rt2x00: check number of EPROTO errors

Some USB host devices/drivers on some conditions can always return
EPROTO error on submitted URBs. That can cause infinity loop in the
rt2x00 driver.

Since we can have single EPROTO errors we can not mark as device as
removed to avoid infinity loop. However we can count consecutive
EPROTO errors and mark device as removed if get lot of it.
I choose number 10 as threshold.
Reported-and-tested-by: Randy Oostdyk <linux-kernel@oostdyk.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2x00.h

@@ -1016,6 +1016,7 @@ struct rt2x00_dev {
 	unsigned int extra_tx_headroom;
 
 	struct usb_anchor *anchor;
+	unsigned int num_proto_errs;
 
 	/* Clock for System On Chip devices. */
 	struct clk *clk;

drivers/net/wireless/ralink/rt2x00/rt2x00usb.c

@@ -31,6 +31,22 @@
 #include "rt2x00.h"
 #include "rt2x00usb.h"
 
+static bool rt2x00usb_check_usb_error(struct rt2x00_dev *rt2x00dev, int status)
+{
+	if (status == -ENODEV || status == -ENOENT)
+		return true;
+
+	if (status == -EPROTO || status == -ETIMEDOUT)
+		rt2x00dev->num_proto_errs++;
+	else
+		rt2x00dev->num_proto_errs = 0;
+
+	if (rt2x00dev->num_proto_errs > 3)
+		return true;
+
+	return false;
+}
+
 /*
  * Interfacing with the HW.
  */
@@ -57,7 +73,7 @@ int rt2x00usb_vendor_request(struct rt2x00_dev *rt2x00dev,
 		if (status >= 0)
 			return 0;
 
-		if (status == -ENODEV || status == -ENOENT) {
+		if (rt2x00usb_check_usb_error(rt2x00dev, status)) {
 			/* Device has disappeared. */
 			clear_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
 			break;
@@ -321,7 +337,7 @@ static bool rt2x00usb_kick_tx_entry(struct queue_entry *entry, void *data)
 
 	status = usb_submit_urb(entry_priv->urb, GFP_ATOMIC);
 	if (status) {
-		if (status == -ENODEV || status == -ENOENT)
+		if (rt2x00usb_check_usb_error(rt2x00dev, status))
 			clear_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
 		set_bit(ENTRY_DATA_IO_FAILED, &entry->flags);
 		rt2x00lib_dmadone(entry);
@@ -410,7 +426,7 @@ static bool rt2x00usb_kick_rx_entry(struct queue_entry *entry, void *data)
 
 	status = usb_submit_urb(entry_priv->urb, GFP_ATOMIC);
 	if (status) {
-		if (status == -ENODEV || status == -ENOENT)
+		if (rt2x00usb_check_usb_error(rt2x00dev, status))
 			clear_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
 		set_bit(ENTRY_DATA_IO_FAILED, &entry->flags);
 		rt2x00lib_dmadone(entry);