usb: dwc3: gadget: pretty print link states

this makes it slightly easier to read link state
change interrupt logs.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -302,6 +302,42 @@ static const char *dwc3_gadget_ep_cmd_string(u8 cmd)
 	}
 }
 
+static const char *dwc3_gadget_link_string(enum dwc3_link_state link_state)
+{
+	switch (link_state) {
+	case DWC3_LINK_STATE_U0:
+		return "U0";
+	case DWC3_LINK_STATE_U1:
+		return "U1";
+	case DWC3_LINK_STATE_U2:
+		return "U2";
+	case DWC3_LINK_STATE_U3:
+		return "U3";
+	case DWC3_LINK_STATE_SS_DIS:
+		return "SS.Disabled";
+	case DWC3_LINK_STATE_RX_DET:
+		return "RX.Detect";
+	case DWC3_LINK_STATE_SS_INACT:
+		return "SS.Inactive";
+	case DWC3_LINK_STATE_POLL:
+		return "Polling";
+	case DWC3_LINK_STATE_RECOV:
+		return "Recovery";
+	case DWC3_LINK_STATE_HRESET:
+		return "Hot Reset";
+	case DWC3_LINK_STATE_CMPLY:
+		return "Compliance";
+	case DWC3_LINK_STATE_LPBK:
+		return "Loopback";
+	case DWC3_LINK_STATE_RESET:
+		return "Reset";
+	case DWC3_LINK_STATE_RESUME:
+		return "Resume";
+	default:
+		return "UNKNOWN link state\n";
+	}
+}
+
 int dwc3_send_gadget_generic_command(struct dwc3 *dwc, int cmd, u32 param)
 {
 	u32		timeout = 500;
@@ -2449,8 +2485,6 @@ static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
 		}
 	}
 
-	dwc->link_state = next;
-
 	switch (next) {
 	case DWC3_LINK_STATE_U1:
 		if (dwc->speed == USB_SPEED_SUPER)
@@ -2468,7 +2502,11 @@ static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
 		break;
 	}
 
-	dev_vdbg(dwc->dev, "%s link %d\n", __func__, dwc->link_state);
+	dev_vdbg(dwc->dev, "link change: %s [%d] -> %s [%d]\n",
+			dwc3_gadget_link_string(dwc->link_state),
+			dwc->link_state, dwc3_gadget_link_string(next), next);
+
+	dwc->link_state = next;
 }
 
 static void dwc3_gadget_hibernation_interrupt(struct dwc3 *dwc,