sfc: Split MAC stats DMA initiation and completion

From: Steve Hodgson <shodgson@solarflare.com>

Currently we initiate MAC stats DMA and busy-wait for completion when
stats are requested.  We can improve on this with a periodic timer to
initiate and poll for stats, and opportunistically poll when stats are
requested.

Since efx_nic::stats_disable_count and efx_stats_{disable,enable}()
are Falcon-specific, rename them and move them accordingly.

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

9 files changed, 139 insertions, 88 deletions

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 155aa1cca366..41ca5dbb4c44 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -637,6 +637,7 @@ void __efx_reconfigure_port(struct efx_nic *efx)
                 netif_addr_unlock_bh(efx->net_dev);
         }
 
+        falcon_stop_nic_stats(efx);
         falcon_deconfigure_mac_wrapper(efx);
 
         /* Reconfigure the PHY, disabling transmit in mac level loopback. */
@@ -651,6 +652,8 @@ void __efx_reconfigure_port(struct efx_nic *efx)
 
         efx->mac_op->reconfigure(efx);
 
+        falcon_start_nic_stats(efx);
+
         /* Inform kernel of loss/gain of carrier */
         efx_link_status_changed(efx);
         return;
@@ -749,7 +752,6 @@ static int efx_init_port(struct efx_nic *efx)
         efx->mac_op->reconfigure(efx);
 
         efx->port_initialized = true;
-        efx_stats_enable(efx);
 
         mutex_unlock(&efx->mac_lock);
         return 0;
@@ -802,7 +804,6 @@ static void efx_fini_port(struct efx_nic *efx)
         if (!efx->port_initialized)
                 return;
 
-        efx_stats_disable(efx);
         efx->phy_op->fini(efx);
         efx->port_initialized = false;
 
@@ -1158,6 +1159,8 @@ static void efx_start_all(struct efx_nic *efx)
         if (efx->state == STATE_RUNNING)
                 queue_delayed_work(efx->workqueue, &efx->monitor_work,
                                    efx_monitor_interval);
+
+        falcon_start_nic_stats(efx);
 }
 
 /* Flush all delayed work. Should only be called when no more delayed work
@@ -1195,6 +1198,8 @@ static void efx_stop_all(struct efx_nic *efx)
         if (!efx->port_enabled)
                 return;
 
+        falcon_stop_nic_stats(efx);
+
         /* Disable interrupts and wait for ISR to complete */
         falcon_disable_interrupts(efx);
         if (efx->legacy_irq)
@@ -1438,20 +1443,6 @@ static int efx_net_stop(struct net_device *net_dev)
         return 0;
 }
 
-void efx_stats_disable(struct efx_nic *efx)
-{
-        spin_lock(&efx->stats_lock);
-        ++efx->stats_disable_count;
-        spin_unlock(&efx->stats_lock);
-}
-
-void efx_stats_enable(struct efx_nic *efx)
-{
-        spin_lock(&efx->stats_lock);
-        --efx->stats_disable_count;
-        spin_unlock(&efx->stats_lock);
-}
-
 /* Context: process, dev_base_lock or RTNL held, non-blocking. */
 static struct net_device_stats *efx_net_stats(struct net_device *net_dev)
 {
@@ -1459,17 +1450,9 @@ static struct net_device_stats *efx_net_stats(struct net_device *net_dev)
         struct efx_mac_stats *mac_stats = &efx->mac_stats;
         struct net_device_stats *stats = &net_dev->stats;
 
-        /* Update stats if possible, but do not wait if another thread
-         * is updating them or if MAC stats fetches are temporarily
-         * disabled; slightly stale stats are acceptable.
-         */
-        if (!spin_trylock(&efx->stats_lock))
-                return stats;
-        if (!efx->stats_disable_count) {
-                efx->mac_op->update_stats(efx);
-                falcon_update_nic_stats(efx);
-        }
-        spin_unlock(&efx->stats_lock);
+        spin_lock_bh(&efx->stats_lock);
+        falcon_update_nic_stats(efx);
+        spin_unlock_bh(&efx->stats_lock);
 
         stats->rx_packets = mac_stats->rx_packets;
         stats->tx_packets = mac_stats->tx_packets;
@@ -1726,7 +1709,6 @@ void efx_reset_down(struct efx_nic *efx, enum reset_type method,
 {
         EFX_ASSERT_RESET_SERIALISED(efx);
 
-        efx_stats_disable(efx);
         efx_stop_all(efx);
         mutex_lock(&efx->mac_lock);
         mutex_lock(&efx->spi_lock);
@@ -1776,10 +1758,8 @@ int efx_reset_up(struct efx_nic *efx, enum reset_type method,
         mutex_unlock(&efx->spi_lock);
         mutex_unlock(&efx->mac_lock);
 
-        if (ok) {
+        if (ok)
                 efx_start_all(efx);
-                efx_stats_enable(efx);
-        }
         return rc;
 }
 
@@ -1977,7 +1957,6 @@ static int efx_init_struct(struct efx_nic *efx, struct efx_nic_type *type,
         efx->rx_checksum_enabled = true;
         spin_lock_init(&efx->netif_stop_lock);
         spin_lock_init(&efx->stats_lock);
-        efx->stats_disable_count = 1;
         mutex_init(&efx->mac_lock);
         efx->mac_op = &efx_dummy_mac_operations;
         efx->phy_op = &efx_dummy_phy_operations;
@@ -2219,9 +2198,8 @@ static int __devinit efx_pci_probe(struct pci_dev *pci_dev,
                 goto fail4;
         }
 
-        /* Switch to the running state before we expose the device to
-         * the OS.  This is to ensure that the initial gathering of
-         * MAC stats succeeds. */
+        /* Switch to the running state before we expose the device to the OS,
+         * so that dev_open()|efx_start_all() will actually start the device */
         efx->state = STATE_RUNNING;
 
         rc = efx_register_netdev(efx);
diff --git a/drivers/net/sfc/efx.h b/drivers/net/sfc/efx.h
index 7acf82108a4f..01b93f93d316 100644
--- a/drivers/net/sfc/efx.h
+++ b/drivers/net/sfc/efx.h
@@ -60,8 +60,6 @@ extern void efx_process_channel_now(struct efx_channel *channel);
 #define EFX_EVQ_MASK (EFX_EVQ_SIZE - 1)
 
 /* Ports */
-extern void efx_stats_disable(struct efx_nic *efx);
-extern void efx_stats_enable(struct efx_nic *efx);
 extern void efx_reconfigure_port(struct efx_nic *efx);
 extern void __efx_reconfigure_port(struct efx_nic *efx);
 
diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index 9eec88502101..3ab2daff6b48 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -36,8 +36,6 @@
  **************************************************************************
  */
 
-static int disable_dma_stats;
-
 /* This is set to 16 for a good reason.  In summary, if larger than
  * 16, the descriptor cache holds more than a default socket
  * buffer's worth of packets (for UDP we can only have at most one
@@ -1890,7 +1888,7 @@ static int falcon_reset_macs(struct efx_nic *efx)
 
         /* MAC stats will fail whilst the TX fifo is draining. Serialise
          * the drain sequence with the statistics fetch */
-        efx_stats_disable(efx);
+        falcon_stop_nic_stats(efx);
 
         efx_reado(efx, &reg, FR_AB_MAC_CTRL);
         EFX_SET_OWORD_FIELD(reg, FRF_BB_TXFIFO_DRAIN_EN, 1);
@@ -1920,13 +1918,13 @@ static int falcon_reset_macs(struct efx_nic *efx)
                 udelay(10);
         }
 
-        efx_stats_enable(efx);
-
         /* If we've reset the EM block and the link is up, then
          * we'll have to kick the XAUI link so the PHY can recover */
         if (efx->link_state.up && EFX_IS10G(efx) && EFX_WORKAROUND_5147(efx))
                 falcon_reset_xaui(efx);
 
+        falcon_start_nic_stats(efx);
+
         return 0;
 }
 
@@ -2010,25 +2008,19 @@ void falcon_reconfigure_mac_wrapper(struct efx_nic *efx)
         efx_writeo(efx, &reg, FR_AZ_RX_CFG);
 }
 
-int falcon_dma_stats(struct efx_nic *efx, unsigned int done_offset)
+static void falcon_stats_request(struct efx_nic *efx)
 {
+        struct falcon_nic_data *nic_data = efx->nic_data;
         efx_oword_t reg;
-        u32 *dma_done;
-        int i;
 
-        if (disable_dma_stats)
-                return 0;
+        WARN_ON(nic_data->stats_pending);
+        WARN_ON(nic_data->stats_disable_count);
 
-        /* Statistics fetch will fail if the MAC is in TX drain */
-        if (falcon_rev(efx) >= FALCON_REV_B0) {
-                efx_oword_t temp;
-                efx_reado(efx, &temp, FR_AB_MAC_CTRL);
-                if (EFX_OWORD_FIELD(temp, FRF_BB_TXFIFO_DRAIN_EN))
-                        return 0;
-        }
+        if (nic_data->stats_dma_done == NULL)
+                return; /* no mac selected */
 
-        dma_done = (efx->stats_buffer.addr + done_offset);
-        *dma_done = FALCON_STATS_NOT_DONE;
+        *nic_data->stats_dma_done = FALCON_STATS_NOT_DONE;
+        nic_data->stats_pending = true;
         wmb(); /* ensure done flag is clear */
 
         /* Initiate DMA transfer of stats */
@@ -2038,17 +2030,37 @@ int falcon_dma_stats(struct efx_nic *efx, unsigned int done_offset)
                              efx->stats_buffer.dma_addr);
         efx_writeo(efx, &reg, FR_AB_MAC_STAT_DMA);
 
-        /* Wait for transfer to complete */
-        for (i = 0; i < 400; i++) {
-                if (*(volatile u32 *)dma_done == FALCON_STATS_DONE) {
-                        rmb(); /* Ensure the stats are valid. */
-                        return 0;
-                }
-                udelay(10);
+        mod_timer(&nic_data->stats_timer, round_jiffies_up(jiffies + HZ / 2));
+}
+
+static void falcon_stats_complete(struct efx_nic *efx)
+{
+        struct falcon_nic_data *nic_data = efx->nic_data;
+
+        if (!nic_data->stats_pending)
+                return;
+
+        nic_data->stats_pending = 0;
+        if (*nic_data->stats_dma_done == FALCON_STATS_DONE) {
+                rmb(); /* read the done flag before the stats */
+                efx->mac_op->update_stats(efx);
+        } else {
+                EFX_ERR(efx, "timed out waiting for statistics\n");
         }
+}
 
-        EFX_ERR(efx, "timed out waiting for statistics\n");
-        return -ETIMEDOUT;
+static void falcon_stats_timer_func(unsigned long context)
+{
+        struct efx_nic *efx = (struct efx_nic *)context;
+        struct falcon_nic_data *nic_data = efx->nic_data;
+
+        spin_lock(&efx->stats_lock);
+
+        falcon_stats_complete(efx);
+        if (nic_data->stats_disable_count == 0)
+                falcon_stats_request(efx);
+
+        spin_unlock(&efx->stats_lock);
 }
 
 /**************************************************************************
@@ -2206,10 +2218,12 @@ static void falcon_clock_mac(struct efx_nic *efx)
 int falcon_switch_mac(struct efx_nic *efx)
 {
         struct efx_mac_operations *old_mac_op = efx->mac_op;
+        struct falcon_nic_data *nic_data = efx->nic_data;
+        unsigned int stats_done_offset;
         int rc = 0;
 
         /* Don't try to fetch MAC stats while we're switching MACs */
-        efx_stats_disable(efx);
+        falcon_stop_nic_stats(efx);
 
         /* Internal loopbacks override the phy speed setting */
         if (efx->loopback_mode == LOOPBACK_GMAC) {
@@ -2224,6 +2238,12 @@ int falcon_switch_mac(struct efx_nic *efx)
         efx->mac_op = (EFX_IS10G(efx) ?
                        &falcon_xmac_operations : &falcon_gmac_operations);
 
+        if (EFX_IS10G(efx))
+                stats_done_offset = XgDmaDone_offset;
+        else
+                stats_done_offset = GDmaDone_offset;
+        nic_data->stats_dma_done = efx->stats_buffer.addr + stats_done_offset;
+
         if (old_mac_op == efx->mac_op)
                 goto out;
 
@@ -2235,7 +2255,7 @@ int falcon_switch_mac(struct efx_nic *efx)
 
         rc = falcon_reset_macs(efx);
 out:
-        efx_stats_enable(efx);
+        falcon_start_nic_stats(efx);
         return rc;
 }
 
@@ -2900,6 +2920,10 @@ int falcon_probe_nic(struct efx_nic *efx)
                 goto fail6;
         }
 
+        nic_data->stats_disable_count = 1;
+        setup_timer(&nic_data->stats_timer, &falcon_stats_timer_func,
+                    (unsigned long)efx);
+
         return 0;
 
  fail6:
@@ -3125,11 +3149,58 @@ void falcon_remove_nic(struct efx_nic *efx)
 
 void falcon_update_nic_stats(struct efx_nic *efx)
 {
+        struct falcon_nic_data *nic_data = efx->nic_data;
         efx_oword_t cnt;
 
+        if (nic_data->stats_disable_count)
+                return;
+
         efx_reado(efx, &cnt, FR_AZ_RX_NODESC_DROP);
         efx->n_rx_nodesc_drop_cnt +=
                 EFX_OWORD_FIELD(cnt, FRF_AB_RX_NODESC_DROP_CNT);
+
+        if (nic_data->stats_pending &&
+            *nic_data->stats_dma_done == FALCON_STATS_DONE) {
+                nic_data->stats_pending = false;
+                rmb(); /* read the done flag before the stats */
+                efx->mac_op->update_stats(efx);
+        }
+}
+
+void falcon_start_nic_stats(struct efx_nic *efx)
+{
+        struct falcon_nic_data *nic_data = efx->nic_data;
+
+        spin_lock_bh(&efx->stats_lock);
+        if (--nic_data->stats_disable_count == 0)
+                falcon_stats_request(efx);
+        spin_unlock_bh(&efx->stats_lock);
+}
+
+void falcon_stop_nic_stats(struct efx_nic *efx)
+{
+        struct falcon_nic_data *nic_data = efx->nic_data;
+        int i;
+
+        might_sleep();
+
+        spin_lock_bh(&efx->stats_lock);
+        ++nic_data->stats_disable_count;
+        spin_unlock_bh(&efx->stats_lock);
+
+        del_timer_sync(&nic_data->stats_timer);
+
+        /* Wait enough time for the most recent transfer to
+         * complete. */
+        for (i = 0; i < 4 && nic_data->stats_pending; i++) {
+                if (*nic_data->stats_dma_done == FALCON_STATS_DONE)
+                        break;
+                msleep(1);
+        }
+
+        spin_lock_bh(&efx->stats_lock);
+        falcon_stats_complete(efx);
+        spin_unlock_bh(&efx->stats_lock);
 }
 
 /**************************************************************************
diff --git a/drivers/net/sfc/falcon.h b/drivers/net/sfc/falcon.h
index b331889ca46c..61fab0a00cc3 100644
--- a/drivers/net/sfc/falcon.h
+++ b/drivers/net/sfc/falcon.h
@@ -75,10 +75,18 @@ struct falcon_board {
  * struct falcon_nic_data - Falcon NIC state
  * @pci_dev2: Secondary function of Falcon A
  * @board: Board state and functions
+ * @stats_disable_count: Nest count for disabling statistics fetches
+ * @stats_pending: Is there a pending DMA of MAC statistics.
+ * @stats_timer: A timer for regularly fetching MAC statistics.
+ * @stats_dma_done: Pointer to the flag which indicates DMA completion.
  */
 struct falcon_nic_data {
         struct pci_dev *pci_dev2;
         struct falcon_board board;
+        unsigned int stats_disable_count;
+        bool stats_pending;
+        struct timer_list stats_timer;
+        u32 *stats_dma_done;
 };
 
 static inline struct falcon_board *falcon_board(struct efx_nic *efx)
@@ -128,8 +136,6 @@ extern void falcon_remove_port(struct efx_nic *efx);
 /* MAC/PHY */
 extern int falcon_switch_mac(struct efx_nic *efx);
 extern bool falcon_xaui_link_ok(struct efx_nic *efx);
-extern int falcon_dma_stats(struct efx_nic *efx,
-                            unsigned int done_offset);
 extern void falcon_drain_tx_fifo(struct efx_nic *efx);
 extern void falcon_deconfigure_mac_wrapper(struct efx_nic *efx);
 extern void falcon_reconfigure_mac_wrapper(struct efx_nic *efx);
@@ -154,6 +160,8 @@ extern int falcon_flush_queues(struct efx_nic *efx);
 extern int falcon_reset_hw(struct efx_nic *efx, enum reset_type method);
 extern void falcon_remove_nic(struct efx_nic *efx);
 extern void falcon_update_nic_stats(struct efx_nic *efx);
+extern void falcon_start_nic_stats(struct efx_nic *efx);
+extern void falcon_stop_nic_stats(struct efx_nic *efx);
 extern void falcon_set_multicast_hash(struct efx_nic *efx);
 extern int falcon_reset_xaui(struct efx_nic *efx);
 
diff --git a/drivers/net/sfc/falcon_boards.c b/drivers/net/sfc/falcon_boards.c
index ac1258ea677c..72d1c7834e6b 100644
--- a/drivers/net/sfc/falcon_boards.c
+++ b/drivers/net/sfc/falcon_boards.c
@@ -347,14 +347,14 @@ static ssize_t set_phy_flash_cfg(struct device *dev,
                  * MAC stats accordingly. */
                 efx->phy_mode = new_mode;
                 if (new_mode & PHY_MODE_SPECIAL)
-                        efx_stats_disable(efx);
+                        falcon_stop_nic_stats(efx);
                 if (falcon_board(efx)->type->id == FALCON_BOARD_SFE4001)
                         err = sfe4001_poweron(efx);
                 else
                         err = sfn4111t_reset(efx);
                 efx_reconfigure_port(efx);
                 if (!(new_mode & PHY_MODE_SPECIAL))
-                        efx_stats_enable(efx);
+                        falcon_start_nic_stats(efx);
         }
         rtnl_unlock();
 
@@ -441,7 +441,7 @@ static int sfe4001_init(struct efx_nic *efx)
         if (efx->phy_mode & PHY_MODE_SPECIAL) {
                 /* PHY won't generate a 156.25 MHz clock and MAC stats fetch
                  * will fail. */
-                efx_stats_disable(efx);
+                falcon_stop_nic_stats(efx);
         }
         rc = sfe4001_poweron(efx);
         if (rc)
@@ -504,7 +504,7 @@ static void sfn4111t_init_phy(struct efx_nic *efx)
                         return;
 
                 efx->phy_mode = PHY_MODE_SPECIAL;
-                efx_stats_disable(efx);
+                falcon_stop_nic_stats(efx);
         }
 
         sfn4111t_reset(efx);
@@ -531,7 +531,7 @@ static int sfn4111t_init(struct efx_nic *efx)
         if (efx->phy_mode & PHY_MODE_SPECIAL)
                 /* PHY may not generate a 156.25 MHz clock and MAC
                  * stats fetch will fail. */
-                efx_stats_disable(efx);
+                falcon_stop_nic_stats(efx);
 
         return 0;
 
diff --git a/drivers/net/sfc/falcon_gmac.c b/drivers/net/sfc/falcon_gmac.c
index 967f3fb397c9..2aeb3fc02786 100644
--- a/drivers/net/sfc/falcon_gmac.c
+++ b/drivers/net/sfc/falcon_gmac.c
@@ -130,11 +130,6 @@ static void falcon_update_stats_gmac(struct efx_nic *efx)
         struct efx_mac_stats *mac_stats = &efx->mac_stats;
         unsigned long old_rx_pause, old_tx_pause;
         unsigned long new_rx_pause, new_tx_pause;
-        int rc;
-
-        rc = falcon_dma_stats(efx, GDmaDone_offset);
-        if (rc)
-                return;
 
         /* Pause frames are erroneously counted as errors (SFC bug 3269) */
         old_rx_pause = mac_stats->rx_pause;
diff --git a/drivers/net/sfc/falcon_xmac.c b/drivers/net/sfc/falcon_xmac.c
index cf24513900e7..e57545de60ff 100644
--- a/drivers/net/sfc/falcon_xmac.c
+++ b/drivers/net/sfc/falcon_xmac.c
@@ -60,9 +60,13 @@ static void falcon_setup_xaui(struct efx_nic *efx)
 
 int falcon_reset_xaui(struct efx_nic *efx)
 {
+        struct falcon_nic_data *nic_data = efx->nic_data;
         efx_oword_t reg;
         int count;
 
+        /* Don't fetch MAC statistics over an XMAC reset */
+        WARN_ON(nic_data->stats_disable_count == 0);
+
         /* Start reset sequence */
         EFX_POPULATE_OWORD_1(reg, FRF_AB_XX_RST_XX_EN, 1);
         efx_writeo(efx, &reg, FR_AB_XX_PWR_RST);
@@ -250,6 +254,8 @@ static void falcon_check_xaui_link_up(struct efx_nic *efx, int tries)
                 /* XAUI link is expected to be down */
                 return;
 
+        falcon_stop_nic_stats(efx);
+
         while (!efx->mac_up && tries) {
                 EFX_LOG(efx, "bashing xaui\n");
                 falcon_reset_xaui(efx);
@@ -258,6 +264,8 @@ static void falcon_check_xaui_link_up(struct efx_nic *efx, int tries)
                 efx->mac_up = falcon_xaui_link_ok(efx);
                 --tries;
         }
+
+        falcon_start_nic_stats(efx);
 }
 
 static void falcon_reconfigure_xmac(struct efx_nic *efx)
@@ -276,11 +284,6 @@ static void falcon_reconfigure_xmac(struct efx_nic *efx)
 static void falcon_update_stats_xmac(struct efx_nic *efx)
 {
         struct efx_mac_stats *mac_stats = &efx->mac_stats;
-        int rc;
-
-        rc = falcon_dma_stats(efx, XgDmaDone_offset);
-        if (rc)
-                return;
 
         /* Update MAC stats from DMAed values */
         FALCON_STAT(efx, XgRxOctets, rx_bytes);
diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index d0755ab056fe..262aeabdcab7 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -717,7 +717,6 @@ union efx_multicast_hash {
  *      &struct net_device_stats.
  * @stats_buffer: DMA buffer for statistics
  * @stats_lock: Statistics update lock. Serialises statistics fetches
- * @stats_disable_count: Nest count for disabling statistics fetches
  * @mac_op: MAC interface
  * @mac_address: Permanent MAC address
  * @phy_type: PHY type
@@ -799,7 +798,6 @@ struct efx_nic {
         struct efx_mac_stats mac_stats;
         struct efx_buffer stats_buffer;
         spinlock_t stats_lock;
-        unsigned int stats_disable_count;
 
         struct efx_mac_operations *mac_op;
         unsigned char mac_address[ETH_ALEN];
diff --git a/drivers/net/sfc/tenxpress.c b/drivers/net/sfc/tenxpress.c
index a95402d601c7..e6232fe26072 100644
--- a/drivers/net/sfc/tenxpress.c
+++ b/drivers/net/sfc/tenxpress.c
@@ -374,7 +374,7 @@ static int tenxpress_special_reset(struct efx_nic *efx)
         /* The XGMAC clock is driven from the SFC7101/SFT9001 312MHz clock, so
          * a special software reset can glitch the XGMAC sufficiently for stats
          * requests to fail. */
-        efx_stats_disable(efx);
+        falcon_stop_nic_stats(efx);
 
         /* Initiate reset */
         reg = efx_mdio_read(efx, MDIO_MMD_PMAPMD, PMA_PMD_XCONTROL_REG);
@@ -396,7 +396,7 @@ static int tenxpress_special_reset(struct efx_nic *efx)
         /* Wait for the XGXS state machine to churn */
         mdelay(10);
 out:
-        efx_stats_enable(efx);
+        falcon_start_nic_stats(efx);
         return rc;
 }