sfc: Remove ancient support for nesting of TX stop

Long before this driver went into mainline, it had support for
multiple TX queues per port, with lockless TX enabled.  Since Linux
did not know anything of this, filling up any hardware TX queue would
stop the core TX queue and multiple hardware TX queues could fill up
before the scheduler reacted.  Thus it was necessary to keep a count
of how many TX queues were stopped and to wake the core TX queue only
when all had free space again.

The driver also previously (ab)used the per-hardware-queue stopped
flag as a counter to deal with various things that can inhibit TX, but
it no longer does that.

Remove the per-channel tx_stop_count, tx_stop_lock and
per-hardware-queue stopped count and just use the networking core
queue state directly.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 2 insertions, 9 deletions

diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index 294379faca4a..bdce66ddf93a 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -136,6 +136,7 @@ struct efx_tx_buffer {
  * @efx: The associated Efx NIC
  * @queue: DMA queue number
  * @channel: The associated channel
+ * @core_txq: The networking core TX queue structure
  * @buffer: The software buffer ring
  * @txd: The hardware descriptor ring
  * @ptr_mask: The size of the ring minus 1.
@@ -148,8 +149,6 @@ struct efx_tx_buffer {
  *      variable indicates that the queue is empty.  This is to
  *      avoid cache-line ping-pong between the xmit path and the
  *      completion path.
- * @stopped: Stopped count.
- *      Set if this TX queue is currently stopping its port.
  * @insert_count: Current insert pointer
  *      This is the number of buffers that have been added to the
  *      software ring.
@@ -179,6 +178,7 @@ struct efx_tx_queue {
         struct efx_nic *efx ____cacheline_aligned_in_smp;
         unsigned queue;
         struct efx_channel *channel;
+        struct netdev_queue *core_txq;
         struct efx_tx_buffer *buffer;
         struct efx_special_buffer txd;
         unsigned int ptr_mask;
@@ -187,7 +187,6 @@ struct efx_tx_queue {
         /* Members used mainly on the completion path */
         unsigned int read_count ____cacheline_aligned_in_smp;
         unsigned int old_write_count;
-        int stopped;
 
         /* Members used only on the xmit path */
         unsigned int insert_count ____cacheline_aligned_in_smp;
@@ -340,8 +339,6 @@ enum efx_rx_alloc_method {
  * @n_rx_overlength: Count of RX_OVERLENGTH errors
  * @n_skbuff_leaks: Count of skbuffs leaked due to RX overrun
  * @rx_queue: RX queue for this channel
- * @tx_stop_count: Core TX queue stop count
- * @tx_stop_lock: Core TX queue stop lock
  * @tx_queue: TX queues for this channel
  */
 struct efx_channel {
@@ -380,10 +377,6 @@ struct efx_channel {
         bool rx_pkt_csummed;
 
         struct efx_rx_queue rx_queue;
-
-        atomic_t tx_stop_count;
-        spinlock_t tx_stop_lock;
-
         struct efx_tx_queue tx_queue[2];
 };