sfc: Leave interrupts and event queues enabled whenever we can

When SR-IOV is enabled we may receive FLR (Function-Level Reset)
events, associated queue flush events and requests from VF drivers at
any time.  Therefore we need to keep event queues and interrupts
enabled whenever possible.

Currently we stop interrupt-driven event processing before flushing RX
and TX queues; efx_nic_flush_queues() then polls event queues for
flush events and discards any others it finds.  Change it to work with
the regular event handling functions.

Currently efx_start_channel() fills RX queues synchronously when a
device is brought up.  This could now race with NAPI, so change it to
send fill events.

This was almost entirely written by Steve Hodgson, formerly
shodgson@solarflare.com.

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

1 files changed, 109 insertions, 128 deletions

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index ce07aa516cd..ccfb43c9968 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -186,6 +186,8 @@ MODULE_PARM_DESC(debug, "Bitmapped debugging message enable value");
  *
  *************************************************************************/
 
+static void efx_start_interrupts(struct efx_nic *efx);
+static void efx_stop_interrupts(struct efx_nic *efx);
 static void efx_remove_channels(struct efx_nic *efx);
 static void efx_remove_port(struct efx_nic *efx);
 static void efx_init_napi(struct efx_nic *efx);
@@ -217,10 +219,9 @@ static void efx_stop_all(struct efx_nic *efx);
  */
 static int efx_process_channel(struct efx_channel *channel, int budget)
 {
-	struct efx_nic *efx = channel->efx;
 	int spent;
 
-	if (unlikely(efx->reset_pending || !channel->enabled))
+	if (unlikely(!channel->enabled))
 		return 0;
 
 	spent = efx_nic_process_eventq(channel, budget);
@@ -233,9 +234,10 @@ static int efx_process_channel(struct efx_channel *channel, int budget)
 			__efx_rx_packet(channel, channel->rx_pkt);
 			channel->rx_pkt = NULL;
 		}
-
-		efx_rx_strategy(channel);
-		efx_fast_push_rx_descriptors(rx_queue);
+		if (rx_queue->enabled) {
+			efx_rx_strategy(channel);
+			efx_fast_push_rx_descriptors(rx_queue);
+		}
 	}
 
 	return spent;
@@ -387,6 +389,34 @@ static void efx_init_eventq(struct efx_channel *channel)
 	efx_nic_init_eventq(channel);
 }
 
+/* Enable event queue processing and NAPI */
+static void efx_start_eventq(struct efx_channel *channel)
+{
+	netif_dbg(channel->efx, ifup, channel->efx->net_dev,
+		  "chan %d start event queue\n", channel->channel);
+
+	/* The interrupt handler for this channel may set work_pending
+	 * as soon as we enable it.  Make sure it's cleared before
+	 * then.  Similarly, make sure it sees the enabled flag set.
+	 */
+	channel->work_pending = false;
+	channel->enabled = true;
+	smp_wmb();
+
+	napi_enable(&channel->napi_str);
+	efx_nic_eventq_read_ack(channel);
+}
+
+/* Disable event queue processing and NAPI */
+static void efx_stop_eventq(struct efx_channel *channel)
+{
+	if (!channel->enabled)
+		return;
+
+	napi_disable(&channel->napi_str);
+	channel->enabled = false;
+}
+
 static void efx_fini_eventq(struct efx_channel *channel)
 {
 	netif_dbg(channel->efx, drv, channel->efx->net_dev,
@@ -556,7 +586,7 @@ fail:
  * to propagate configuration changes (mtu, checksum offload), or
  * to clear hardware error conditions
  */
-static void efx_init_channels(struct efx_nic *efx)
+static void efx_start_datapath(struct efx_nic *efx)
 {
 	struct efx_tx_queue *tx_queue;
 	struct efx_rx_queue *rx_queue;
@@ -575,68 +605,26 @@ static void efx_init_channels(struct efx_nic *efx)
 
 	/* Initialise the channels */
 	efx_for_each_channel(channel, efx) {
-		netif_dbg(channel->efx, drv, channel->efx->net_dev,
-			  "init chan %d\n", channel->channel);
-
-		efx_init_eventq(channel);
-
 		efx_for_each_channel_tx_queue(tx_queue, channel)
 			efx_init_tx_queue(tx_queue);
 
 		/* The rx buffer allocation strategy is MTU dependent */
 		efx_rx_strategy(channel);
 
-		efx_for_each_channel_rx_queue(rx_queue, channel)
+		efx_for_each_channel_rx_queue(rx_queue, channel) {
 			efx_init_rx_queue(rx_queue);
+			efx_nic_generate_fill_event(rx_queue);
+		}
 
 		WARN_ON(channel->rx_pkt != NULL);
 		efx_rx_strategy(channel);
 	}
-}
-
-/* This enables event queue processing and packet transmission.
- *
- * Note that this function is not allowed to fail, since that would
- * introduce too much complexity into the suspend/resume path.
- */
-static void efx_start_channel(struct efx_channel *channel)
-{
-	struct efx_rx_queue *rx_queue;
-
-	netif_dbg(channel->efx, ifup, channel->efx->net_dev,
-		  "starting chan %d\n", channel->channel);
-
-	/* The interrupt handler for this channel may set work_pending
-	 * as soon as we enable it.  Make sure it's cleared before
-	 * then.  Similarly, make sure it sees the enabled flag set. */
-	channel->work_pending = false;
-	channel->enabled = true;
-	smp_wmb();
-
-	/* Fill the queues before enabling NAPI */
-	efx_for_each_channel_rx_queue(rx_queue, channel)
-		efx_fast_push_rx_descriptors(rx_queue);
-
-	napi_enable(&channel->napi_str);
-}
 
-/* This disables event queue processing and packet transmission.
- * This function does not guarantee that all queue processing
- * (e.g. RX refill) is complete.
- */
-static void efx_stop_channel(struct efx_channel *channel)
-{
-	if (!channel->enabled)
-		return;
-
-	netif_dbg(channel->efx, ifdown, channel->efx->net_dev,
-		  "stop chan %d\n", channel->channel);
-
-	channel->enabled = false;
-	napi_disable(&channel->napi_str);
+	if (netif_device_present(efx->net_dev))
+		netif_tx_wake_all_queues(efx->net_dev);
 }
 
-static void efx_fini_channels(struct efx_nic *efx)
+static void efx_stop_datapath(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
 	struct efx_tx_queue *tx_queue;
@@ -663,14 +651,21 @@ static void efx_fini_channels(struct efx_nic *efx)
 	}
 
 	efx_for_each_channel(channel, efx) {
-		netif_dbg(channel->efx, drv, channel->efx->net_dev,
-			  "shut down chan %d\n", channel->channel);
+		/* RX packet processing is pipelined, so wait for the
+		 * NAPI handler to complete.  At least event queue 0
+		 * might be kept active by non-data events, so don't
+		 * use napi_synchronize() but actually disable NAPI
+		 * temporarily.
+		 */
+		if (efx_channel_has_rx_queue(channel)) {
+			efx_stop_eventq(channel);
+			efx_start_eventq(channel);
+		}
 
 		efx_for_each_channel_rx_queue(rx_queue, channel)
 			efx_fini_rx_queue(rx_queue);
 		efx_for_each_possible_channel_tx_queue(tx_queue, channel)
 			efx_fini_tx_queue(tx_queue);
-		efx_fini_eventq(channel);
 	}
 }
 
@@ -706,7 +701,7 @@ efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries)
 	int rc;
 
 	efx_stop_all(efx);
-	efx_fini_channels(efx);
+	efx_stop_interrupts(efx);
 
 	/* Clone channels */
 	memset(other_channel, 0, sizeof(other_channel));
@@ -746,7 +741,7 @@ out:
 	for (i = 0; i < efx->n_channels; i++)
 		kfree(other_channel[i]);
 
-	efx_init_channels(efx);
+	efx_start_interrupts(efx);
 	efx_start_all(efx);
 	return rc;
 
@@ -1246,6 +1241,44 @@ static int efx_probe_interrupts(struct efx_nic *efx)
 	return 0;
 }
 
+/* Enable interrupts, then probe and start the event queues */
+static void efx_start_interrupts(struct efx_nic *efx)
+{
+	struct efx_channel *channel;
+
+	if (efx->legacy_irq)
+		efx->legacy_irq_enabled = true;
+	efx_nic_enable_interrupts(efx);
+
+	efx_for_each_channel(channel, efx) {
+		efx_init_eventq(channel);
+		efx_start_eventq(channel);
+	}
+
+	efx_mcdi_mode_event(efx);
+}
+
+static void efx_stop_interrupts(struct efx_nic *efx)
+{
+	struct efx_channel *channel;
+
+	efx_mcdi_mode_poll(efx);
+
+	efx_nic_disable_interrupts(efx);
+	if (efx->legacy_irq) {
+		synchronize_irq(efx->legacy_irq);
+		efx->legacy_irq_enabled = false;
+	}
+
+	efx_for_each_channel(channel, efx) {
+		if (channel->irq)
+			synchronize_irq(channel->irq);
+
+		efx_stop_eventq(channel);
+		efx_fini_eventq(channel);
+	}
+}
+
 static void efx_remove_interrupts(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
@@ -1371,15 +1404,13 @@ static int efx_probe_all(struct efx_nic *efx)
 	return rc;
 }
 
-/* Called after previous invocation(s) of efx_stop_all, restarts the
- * port, kernel transmit queue, NAPI processing and hardware interrupts,
- * and ensures that the port is scheduled to be reconfigured.
- * This function is safe to call multiple times when the NIC is in any
- * state. */
+/* Called after previous invocation(s) of efx_stop_all, restarts the port,
+ * kernel transmit queues and NAPI processing, and ensures that the port is
+ * scheduled to be reconfigured. This function is safe to call multiple
+ * times when the NIC is in any state.
+ */
 static void efx_start_all(struct efx_nic *efx)
 {
-	struct efx_channel *channel;
-
 	EFX_ASSERT_RESET_SERIALISED(efx);
 
 	/* Check that it is appropriate to restart the interface. All
@@ -1391,28 +1422,8 @@ static void efx_start_all(struct efx_nic *efx)
 	if (!netif_running(efx->net_dev))
 		return;
 
-	/* Mark the port as enabled so port reconfigurations can start, then
-	 * restart the transmit interface early so the watchdog timer stops */
 	efx_start_port(efx);
-
-	if (netif_device_present(efx->net_dev))
-		netif_tx_wake_all_queues(efx->net_dev);
-
-	efx_for_each_channel(channel, efx)
-		efx_start_channel(channel);
-
-	if (efx->legacy_irq)
-		efx->legacy_irq_enabled = true;
-	efx_nic_enable_interrupts(efx);
-
-	/* Switch to event based MCDI completions after enabling interrupts.
-	 * If a reset has been scheduled, then we need to stay in polled mode.
-	 * Rather than serialising efx_mcdi_mode_event() [which sleeps] and
-	 * reset_pending [modified from an atomic context], we instead guarantee
-	 * that efx_mcdi_mode_poll() isn't reverted erroneously */
-	efx_mcdi_mode_event(efx);
-	if (efx->reset_pending)
-		efx_mcdi_mode_poll(efx);
+	efx_start_datapath(efx);
 
 	/* Start the hardware monitor if there is one. Otherwise (we're link
 	 * event driven), we have to poll the PHY because after an event queue
@@ -1448,8 +1459,6 @@ static void efx_flush_all(struct efx_nic *efx)
  * taking locks. */
 static void efx_stop_all(struct efx_nic *efx)
 {
-	struct efx_channel *channel;
-
 	EFX_ASSERT_RESET_SERIALISED(efx);
 
 	/* port_enabled can be read safely under the rtnl lock */
@@ -1457,28 +1466,6 @@ static void efx_stop_all(struct efx_nic *efx)
 		return;
 
 	efx->type->stop_stats(efx);
-
-	/* Switch to MCDI polling on Siena before disabling interrupts */
-	efx_mcdi_mode_poll(efx);
-
-	/* Disable interrupts and wait for ISR to complete */
-	efx_nic_disable_interrupts(efx);
-	if (efx->legacy_irq) {
-		synchronize_irq(efx->legacy_irq);
-		efx->legacy_irq_enabled = false;
-	}
-	efx_for_each_channel(channel, efx) {
-		if (channel->irq)
-			synchronize_irq(channel->irq);
-	}
-
-	/* Stop all NAPI processing and synchronous rx refills */
-	efx_for_each_channel(channel, efx)
-		efx_stop_channel(channel);
-
-	/* Stop all asynchronous port reconfigurations. Since all
-	 * event processing has already been stopped, there is no
-	 * window to loose phy events */
 	efx_stop_port(efx);
 
 	/* Flush efx_mac_work(), refill_workqueue, monitor_work */
@@ -1486,9 +1473,9 @@ static void efx_stop_all(struct efx_nic *efx)
 
 	/* Stop the kernel transmit interface late, so the watchdog
 	 * timer isn't ticking over the flush */
-	netif_tx_stop_all_queues(efx->net_dev);
-	netif_tx_lock_bh(efx->net_dev);
-	netif_tx_unlock_bh(efx->net_dev);
+	netif_tx_disable(efx->net_dev);
+
+	efx_stop_datapath(efx);
 }
 
 static void efx_remove_all(struct efx_nic *efx)
@@ -1731,8 +1718,6 @@ static int efx_net_stop(struct net_device *net_dev)
 	if (efx->state != STATE_DISABLED) {
 		/* Stop the device and flush all the channels */
 		efx_stop_all(efx);
-		efx_fini_channels(efx);
-		efx_init_channels(efx);
 	}
 
 	return 0;
@@ -1803,8 +1788,6 @@ static int efx_change_mtu(struct net_device *net_dev, int new_mtu)
 
 	netif_dbg(efx, drv, efx->net_dev, "changing MTU to %d\n", new_mtu);
 
-	efx_fini_channels(efx);
-
 	mutex_lock(&efx->mac_lock);
 	/* Reconfigure the MAC before enabling the dma queues so that
 	 * the RX buffers don't overflow */
@@ -1812,8 +1795,6 @@ static int efx_change_mtu(struct net_device *net_dev, int new_mtu)
 	efx->type->reconfigure_mac(efx);
 	mutex_unlock(&efx->mac_lock);
 
-	efx_init_channels(efx);
-
 	efx_start_all(efx);
 	return 0;
 }
@@ -2030,7 +2011,7 @@ void efx_reset_down(struct efx_nic *efx, enum reset_type method)
 	efx_stop_all(efx);
 	mutex_lock(&efx->mac_lock);
 
-	efx_fini_channels(efx);
+	efx_stop_interrupts(efx);
 	if (efx->port_initialized && method != RESET_TYPE_INVISIBLE)
 		efx->phy_op->fini(efx);
 	efx->type->fini(efx);
@@ -2067,7 +2048,7 @@ int efx_reset_up(struct efx_nic *efx, enum reset_type method, bool ok)
 
 	efx->type->reconfigure_mac(efx);
 
-	efx_init_channels(efx);
+	efx_start_interrupts(efx);
 	efx_restore_filters(efx);
 
 	mutex_unlock(&efx->mac_lock);
@@ -2273,6 +2254,7 @@ static int efx_init_struct(struct efx_nic *efx, const struct efx_nic_type *type,
 	efx->phy_op = &efx_dummy_phy_operations;
 	efx->mdio.dev = net_dev;
 	INIT_WORK(&efx->mac_work, efx_mac_work);
+	init_waitqueue_head(&efx->flush_wq);
 
 	for (i = 0; i < EFX_MAX_CHANNELS; i++) {
 		efx->channel[i] = efx_alloc_channel(efx, i, NULL);
@@ -2330,8 +2312,8 @@ static void efx_pci_remove_main(struct efx_nic *efx)
 	free_irq_cpu_rmap(efx->net_dev->rx_cpu_rmap);
 	efx->net_dev->rx_cpu_rmap = NULL;
 #endif
+	efx_stop_interrupts(efx);
 	efx_nic_fini_interrupt(efx);
-	efx_fini_channels(efx);
 	efx_fini_port(efx);
 	efx->type->fini(efx);
 	efx_fini_napi(efx);
@@ -2357,6 +2339,7 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
 	/* Allow any queued efx_resets() to complete */
 	rtnl_unlock();
 
+	efx_stop_interrupts(efx);
 	efx_unregister_netdev(efx);
 
 	efx_mtd_remove(efx);
@@ -2405,16 +2388,14 @@ static int efx_pci_probe_main(struct efx_nic *efx)
 		goto fail4;
 	}
 
-	efx_init_channels(efx);
-
 	rc = efx_nic_init_interrupt(efx);
 	if (rc)
 		goto fail5;
+	efx_start_interrupts(efx);
 
 	return 0;
 
  fail5:
-	efx_fini_channels(efx);
 	efx_fini_port(efx);
  fail4:
 	efx->type->fini(efx);
@@ -2534,7 +2515,7 @@ static int efx_pm_freeze(struct device *dev)
 	netif_device_detach(efx->net_dev);
 
 	efx_stop_all(efx);
-	efx_fini_channels(efx);
+	efx_stop_interrupts(efx);
 
 	return 0;
 }
@@ -2545,7 +2526,7 @@ static int efx_pm_thaw(struct device *dev)
 
 	efx->state = STATE_INIT;
 
-	efx_init_channels(efx);
+	efx_start_interrupts(efx);
 
 	mutex_lock(&efx->mac_lock);
 	efx->phy_op->reconfigure(efx);