tsnep: Throttle interrupts

Without interrupt throttling, iperf server mode generates a CPU load of
100% (A53 1.2GHz). Also the throughput suffers with less than 900Mbit/s
on a 1Gbit/s link. The reason is a high interrupt load with interrupts
every ~20us.

Reduce interrupt load by throttling of interrupts. Interrupt delay
default is 64us. For iperf server mode the CPU load is significantly
reduced to ~20% and the throughput reaches the maximum of 941MBit/s.
Interrupts are generated every ~140us.

RX and TX coalesce can be configured with ethtool. RX coalesce has
priority over TX coalesce if the same interrupt is used.

Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/engleder/tsnep.h b/drivers/net/ethernet/engleder/tsnep.h
index 09a723b..6bb74dd 100644 (file)
--- a/drivers/net/ethernet/engleder/tsnep.h
+++ b/drivers/net/ethernet/engleder/tsnep.h
@@ -132,6 +132,8 @@ struct tsnep_queue {
 
        int irq;
        u32 irq_mask;
+       void __iomem *irq_delay_addr;
+       u8 irq_delay;
 };
 
 struct tsnep_adapter {
@@ -223,5 +225,7 @@ static inline void tsnep_ethtool_self_test(struct net_device *dev,
 #endif /* CONFIG_TSNEP_SELFTESTS */
 
 void tsnep_get_system_time(struct tsnep_adapter *adapter, u64 *time);
+int tsnep_set_irq_coalesce(struct tsnep_queue *queue, u32 usecs);
+u32 tsnep_get_irq_coalesce(struct tsnep_queue *queue);
 
 #endif /* _TSNEP_H */

diff --git a/drivers/net/ethernet/engleder/tsnep_ethtool.c b/drivers/net/ethernet/engleder/tsnep_ethtool.c
index 517ac8d..b97ba35 100644 (file)
--- a/drivers/net/ethernet/engleder/tsnep_ethtool.c
+++ b/drivers/net/ethernet/engleder/tsnep_ethtool.c
@@ -324,7 +324,137 @@ static int tsnep_ethtool_get_ts_info(struct net_device *netdev,
        return 0;
 }
 
+static struct tsnep_queue *tsnep_get_queue_with_tx(struct tsnep_adapter *adapter,
+                                                  int index)
+{
+       int i;
+
+       for (i = 0; i < adapter->num_queues; i++) {
+               if (adapter->queue[i].tx) {
+                       if (index == 0)
+                               return &adapter->queue[i];
+
+                       index--;
+               }
+       }
+
+       return NULL;
+}
+
+static struct tsnep_queue *tsnep_get_queue_with_rx(struct tsnep_adapter *adapter,
+                                                  int index)
+{
+       int i;
+
+       for (i = 0; i < adapter->num_queues; i++) {
+               if (adapter->queue[i].rx) {
+                       if (index == 0)
+                               return &adapter->queue[i];
+
+                       index--;
+               }
+       }
+
+       return NULL;
+}
+
+static int tsnep_ethtool_get_coalesce(struct net_device *netdev,
+                                     struct ethtool_coalesce *ec,
+                                     struct kernel_ethtool_coalesce *kernel_coal,
+                                     struct netlink_ext_ack *extack)
+{
+       struct tsnep_adapter *adapter = netdev_priv(netdev);
+       struct tsnep_queue *queue;
+
+       queue = tsnep_get_queue_with_rx(adapter, 0);
+       if (queue)
+               ec->rx_coalesce_usecs = tsnep_get_irq_coalesce(queue);
+
+       queue = tsnep_get_queue_with_tx(adapter, 0);
+       if (queue)
+               ec->tx_coalesce_usecs = tsnep_get_irq_coalesce(queue);
+
+       return 0;
+}
+
+static int tsnep_ethtool_set_coalesce(struct net_device *netdev,
+                                     struct ethtool_coalesce *ec,
+                                     struct kernel_ethtool_coalesce *kernel_coal,
+                                     struct netlink_ext_ack *extack)
+{
+       struct tsnep_adapter *adapter = netdev_priv(netdev);
+       int i;
+       int retval;
+
+       for (i = 0; i < adapter->num_queues; i++) {
+               /* RX coalesce has priority for queues with TX and RX */
+               if (adapter->queue[i].rx)
+                       retval = tsnep_set_irq_coalesce(&adapter->queue[i],
+                                                       ec->rx_coalesce_usecs);
+               else
+                       retval = tsnep_set_irq_coalesce(&adapter->queue[i],
+                                                       ec->tx_coalesce_usecs);
+               if (retval != 0)
+                       return retval;
+       }
+
+       return 0;
+}
+
+static int tsnep_ethtool_get_per_queue_coalesce(struct net_device *netdev,
+                                               u32 queue,
+                                               struct ethtool_coalesce *ec)
+{
+       struct tsnep_adapter *adapter = netdev_priv(netdev);
+       struct tsnep_queue *queue_with_rx;
+       struct tsnep_queue *queue_with_tx;
+
+       if (queue >= max(adapter->num_tx_queues, adapter->num_rx_queues))
+               return -EINVAL;
+
+       queue_with_rx = tsnep_get_queue_with_rx(adapter, queue);
+       if (queue_with_rx)
+               ec->rx_coalesce_usecs = tsnep_get_irq_coalesce(queue_with_rx);
+
+       queue_with_tx = tsnep_get_queue_with_tx(adapter, queue);
+       if (queue_with_tx)
+               ec->tx_coalesce_usecs = tsnep_get_irq_coalesce(queue_with_tx);
+
+       return 0;
+}
+
+static int tsnep_ethtool_set_per_queue_coalesce(struct net_device *netdev,
+                                               u32 queue,
+                                               struct ethtool_coalesce *ec)
+{
+       struct tsnep_adapter *adapter = netdev_priv(netdev);
+       struct tsnep_queue *queue_with_rx;
+       struct tsnep_queue *queue_with_tx;
+       int retval;
+
+       if (queue >= max(adapter->num_tx_queues, adapter->num_rx_queues))
+               return -EINVAL;
+
+       queue_with_rx = tsnep_get_queue_with_rx(adapter, queue);
+       if (queue_with_rx) {
+               retval = tsnep_set_irq_coalesce(queue_with_rx, ec->rx_coalesce_usecs);
+               if (retval != 0)
+                       return retval;
+       }
+
+       /* RX coalesce has priority for queues with TX and RX */
+       queue_with_tx = tsnep_get_queue_with_tx(adapter, queue);
+       if (queue_with_tx && !queue_with_tx->rx) {
+               retval = tsnep_set_irq_coalesce(queue_with_tx, ec->tx_coalesce_usecs);
+               if (retval != 0)
+                       return retval;
+       }
+
+       return 0;
+}
+
 const struct ethtool_ops tsnep_ethtool_ops = {
+       .supported_coalesce_params = ETHTOOL_COALESCE_USECS,
        .get_drvinfo = tsnep_ethtool_get_drvinfo,
        .get_regs_len = tsnep_ethtool_get_regs_len,
        .get_regs = tsnep_ethtool_get_regs,
@@ -340,6 +470,10 @@ const struct ethtool_ops tsnep_ethtool_ops = {
        .set_rxnfc = tsnep_ethtool_set_rxnfc,
        .get_channels = tsnep_ethtool_get_channels,
        .get_ts_info = tsnep_ethtool_get_ts_info,
+       .get_coalesce = tsnep_ethtool_get_coalesce,
+       .set_coalesce = tsnep_ethtool_set_coalesce,
+       .get_per_queue_coalesce = tsnep_ethtool_get_per_queue_coalesce,
+       .set_per_queue_coalesce = tsnep_ethtool_set_per_queue_coalesce,
        .get_link_ksettings = phy_ethtool_get_link_ksettings,
        .set_link_ksettings = phy_ethtool_set_link_ksettings,
 };

diff --git a/drivers/net/ethernet/engleder/tsnep_hw.h b/drivers/net/ethernet/engleder/tsnep_hw.h
index 315dada..55e1caf 100644 (file)
--- a/drivers/net/ethernet/engleder/tsnep_hw.h
+++ b/drivers/net/ethernet/engleder/tsnep_hw.h
@@ -48,6 +48,13 @@
 #define ECM_COUNTER_LOW 0x0028
 #define ECM_COUNTER_HIGH 0x002C
 
+/* interrupt delay */
+#define ECM_INT_DELAY 0x0030
+#define ECM_INT_DELAY_MASK 0xF0
+#define ECM_INT_DELAY_SHIFT 4
+#define ECM_INT_DELAY_BASE_US 16
+#define ECM_INT_DELAY_OFFSET 1
+
 /* control and status */
 #define ECM_STATUS 0x0080
 #define ECM_LINK_MODE_OFF 0x01000000

diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
index 13d5ff4..5e0d23d 100644 (file)
--- a/drivers/net/ethernet/engleder/tsnep_main.c
+++ b/drivers/net/ethernet/engleder/tsnep_main.c
@@ -39,6 +39,10 @@
 #endif
 #define DMA_ADDR_LOW(dma_addr) ((u32)((dma_addr) & 0xFFFFFFFF))
 
+#define TSNEP_COALESCE_USECS_DEFAULT 64
+#define TSNEP_COALESCE_USECS_MAX     ((ECM_INT_DELAY_MASK >> ECM_INT_DELAY_SHIFT) * \
+                                     ECM_INT_DELAY_BASE_US + ECM_INT_DELAY_BASE_US - 1)
+
 static void tsnep_enable_irq(struct tsnep_adapter *adapter, u32 mask)
 {
        iowrite32(mask, adapter->addr + ECM_INT_ENABLE);
@@ -83,6 +87,33 @@ static irqreturn_t tsnep_irq_txrx(int irq, void *arg)
        return IRQ_HANDLED;
 }
 
+int tsnep_set_irq_coalesce(struct tsnep_queue *queue, u32 usecs)
+{
+       if (usecs > TSNEP_COALESCE_USECS_MAX)
+               return -ERANGE;
+
+       usecs /= ECM_INT_DELAY_BASE_US;
+       usecs <<= ECM_INT_DELAY_SHIFT;
+       usecs &= ECM_INT_DELAY_MASK;
+
+       queue->irq_delay &= ~ECM_INT_DELAY_MASK;
+       queue->irq_delay |= usecs;
+       iowrite8(queue->irq_delay, queue->irq_delay_addr);
+
+       return 0;
+}
+
+u32 tsnep_get_irq_coalesce(struct tsnep_queue *queue)
+{
+       u32 usecs;
+
+       usecs = (queue->irq_delay & ECM_INT_DELAY_MASK);
+       usecs >>= ECM_INT_DELAY_SHIFT;
+       usecs *= ECM_INT_DELAY_BASE_US;
+
+       return usecs;
+}
+
 static int tsnep_mdiobus_read(struct mii_bus *bus, int addr, int regnum)
 {
        struct tsnep_adapter *adapter = bus->priv;
@@ -1371,6 +1402,11 @@ static int tsnep_queue_init(struct tsnep_adapter *adapter, int queue_count)
        adapter->queue[0].tx = &adapter->tx[0];
        adapter->queue[0].rx = &adapter->rx[0];
        adapter->queue[0].irq_mask = irq_mask;
+       adapter->queue[0].irq_delay_addr = adapter->addr + ECM_INT_DELAY;
+       retval = tsnep_set_irq_coalesce(&adapter->queue[0],
+                                       TSNEP_COALESCE_USECS_DEFAULT);
+       if (retval < 0)
+               return retval;
 
        adapter->netdev->irq = adapter->queue[0].irq;
 
@@ -1391,6 +1427,12 @@ static int tsnep_queue_init(struct tsnep_adapter *adapter, int queue_count)
                adapter->queue[i].rx = &adapter->rx[i];
                adapter->queue[i].irq_mask =
                        irq_mask << (ECM_INT_TXRX_SHIFT * i);
+               adapter->queue[i].irq_delay_addr =
+                       adapter->addr + ECM_INT_DELAY + ECM_INT_DELAY_OFFSET * i;
+               retval = tsnep_set_irq_coalesce(&adapter->queue[i],
+                                               TSNEP_COALESCE_USECS_DEFAULT);
+               if (retval < 0)
+                       return retval;
        }
 
        return 0;