usb: dwc3: dwc3-omap: return -EPROBE_DEFER if probe has not yet executed

return -EPROBE_DEFER from dwc3_omap_mailbox in dwc3-omap.c, if the probe of
dwc3-omap has not yet been executed or failed.
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/dwc3-omap.c

@@ -138,11 +138,14 @@ static inline void dwc3_omap_writel(void __iomem *base, u32 offset, u32 value)
 	writel(value, base + offset);
 }
 
-void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
+int dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
 {
 	u32			val;
 	struct dwc3_omap	*omap = _omap;
 
+	if (!omap)
+		return -EPROBE_DEFER;
+
 	switch (status) {
 	case OMAP_DWC3_ID_GROUND:
 		dev_dbg(omap->dev, "ID GND\n");
@@ -185,7 +188,7 @@ void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
 		dev_dbg(omap->dev, "ID float\n");
 	}
 
-	return;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(dwc3_omap_mailbox);
 

include/linux/usb/dwc3-omap.h

@@ -19,11 +19,11 @@ enum omap_dwc3_vbus_id_status {
 };
 
 #if (defined(CONFIG_USB_DWC3) || defined(CONFIG_USB_DWC3_MODULE))
-extern void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status);
+extern int dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status);
 #else
-static inline void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
+static inline int dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
 {
-	return;
+	return -ENODEV;
 }
 #endif