+ /*
+ * We can work in parallel with gfar_clean_tx_ring(), except
+ * when modifying num_txbdfree. Note that we didn't grab the lock
+ * when we were reading the num_txbdfree and checking for available
+ * space, that's because outside of this function it can only grow,
+ * and once we've got needed space, it cannot suddenly disappear.
+ *
+ * The lock also protects us from gfar_error(), which can modify
+ * regs->tstat and thus retrigger the transfers, which is why we
+ * also must grab the lock before setting ready bit for the first
+ * to be transmitted BD.
+ */
+ spin_lock_irqsave(&tx_queue->txlock, flags);
+