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>

1 files changed, 101 insertions, 30 deletions

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);
 }
 
 /**************************************************************************