode" is set based on the device-tree node of the
platform device. Also, the DWC3 core doesn't support updating the "mode"
dynamically at runtime if it is set to "OTG", i.e. "OTG" is treated as a
separate mode in itself, rather than being treated as a mode which should
eventually lead to "host"/"peripheral".

Given that the callers of "dwc3_generic_probe()" clarify the expected
"mode" of the USB Controller, use that "mode" instead of the one
specified in the device-tree. This shall allow the USB Controller to
function both as a "Host" and as a "Peripheral" when the "mode" is "otg"
in the device-tree, based on the caller of "dwc3_generic_probe()".

Ideally, the USB ID pin should be used to determine whether or not the
requested role can be enabled. However, that can be implemented in the
future as an incremental feature over the current implementation.

Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
---

v1:
https://patchwork.ozlabs.org/project/uboot/list/?series=434253&state=%2A&archive=both
Changes since v1:
- Based on the feedback received on the v1 series, the device-tree
  specified role is also taken into account in dwc3_generic_probe(), in
  addition to the caller of dwc3_generic_probe().

 drivers/usb/dwc3/dwc3-generic.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
index 2ab41cbae45..fe98b50c42c 100644
--- a/drivers/usb/dwc3/dwc3-generic.c
+++ b/drivers/usb/dwc3/dwc3-generic.c
@@ -51,7 +51,8 @@ struct dwc3_generic_host_priv {
 };
 
 static int dwc3_generic_probe(struct udevice *dev,
-			      struct dwc3_generic_priv *priv)
+			      struct dwc3_generic_priv *priv,
+			      enum usb_dr_mode mode)
 {
 	int rc;
 	struct dwc3_generic_plat *plat = dev_get_plat(dev);
@@ -62,7 +63,19 @@ static int dwc3_generic_probe(struct udevice *dev,
 
 	dwc3->dev = dev;
 	dwc3->maximum_speed = plat->maximum_speed;
-	dwc3->dr_mode = plat->dr_mode;
+
+	/*
+	 * If the controller supports OTG as indicated by plat->dr_mode,
+	 * then either Host or Peripheral mode is acceptable.
+	 * Otherwise, error out since the platform cannot support the mode
+	 * being requested by the caller of dwc3_generic_probe().
+	 */
+	if (plat->dr_mode != mode && plat->dr_mode != USB_DR_MODE_OTG) {
+		pr_err("Requested usb mode is not supported by platform\n");
+		return -EINVAL;
+	}
+	dwc3->dr_mode = mode;
+
 #if CONFIG_IS_ENABLED(OF_CONTROL)
 	dwc3_of_parse(dwc3);
 
@@ -197,7 +210,7 @@ static int dwc3_generic_peripheral_probe(struct udevice *dev)
 {
 	struct dwc3_generic_priv *priv = dev_get_priv(dev);
 
-	return dwc3_generic_probe(dev, priv);
+	return dwc3_generic_probe(dev, priv, USB_DR_MODE_PERIPHERAL);
 }
 
 static int dwc3_generic_peripheral_remove(struct udevice *dev)
@@ -241,7 +254,7 @@ static int dwc3_generic_host_probe(struct udevice *dev)
 	struct dwc3_generic_host_priv *priv = dev_get_priv(dev);
 	int rc;
 
-	rc = dwc3_generic_probe(dev, &priv->gen_priv);
+	rc = dwc3_generic_probe(dev, &priv->gen_priv, USB_DR_MODE_HOST);
 	if (rc)
 		return rc;
 
-- 
2.43.0