usb: dwc2: gadget: initialize max_speed from params

DWC2 may be paired with a full-speed PHY which is not capable of
high-speed operation.  Report this correctly to the gadget core by
setting max_speed from the core parameters.

Prior to commit 5324bad ("usb: dwc2: gadget: implement
udc_set_speed()") this didn't cause the hardware to be configured
incorrectly, although the speed may have been reported incorrectly.  But
after that commit params.speed is updated based on a value passed in by
the gadget core which may set it to a faster speed than is supported by
the hardware.  Initialising the max_speed parameter ensures the speed
passed to dwc2_gadget_set_speed() will be one supported by the hardware.

Fixes: 5324bad ("usb: dwc2: gadget: implement udc_set_speed()")
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20220106115731.1473909-1-john@metanate.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: johnkeeping

drivers/usb/dwc2/gadget.c

@@ -4974,7 +4974,18 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg)
 		hsotg->params.g_np_tx_fifo_size);
 	dev_dbg(dev, "RXFIFO size: %d\n", hsotg->params.g_rx_fifo_size);
 
-	hsotg->gadget.max_speed = USB_SPEED_HIGH;
+	switch (hsotg->params.speed) {
+	case DWC2_SPEED_PARAM_LOW:
+		hsotg->gadget.max_speed = USB_SPEED_LOW;
+		break;
+	case DWC2_SPEED_PARAM_FULL:
+		hsotg->gadget.max_speed = USB_SPEED_FULL;
+		break;
+	default:
+		hsotg->gadget.max_speed = USB_SPEED_HIGH;
+		break;
+	}
+
 	hsotg->gadget.ops = &dwc2_hsotg_gadget_ops;
 	hsotg->gadget.name = dev_name(dev);
 	hsotg->gadget.otg_caps = &hsotg->params.otg_caps;