usb: dwc2: Avoid delay when initializing USB peripheral by dwc2

When `usb start` is called on the terminal, the dwc2 driver will try
to start every USB device as host first, even if it is explicitly
configured as peripheral in the device tree (dr_mode = "peripheral").

So to avoid an unwanted 15 seconds delay when initializing the usb
(one second per channel = 1s x 15), this patch adds a check to the
initialization, and will skip host initialization of the device is
explicitly set as peripheral. The checking is already done similarly
in the `drivers/usb/gadget/dwc2_udc_otg.c` driver.

Signed-off-by: João Loureiro <joaofl@gmail.com>

drivers/usb/host/dwc2.c

@@ -21,6 +21,7 @@
 #include <asm/io.h>
 #include <dm/device_compat.h>
 #include <linux/delay.h>
+#include <linux/usb/otg.h>
 #include <power/regulator.h>
 #include <reset.h>
 
@@ -1204,7 +1205,13 @@ static int dwc2_init_common(struct udevice *dev, struct dwc2_priv *priv)
 #endif
 
 	dwc_otg_core_init(dev);
-	dwc_otg_core_host_init(dev, regs);
+
+	if (usb_get_dr_mode(dev_ofnode(dev)) == USB_DR_MODE_PERIPHERAL) {
+		dev_dbg(dev, "USB device %s dr_mode set to %d. Skipping host_init.\n",
+			dev->name, usb_get_dr_mode(dev_ofnode(dev)));
+	} else {
+		dwc_otg_core_host_init(dev, regs);
+	}
 
 	clrsetbits_le32(&regs->hprt0, DWC2_HPRT0_PRTENA |
 			DWC2_HPRT0_PRTCONNDET | DWC2_HPRT0_PRTENCHNG |