usb: host: xhci-rcar: Don't reload firmware after the completion

According to the datasheet, "Upon the completion of FW Download,
there is no need to write or reload FW.". Otherwise, it's possible
to cause unexpected behaviors. So, adds such a condition.

Fixes: 4ac8918f3a ("usb: host: xhci-plat: add support for the R-Car H2 and M2 xHCI controllers")
Cc: stable@vger.kernel.org # v3.17+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20210827063227.81990-1-yoshihiro.shimoda.uh@renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-rcar.c

@@ -134,6 +134,13 @@ static int xhci_rcar_download_firmware(struct usb_hcd *hcd)
 	const struct soc_device_attribute *attr;
 	const char *firmware_name;
 
+	/*
+	 * According to the datasheet, "Upon the completion of FW Download,
+	 * there is no need to write or reload FW".
+	 */
+	if (readl(regs + RCAR_USB3_DL_CTRL) & RCAR_USB3_DL_CTRL_FW_SUCCESS)
+		return 0;
+
 	attr = soc_device_match(rcar_quirks_match);
 	if (attr)
 		quirks = (uintptr_t)attr->data;