Comment 15 for bug 1852510

Probably I found the root cause of this problem.

After enabling the HIGHMEM and VMSPLIT_3G, the urb sent to the driver of dwc_otg maybe allocated in the highmem, if it is in the highmem, the usb core will not set the urb->transfer_buffer and call hcd->urb_enquenue().

With other hcd drivers, they could handle the situation of urb->transfer_buffer to be NULL, but for dwc_otg hcd driver, it returns an error unconditionally if the urb->transfer_buffer is NULL. I check the code, the dwc_otg driver could handle the situation that the urb buffer is in highmem (urb->tansfer_buffer is NULL).

Maybe we could fix this issue with a simple patch, I will post my found to the upstream bug https://github.com/raspberrypi/linux/issues/3332

hwang4@hwang4-Vostro-5390:~/work/mainline/raspi/linux-32$ git diff
diff --git a/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c b/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c
index 08a3e41038a3..5d04adfc58c0 100644
--- a/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c
+++ b/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c
@@ -821,10 +821,10 @@ static int dwc_otg_urb_enqueue(struct usb_hcd *hcd,
                dump_urb_info(urb, "dwc_otg_urb_enqueue");
        }
 #endif
-
+#if 0
        if (!urb->transfer_buffer && urb->transfer_buffer_length)
                return -EINVAL;
-
+#endif
        if ((usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS)
            || (usb_pipetype(urb->pipe) == PIPE_INTERRUPT)) {
                if (!dwc_otg_hcd_is_bandwidth_allocated