sfc: Stop TX queues before they fill up
We now have a definite upper bound on the number of descriptors per
skb; use that to stop the queue when the next packet might not fit.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 65a8d49..3b3f084 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -630,6 +630,16 @@
efx->rx_buffer_order = get_order(efx->rx_buffer_len +
sizeof(struct efx_rx_page_state));
+ /* We must keep at least one descriptor in a TX ring empty.
+ * We could avoid this when the queue size does not exactly
+ * match the hardware ring size, but it's not that important.
+ * Therefore we stop the queue when one more skb might fill
+ * the ring completely. We wake it when half way back to
+ * empty.
+ */
+ efx->txq_stop_thresh = efx->txq_entries - efx_tx_max_skb_descs(efx);
+ efx->txq_wake_thresh = efx->txq_stop_thresh / 2;
+
/* Initialise the channels */
efx_for_each_channel(channel, efx) {
efx_for_each_channel_tx_queue(tx_queue, channel)