sfc: Fix bugs in RX queue flushing

Avoid overrunning the hardware limit of 4 concurrent RX queue flushes.
Expand the queue flush state to support this.  Make similar changes to
TX flushing to keep the code symmetric.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 73 insertions, 41 deletions

diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index 2f1f1fca0802..e1b9ce30429a 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -109,6 +109,9 @@ MODULE_PARM_DESC(rx_xon_thresh_bytes, "RX fifo XON threshold");
 /* Size and alignment of special buffers (4KB) */
 #define FALCON_BUF_SIZE 4096
 
+/* Depth of RX flush request fifo */
+#define FALCON_RX_FLUSH_COUNT 4
+
 #define FALCON_IS_DUAL_FUNC(efx)                \
         (falcon_rev(efx) < FALCON_REV_B0)
 
@@ -426,7 +429,7 @@ void falcon_init_tx(struct efx_tx_queue *tx_queue)
         efx_oword_t tx_desc_ptr;
         struct efx_nic *efx = tx_queue->efx;
 
-        tx_queue->flushed = false;
+        tx_queue->flushed = FLUSH_NONE;
 
         /* Pin TX descriptor ring */
         falcon_init_special_buffer(efx, &tx_queue->txd);
@@ -476,6 +479,8 @@ static void falcon_flush_tx_queue(struct efx_tx_queue *tx_queue)
         struct efx_nic *efx = tx_queue->efx;
         efx_oword_t tx_flush_descq;
 
+        tx_queue->flushed = FLUSH_PENDING;
+
         /* Post a flush command */
         EFX_POPULATE_OWORD_2(tx_flush_descq,
                              FRF_AZ_TX_FLUSH_DESCQ_CMD, 1,
@@ -489,7 +494,7 @@ void falcon_fini_tx(struct efx_tx_queue *tx_queue)
         efx_oword_t tx_desc_ptr;
 
         /* The queue should have been flushed */
-        WARN_ON(!tx_queue->flushed);
+        WARN_ON(tx_queue->flushed != FLUSH_DONE);
 
         /* Remove TX descriptor ring from card */
         EFX_ZERO_OWORD(tx_desc_ptr);
@@ -578,7 +583,7 @@ void falcon_init_rx(struct efx_rx_queue *rx_queue)
                 rx_queue->queue, rx_queue->rxd.index,
                 rx_queue->rxd.index + rx_queue->rxd.entries - 1);
 
-        rx_queue->flushed = false;
+        rx_queue->flushed = FLUSH_NONE;
 
         /* Pin RX descriptor ring */
         falcon_init_special_buffer(efx, &rx_queue->rxd);
@@ -607,6 +612,8 @@ static void falcon_flush_rx_queue(struct efx_rx_queue *rx_queue)
         struct efx_nic *efx = rx_queue->efx;
         efx_oword_t rx_flush_descq;
 
+        rx_queue->flushed = FLUSH_PENDING;
+
         /* Post a flush command */
         EFX_POPULATE_OWORD_2(rx_flush_descq,
                              FRF_AZ_RX_FLUSH_DESCQ_CMD, 1,
@@ -620,7 +627,7 @@ void falcon_fini_rx(struct efx_rx_queue *rx_queue)
         struct efx_nic *efx = rx_queue->efx;
 
         /* The queue should already have been flushed */
-        WARN_ON(!rx_queue->flushed);
+        WARN_ON(rx_queue->flushed != FLUSH_DONE);
 
         /* Remove RX descriptor ring from card */
         EFX_ZERO_OWORD(rx_desc_ptr);
@@ -1181,7 +1188,7 @@ static void falcon_poll_flush_events(struct efx_nic *efx)
                                                    FSF_AZ_DRIVER_EV_SUBDATA);
                         if (ev_queue < EFX_TX_QUEUE_COUNT) {
                                 tx_queue = efx->tx_queue + ev_queue;
-                                tx_queue->flushed = true;
+                                tx_queue->flushed = FLUSH_DONE;
                         }
                 } else if (ev_code == FSE_AZ_EV_CODE_DRIVER_EV &&
                            ev_sub_code == FSE_AZ_RX_DESCQ_FLS_DONE_EV) {
@@ -1191,17 +1198,29 @@ static void falcon_poll_flush_events(struct efx_nic *efx)
                                 *event, FSF_AZ_DRIVER_EV_RX_FLUSH_FAIL);
                         if (ev_queue < efx->n_rx_queues) {
                                 rx_queue = efx->rx_queue + ev_queue;
-
-                                /* retry the rx flush */
-                                if (ev_failed)
-                                        falcon_flush_rx_queue(rx_queue);
-                                else
-                                        rx_queue->flushed = true;
+                                rx_queue->flushed =
+                                        ev_failed ? FLUSH_FAILED : FLUSH_DONE;
                         }
                 }
 
+                /* We're about to destroy the queue anyway, so
+                 * it's ok to throw away every non-flush event */
+                EFX_SET_QWORD(*event);
+
                 read_ptr = (read_ptr + 1) & EFX_EVQ_MASK;
         } while (read_ptr != end_ptr);
+
+        channel->eventq_read_ptr = read_ptr;
+}
+
+static void falcon_prepare_flush(struct efx_nic *efx)
+{
+        falcon_deconfigure_mac_wrapper(efx);
+
+        /* Wait for the tx and rx fifo's to get to the next packet boundary
+         * (~1ms without back-pressure), then to drain the remainder of the
+         * fifo's at data path speeds (negligible), with a healthy margin. */
+        msleep(10);
 }
 
 /* Handle tx and rx flushes at the same time, since they run in
@@ -1211,50 +1230,56 @@ int falcon_flush_queues(struct efx_nic *efx)
 {
         struct efx_rx_queue *rx_queue;
         struct efx_tx_queue *tx_queue;
-        int i;
-        bool outstanding;
+        int i, tx_pending, rx_pending;
 
-        /* Issue flush requests */
-        efx_for_each_tx_queue(tx_queue, efx) {
-                tx_queue->flushed = false;
+        falcon_prepare_flush(efx);
+
+        /* Flush all tx queues in parallel */
+        efx_for_each_tx_queue(tx_queue, efx)
                 falcon_flush_tx_queue(tx_queue);
-        }
-        efx_for_each_rx_queue(rx_queue, efx) {
-                rx_queue->flushed = false;
-                falcon_flush_rx_queue(rx_queue);
-        }
 
-        /* Poll the evq looking for flush completions. Since we're not pushing
-         * any more rx or tx descriptors at this point, we're in no danger of
-         * overflowing the evq whilst we wait */
+        /* The hardware supports four concurrent rx flushes, each of which may
+         * need to be retried if there is an outstanding descriptor fetch */
         for (i = 0; i < FALCON_FLUSH_POLL_COUNT; ++i) {
-                msleep(FALCON_FLUSH_INTERVAL);
-                falcon_poll_flush_events(efx);
+                rx_pending = tx_pending = 0;
+                efx_for_each_rx_queue(rx_queue, efx) {
+                        if (rx_queue->flushed == FLUSH_PENDING)
+                                ++rx_pending;
+                }
+                efx_for_each_rx_queue(rx_queue, efx) {
+                        if (rx_pending == FALCON_RX_FLUSH_COUNT)
+                                break;
+                        if (rx_queue->flushed == FLUSH_FAILED ||
+                            rx_queue->flushed == FLUSH_NONE) {
+                                falcon_flush_rx_queue(rx_queue);
+                                ++rx_pending;
+                        }
+                }
+                efx_for_each_tx_queue(tx_queue, efx) {
+                        if (tx_queue->flushed != FLUSH_DONE)
+                                ++tx_pending;
+                }
 
-                /* Check if every queue has been succesfully flushed */
-                outstanding = false;
-                efx_for_each_tx_queue(tx_queue, efx)
-                        outstanding |= !tx_queue->flushed;
-                efx_for_each_rx_queue(rx_queue, efx)
-                        outstanding |= !rx_queue->flushed;
-                if (!outstanding)
+                if (rx_pending == 0 && tx_pending == 0)
                         return 0;
+
+                msleep(FALCON_FLUSH_INTERVAL);
+                falcon_poll_flush_events(efx);
         }
 
         /* Mark the queues as all flushed. We're going to return failure
-         * leading to a reset, or fake up success anyway. "flushed" now
-         * indicates that we tried to flush. */
+         * leading to a reset, or fake up success anyway */
         efx_for_each_tx_queue(tx_queue, efx) {
-                if (!tx_queue->flushed)
+                if (tx_queue->flushed != FLUSH_DONE)
                         EFX_ERR(efx, "tx queue %d flush command timed out\n",
                                 tx_queue->queue);
-                tx_queue->flushed = true;
+                tx_queue->flushed = FLUSH_DONE;
         }
         efx_for_each_rx_queue(rx_queue, efx) {
-                if (!rx_queue->flushed)
+                if (rx_queue->flushed != FLUSH_DONE)
                         EFX_ERR(efx, "rx queue %d flush command timed out\n",
                                 rx_queue->queue);
-                rx_queue->flushed = true;
+                rx_queue->flushed = FLUSH_DONE;
         }
 
         if (EFX_WORKAROUND_7803(efx))
diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index ac808d5f24a0..d0755ab056fe 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -113,6 +113,13 @@ struct efx_special_buffer {
         int entries;
 };
 
+enum efx_flush_state {
+        FLUSH_NONE,
+        FLUSH_PENDING,
+        FLUSH_FAILED,
+        FLUSH_DONE,
+};
+
 /**
  * struct efx_tx_buffer - An Efx TX buffer
  * @skb: The associated socket buffer.
@@ -189,7 +196,7 @@ struct efx_tx_queue {
         struct efx_nic *nic;
         struct efx_tx_buffer *buffer;
         struct efx_special_buffer txd;
-        bool flushed;
+        enum efx_flush_state flushed;
 
         /* Members used mainly on the completion path */
         unsigned int read_count ____cacheline_aligned_in_smp;
@@ -284,7 +291,7 @@ struct efx_rx_queue {
         struct page *buf_page;
         dma_addr_t buf_dma_addr;
         char *buf_data;
-        bool flushed;
+        enum efx_flush_state flushed;
 };
 
 /**