usb: dwc3: core: Properly default unspecified speed

If the maximum_speed is not specified, default the device speed base on
its HW capability. Don't prematurely check HW capability before
validating the maximum_speed device property. The device property takes
precedence in dwc->maximum_speed.

Fixes: 0e1e5c47 ("usb: dwc3: add support for USB 2.0-only core configuration")
Reported-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc3/core.c

@@ -929,13 +929,6 @@ static int dwc3_core_init(struct dwc3 *dwc)
 	 */
 	dwc3_writel(dwc->regs, DWC3_GUID, LINUX_VERSION_CODE);
 
-	/* Handle USB2.0-only core configuration */
-	if (DWC3_GHWPARAMS3_SSPHY_IFC(dwc->hwparams.hwparams3) ==
-			DWC3_GHWPARAMS3_SSPHY_IFC_DIS) {
-		if (dwc->maximum_speed == USB_SPEED_SUPER)
-			dwc->maximum_speed = USB_SPEED_HIGH;
-	}
-
 	ret = dwc3_phy_setup(dwc);
 	if (ret)
 		goto err0;
@@ -1381,6 +1374,8 @@ bool dwc3_has_imod(struct dwc3 *dwc)
 static void dwc3_check_params(struct dwc3 *dwc)
 {
 	struct device *dev = dwc->dev;
+	unsigned int hwparam_gen =
+		DWC3_GHWPARAMS3_SSPHY_IFC(dwc->hwparams.hwparams3);
 
 	/* Check for proper value of imod_interval */
 	if (dwc->imod_interval && !dwc3_has_imod(dwc)) {
@@ -1412,17 +1407,23 @@ static void dwc3_check_params(struct dwc3 *dwc)
 			dwc->maximum_speed);
 		fallthrough;
 	case USB_SPEED_UNKNOWN:
-		/* default to superspeed */
-		dwc->maximum_speed = USB_SPEED_SUPER;
-
-		/*
-		 * default to superspeed plus if we are capable.
-		 */
-		if ((DWC3_IP_IS(DWC31) || DWC3_IP_IS(DWC32)) &&
-		    (DWC3_GHWPARAMS3_SSPHY_IFC(dwc->hwparams.hwparams3) ==
-		     DWC3_GHWPARAMS3_SSPHY_IFC_GEN2))
+		switch (hwparam_gen) {
+		case DWC3_GHWPARAMS3_SSPHY_IFC_GEN2:
 			dwc->maximum_speed = USB_SPEED_SUPER_PLUS;
-
+			break;
+		case DWC3_GHWPARAMS3_SSPHY_IFC_GEN1:
+			if (DWC3_IP_IS(DWC32))
+				dwc->maximum_speed = USB_SPEED_SUPER_PLUS;
+			else
+				dwc->maximum_speed = USB_SPEED_SUPER;
+			break;
+		case DWC3_GHWPARAMS3_SSPHY_IFC_DIS:
+			dwc->maximum_speed = USB_SPEED_HIGH;
+			break;
+		default:
+			dwc->maximum_speed = USB_SPEED_SUPER;
+			break;
+		}
 		break;
 	}
 }