sfc: Correct RX dropped count for drops while interface is down

We don't directly control RX ingress on Siena or any later
controllers, and so we cannot prevent packets from entering the RX
datapath while the RX queues are not set up.  This results in
the hardware incrementing RX_NODESC_DROP_CNT, but it's not an
error and we should not include it in error stats.

When bringing an interface up or down, pull (or wait for) stats and
count the number of packets that were dropped while the interface was
down.  Subtract this from the reported RX dropped count.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 38 insertions, 11 deletions

diff --git a/drivers/net/ethernet/sfc/mcdi_port.c b/drivers/net/ethernet/sfc/mcdi_port.c
index 7b6be61d549f..7288aefc2877 100644
--- a/drivers/net/ethernet/sfc/mcdi_port.c
+++ b/drivers/net/ethernet/sfc/mcdi_port.c
@@ -927,12 +927,23 @@ bool efx_mcdi_mac_check_fault(struct efx_nic *efx)
 	return MCDI_DWORD(outbuf, GET_LINK_OUT_MAC_FAULT) != 0;
 }
 
-static int efx_mcdi_mac_stats(struct efx_nic *efx, dma_addr_t dma_addr,
-			      u32 dma_len, int enable, int clear)
+enum efx_stats_action {
+	EFX_STATS_ENABLE,
+	EFX_STATS_DISABLE,
+	EFX_STATS_PULL,
+};
+
+static int efx_mcdi_mac_stats(struct efx_nic *efx,
+			      enum efx_stats_action action, int clear)
 {
 	MCDI_DECLARE_BUF(inbuf, MC_CMD_MAC_STATS_IN_LEN);
 	int rc;
-	int period = enable ? 1000 : 0;
+	int change = action == EFX_STATS_PULL ? 0 : 1;
+	int enable = action == EFX_STATS_ENABLE ? 1 : 0;
+	int period = action == EFX_STATS_ENABLE ? 1000 : 0;
+	dma_addr_t dma_addr = efx->stats_buffer.dma_addr;
+	u32 dma_len = action != EFX_STATS_DISABLE ?
+		MC_CMD_MAC_NSTATS * sizeof(u64) : 0;
 
 	BUILD_BUG_ON(MC_CMD_MAC_STATS_OUT_DMA_LEN != 0);
 
@@ -940,8 +951,8 @@ static int efx_mcdi_mac_stats(struct efx_nic *efx, dma_addr_t dma_addr,
 	MCDI_POPULATE_DWORD_7(inbuf, MAC_STATS_IN_CMD,
 			      MAC_STATS_IN_DMA, !!enable,
 			      MAC_STATS_IN_CLEAR, clear,
-			      MAC_STATS_IN_PERIODIC_CHANGE, 1,
-			      MAC_STATS_IN_PERIODIC_ENABLE, !!enable,
+			      MAC_STATS_IN_PERIODIC_CHANGE, change,
+			      MAC_STATS_IN_PERIODIC_ENABLE, enable,
 			      MAC_STATS_IN_PERIODIC_CLEAR, 0,
 			      MAC_STATS_IN_PERIODIC_NOEVENT, 1,
 			      MAC_STATS_IN_PERIOD_MS, period);
@@ -955,8 +966,8 @@ static int efx_mcdi_mac_stats(struct efx_nic *efx, dma_addr_t dma_addr,
 	return 0;
 
 fail:
-	netif_err(efx, hw, efx->net_dev, "%s: %s failed rc=%d\n",
-		  __func__, enable ? "enable" : "disable", rc);
+	netif_err(efx, hw, efx->net_dev, "%s: action %d failed rc=%d\n",
+		  __func__, action, rc);
 	return rc;
 }
 
@@ -966,13 +977,29 @@ void efx_mcdi_mac_start_stats(struct efx_nic *efx)
 
 	dma_stats[MC_CMD_MAC_GENERATION_END] = EFX_MC_STATS_GENERATION_INVALID;
 
-	efx_mcdi_mac_stats(efx, efx->stats_buffer.dma_addr,
-			   MC_CMD_MAC_NSTATS * sizeof(u64), 1, 0);
+	efx_mcdi_mac_stats(efx, EFX_STATS_ENABLE, 0);
 }
 
 void efx_mcdi_mac_stop_stats(struct efx_nic *efx)
 {
-	efx_mcdi_mac_stats(efx, efx->stats_buffer.dma_addr, 0, 0, 0);
+	efx_mcdi_mac_stats(efx, EFX_STATS_DISABLE, 0);
+}
+
+#define EFX_MAC_STATS_WAIT_US 100
+#define EFX_MAC_STATS_WAIT_ATTEMPTS 10
+
+void efx_mcdi_mac_pull_stats(struct efx_nic *efx)
+{
+	__le64 *dma_stats = efx->stats_buffer.addr;
+	int attempts = EFX_MAC_STATS_WAIT_ATTEMPTS;
+
+	dma_stats[MC_CMD_MAC_GENERATION_END] = EFX_MC_STATS_GENERATION_INVALID;
+	efx_mcdi_mac_stats(efx, EFX_STATS_PULL, 0);
+
+	while (dma_stats[MC_CMD_MAC_GENERATION_END] ==
+				EFX_MC_STATS_GENERATION_INVALID &&
+			attempts-- != 0)
+		udelay(EFX_MAC_STATS_WAIT_US);
 }
 
 int efx_mcdi_port_probe(struct efx_nic *efx)
@@ -1003,7 +1030,7 @@ int efx_mcdi_port_probe(struct efx_nic *efx)
 		  efx->stats_buffer.addr,
 		  (u64)virt_to_phys(efx->stats_buffer.addr));
 
-	efx_mcdi_mac_stats(efx, efx->stats_buffer.dma_addr, 0, 0, 1);
+	efx_mcdi_mac_stats(efx, EFX_STATS_DISABLE, 1);
 
 	return 0;
 }