3 files changed, 53 insertions, 34 deletions

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 097ed8b4a79a..e0157c03d313 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -1585,6 +1585,24 @@ void efx_init_irq_moderation(struct efx_nic *efx, unsigned int tx_usecs,
         }
 }
 
+void efx_get_irq_moderation(struct efx_nic *efx, unsigned int *tx_usecs,
+                            unsigned int *rx_usecs, bool *rx_adaptive)
+{
+        *rx_adaptive = efx->irq_rx_adaptive;
+        *rx_usecs = efx->irq_rx_moderation * EFX_IRQ_MOD_RESOLUTION;
+
+        /* If channels are shared between RX and TX, so is IRQ
+         * moderation.  Otherwise, IRQ moderation is the same for all
+         * TX channels and is not adaptive.
+         */
+        if (efx->tx_channel_offset == 0)
+                *tx_usecs = *rx_usecs;
+        else
+                *tx_usecs =
+                        efx->channel[efx->tx_channel_offset]->irq_moderation *
+                        EFX_IRQ_MOD_RESOLUTION;
+}
+
 /**************************************************************************
  *
  * Hardware monitor
diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
index 8f5acae431b9..8ca68631fce5 100644
--- a/drivers/net/ethernet/sfc/efx.h
+++ b/drivers/net/ethernet/sfc/efx.h
@@ -113,6 +113,8 @@ extern int efx_reset_up(struct efx_nic *efx, enum reset_type method, bool ok);
 extern void efx_schedule_reset(struct efx_nic *efx, enum reset_type type);
 extern void efx_init_irq_moderation(struct efx_nic *efx, unsigned int tx_usecs,
                                     unsigned int rx_usecs, bool rx_adaptive);
+extern void efx_get_irq_moderation(struct efx_nic *efx, unsigned int *tx_usecs,
+                                   unsigned int *rx_usecs, bool *rx_adaptive);
 
 /* Dummy PHY ops for PHY drivers */
 extern int efx_port_dummy_op_int(struct efx_nic *efx);
diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
index dedaa2c97e3c..1cb6ed0a255c 100644
--- a/drivers/net/ethernet/sfc/ethtool.c
+++ b/drivers/net/ethernet/sfc/ethtool.c
@@ -586,40 +586,37 @@ static int efx_ethtool_nway_reset(struct net_device *net_dev)
         return mdio45_nway_restart(&efx->mdio);
 }
 
+/*
+ * Each channel has a single IRQ and moderation timer, started by any
+ * completion (or other event).  Unless the module parameter
+ * separate_tx_channels is set, IRQs and moderation are therefore
+ * shared between RX and TX completions.  In this case, when RX IRQ
+ * moderation is explicitly changed then TX IRQ moderation is
+ * automatically changed too, but otherwise we fail if the two values
+ * are requested to be different.
+ *
+ * We implement adaptive IRQ moderation, but use a different algorithm
+ * from that assumed in the definition of struct ethtool_coalesce.
+ * Therefore we do not use any of the adaptive moderation parameters
+ * in it.
+ */
+
 static int efx_ethtool_get_coalesce(struct net_device *net_dev,
                                     struct ethtool_coalesce *coalesce)
 {
         struct efx_nic *efx = netdev_priv(net_dev);
-        struct efx_channel *channel;
-
-        memset(coalesce, 0, sizeof(*coalesce));
-
-        /* Find lowest IRQ moderation across all used TX queues */
-        coalesce->tx_coalesce_usecs_irq = ~((u32) 0);
-        efx_for_each_channel(channel, efx) {
-                if (!efx_channel_has_tx_queues(channel))
-                        continue;
-                if (channel->irq_moderation < coalesce->tx_coalesce_usecs_irq) {
-                        if (channel->channel < efx->n_rx_channels)
-                                coalesce->tx_coalesce_usecs_irq =
-                                        channel->irq_moderation;
-                        else
-                                coalesce->tx_coalesce_usecs_irq = 0;
-                }
-        }
+        unsigned int tx_usecs, rx_usecs;
+        bool rx_adaptive;
 
-        coalesce->use_adaptive_rx_coalesce = efx->irq_rx_adaptive;
-        coalesce->rx_coalesce_usecs_irq = efx->irq_rx_moderation;
+        efx_get_irq_moderation(efx, &tx_usecs, &rx_usecs, &rx_adaptive);
 
-        coalesce->tx_coalesce_usecs_irq *= EFX_IRQ_MOD_RESOLUTION;
-        coalesce->rx_coalesce_usecs_irq *= EFX_IRQ_MOD_RESOLUTION;
+        coalesce->tx_coalesce_usecs_irq = tx_usecs;
+        coalesce->rx_coalesce_usecs_irq = rx_usecs;
+        coalesce->use_adaptive_rx_coalesce = rx_adaptive;
 
         return 0;
 }
 
-/* Set coalescing parameters
- * The difficulties occur for shared channels
- */
 static int efx_ethtool_set_coalesce(struct net_device *net_dev,
                                     struct ethtool_coalesce *coalesce)
 {
@@ -637,20 +634,22 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
                 return -EINVAL;
         }
 
+        efx_get_irq_moderation(efx, &tx_usecs, &rx_usecs, &adaptive);
+
         rx_usecs = coalesce->rx_coalesce_usecs_irq;
-        tx_usecs = coalesce->tx_coalesce_usecs_irq;
         adaptive = coalesce->use_adaptive_rx_coalesce;
 
-        /* If the channel is shared only allow RX parameters to be set */
-        efx_for_each_channel(channel, efx) {
-                if (efx_channel_has_rx_queue(channel) &&
-                    efx_channel_has_tx_queues(channel) &&
-                    tx_usecs) {
-                        netif_err(efx, drv, efx->net_dev, "Channel is shared. "
-                                  "Only RX coalescing may be set\n");
-                        return -EINVAL;
-                }
+        /* If channels are shared, TX IRQ moderation can be quietly
+         * overridden unless it is changed from its old value.
+         */
+        if (efx->tx_channel_offset == 0 &&
+            coalesce->tx_coalesce_usecs_irq != tx_usecs &&
+            coalesce->tx_coalesce_usecs_irq != rx_usecs) {
+                netif_err(efx, drv, efx->net_dev, "Channels are shared. "
+                          "RX and TX IRQ moderation must be equal\n");
+                return -EINVAL;
         }
+        tx_usecs = coalesce->tx_coalesce_usecs_irq;
 
         efx_init_irq_moderation(efx, tx_usecs, rx_usecs, adaptive);
         efx_for_each_channel(channel, efx)