wl12xx: handle wrap-around overflow in released Tx blocks FW counter

When the FW Tx released blocks counter wraps around, we should correct
our calculation of released blocks. Otherwise we add a large negative
figure to our driver freed blocks counter

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>

drivers/net/wireless/wl12xx/main.c

@@ -834,8 +834,15 @@ static void wl12xx_fw_status(struct wl1271 *wl,
 		wl->tx_pkts_freed[i] = status->tx_released_pkts[i];
 	}
 
-	freed_blocks = le32_to_cpu(status->total_released_blks) -
-		       wl->tx_blocks_freed;
+	/* prevent wrap-around in total blocks counter */
+	if (likely(wl->tx_blocks_freed <=
+		   le32_to_cpu(status->total_released_blks)))
+		freed_blocks = le32_to_cpu(status->total_released_blks) -
+			       wl->tx_blocks_freed;
+	else
+		freed_blocks = 0x100000000LL - wl->tx_blocks_freed +
+			       le32_to_cpu(status->total_released_blks);
+
 	wl->tx_blocks_freed = le32_to_cpu(status->total_released_blks);
 
 	wl->tx_allocated_blocks -= freed_blocks;