sfc: Maintain interrupt moderation values in ticks, not microseconds

This simplifies the implementation a lot.

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

4 files changed, 28 insertions, 34 deletions

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 862e4832f614..30951fb3d20f 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -228,26 +228,20 @@ static int efx_poll(struct napi_struct *napi, int budget)
                 if (channel->used_flags & EFX_USED_BY_RX &&
                     efx->irq_rx_adaptive &&
                     unlikely(++channel->irq_count == 1000)) {
-                        unsigned old_irq_moderation = channel->irq_moderation;
-
                         if (unlikely(channel->irq_mod_score <
                                      irq_adapt_low_thresh)) {
-                                channel->irq_moderation =
-                                        max_t(int,
-                                              channel->irq_moderation -
-                                              FALCON_IRQ_MOD_RESOLUTION,
-                                              FALCON_IRQ_MOD_RESOLUTION);
+                                if (channel->irq_moderation > 1) {
+                                        channel->irq_moderation -= 1;
+                                        falcon_set_int_moderation(channel);
+                                }
                         } else if (unlikely(channel->irq_mod_score >
                                             irq_adapt_high_thresh)) {
-                                channel->irq_moderation =
-                                        min(channel->irq_moderation +
-                                            FALCON_IRQ_MOD_RESOLUTION,
-                                            efx->irq_rx_moderation);
+                                if (channel->irq_moderation <
+                                    efx->irq_rx_moderation) {
+                                        channel->irq_moderation += 1;
+                                        falcon_set_int_moderation(channel);
+                                }
                         }
-
-                        if (channel->irq_moderation != old_irq_moderation)
-                                falcon_set_int_moderation(channel);
-
                         channel->irq_count = 0;
                         channel->irq_mod_score = 0;
                 }
@@ -1220,22 +1214,33 @@ void efx_flush_queues(struct efx_nic *efx)
  *
  **************************************************************************/
 
+static unsigned irq_mod_ticks(int usecs, int resolution)
+{
+        if (usecs <= 0)
+                return 0; /* cannot receive interrupts ahead of time :-) */
+        if (usecs < resolution)
+                return 1; /* never round down to 0 */
+        return usecs / resolution;
+}
+
 /* Set interrupt moderation parameters */
 void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs, int rx_usecs,
                              bool rx_adaptive)
 {
         struct efx_tx_queue *tx_queue;
         struct efx_rx_queue *rx_queue;
+        unsigned tx_ticks = irq_mod_ticks(tx_usecs, FALCON_IRQ_MOD_RESOLUTION);
+        unsigned rx_ticks = irq_mod_ticks(rx_usecs, FALCON_IRQ_MOD_RESOLUTION);
 
         EFX_ASSERT_RESET_SERIALISED(efx);
 
         efx_for_each_tx_queue(tx_queue, efx)
-                tx_queue->channel->irq_moderation = tx_usecs;
+                tx_queue->channel->irq_moderation = tx_ticks;
 
         efx->irq_rx_adaptive = rx_adaptive;
-        efx->irq_rx_moderation = rx_usecs;
+        efx->irq_rx_moderation = rx_ticks;
         efx_for_each_rx_queue(rx_queue, efx)
-                rx_queue->channel->irq_moderation = rx_usecs;
+                rx_queue->channel->irq_moderation = rx_ticks;
 }
 
 /**************************************************************************
diff --git a/drivers/net/sfc/ethtool.c b/drivers/net/sfc/ethtool.c
index 45018f283ffa..a313b61c8ff4 100644
--- a/drivers/net/sfc/ethtool.c
+++ b/drivers/net/sfc/ethtool.c
@@ -618,6 +618,9 @@ static int efx_ethtool_get_coalesce(struct net_device *net_dev,
         coalesce->use_adaptive_rx_coalesce = efx->irq_rx_adaptive;
         coalesce->rx_coalesce_usecs_irq = efx->irq_rx_moderation;
 
+        coalesce->tx_coalesce_usecs_irq *= FALCON_IRQ_MOD_RESOLUTION;
+        coalesce->rx_coalesce_usecs_irq *= FALCON_IRQ_MOD_RESOLUTION;
+
         return 0;
 }
 
@@ -656,11 +659,6 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
         }
 
         efx_init_irq_moderation(efx, tx_usecs, rx_usecs, adaptive);
-
-        /* Reset channel to pick up new moderation value.  Note that
-         * this may change the value of the irq_moderation field
-         * (e.g. to allow for hardware timer granularity).
-         */
         efx_for_each_channel(channel, efx)
                 falcon_set_int_moderation(channel);
 
diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index 1582df7aba7b..e3c33fa06c86 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -1063,20 +1063,11 @@ void falcon_set_int_moderation(struct efx_channel *channel)
 
         /* Set timer register */
         if (channel->irq_moderation) {
-                /* Round to resolution supported by hardware.  The value we
-                 * program is based at 0.  So actual interrupt moderation
-                 * achieved is ((x + 1) * res).
-                 */
-                channel->irq_moderation -= (channel->irq_moderation %
-                                            FALCON_IRQ_MOD_RESOLUTION);
-                if (channel->irq_moderation < FALCON_IRQ_MOD_RESOLUTION)
-                        channel->irq_moderation = FALCON_IRQ_MOD_RESOLUTION;
                 EFX_POPULATE_DWORD_2(timer_cmd,
                                      FRF_AB_TC_TIMER_MODE,
                                      FFE_BB_TIMER_MODE_INT_HLDOFF,
                                      FRF_AB_TC_TIMER_VAL,
-                                     channel->irq_moderation /
-                                     FALCON_IRQ_MOD_RESOLUTION - 1);
+                                     channel->irq_moderation - 1);
         } else {
                 EFX_POPULATE_DWORD_2(timer_cmd,
                                      FRF_AB_TC_TIMER_MODE,
diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index 25b793327c1b..c8b6998d7fc7 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -327,7 +327,7 @@ enum efx_rx_alloc_method {
  * @used_flags: Channel is used by net driver
  * @enabled: Channel enabled indicator
  * @irq: IRQ number (MSI and MSI-X only)
- * @irq_moderation: IRQ moderation value (in us)
+ * @irq_moderation: IRQ moderation value (in hardware ticks)
  * @napi_dev: Net device used with NAPI
  * @napi_str: NAPI control structure
  * @reset_work: Scheduled reset work thread