nfp: prevent dropped counter increment during probe

The dev_rx_discards counter will increment by one when an interface is
toggled up and down. The main reason is that the driver first sends a
`NFP_NET_CFG_CTRL_ENABLE` configuration packet to the NIC to perform port
initialisation when an interface is set up. But there is a race between
physical link up and free list queue initialization which may lead to the
configuration packet being discarded.

To address this problem a new bit NFP_NET_CFG_CTRL_FREELIST_EN is added to
perform free list initialisation on the NIC. The FREELIST_EN should be sent
in advance to initialize free list queue. When a port is set to down,
FREELIST_EN should be sent after CTRL_ENABLE to avoid packet discards.

Signed-off-by: Ziyang Chen <ziyang.chen@corigine.com>
Acked-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Link: https://lore.kernel.org/r/20230712123551.13858-1-louis.peens@corigine.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -924,7 +924,7 @@ static void nfp_net_write_mac_addr(struct nfp_net *nn, const u8 *addr)
  */
 static void nfp_net_clear_config_and_disable(struct nfp_net *nn)
 {
-	u32 new_ctrl, update;
+	u32 new_ctrl, new_ctrl_w1, update;
 	unsigned int r;
 	int err;
 
@@ -937,14 +937,29 @@ static void nfp_net_clear_config_and_disable(struct nfp_net *nn)
 	if (nn->cap & NFP_NET_CFG_CTRL_RINGCFG)
 		new_ctrl &= ~NFP_NET_CFG_CTRL_RINGCFG;
 
-	nn_writeq(nn, NFP_NET_CFG_TXRS_ENABLE, 0);
-	nn_writeq(nn, NFP_NET_CFG_RXRS_ENABLE, 0);
+	if (!(nn->cap_w1 & NFP_NET_CFG_CTRL_FREELIST_EN)) {
+		nn_writeq(nn, NFP_NET_CFG_TXRS_ENABLE, 0);
+		nn_writeq(nn, NFP_NET_CFG_RXRS_ENABLE, 0);
+	}
 
 	nn_writel(nn, NFP_NET_CFG_CTRL, new_ctrl);
 	err = nfp_net_reconfig(nn, update);
 	if (err)
 		nn_err(nn, "Could not disable device: %d\n", err);
 
+	if (nn->cap_w1 & NFP_NET_CFG_CTRL_FREELIST_EN) {
+		new_ctrl_w1 = nn->dp.ctrl_w1;
+		new_ctrl_w1 &= ~NFP_NET_CFG_CTRL_FREELIST_EN;
+		nn_writeq(nn, NFP_NET_CFG_TXRS_ENABLE, 0);
+		nn_writeq(nn, NFP_NET_CFG_RXRS_ENABLE, 0);
+
+		nn_writel(nn, NFP_NET_CFG_CTRL_WORD1, new_ctrl_w1);
+		err = nfp_net_reconfig(nn, update);
+		if (err)
+			nn_err(nn, "Could not disable FREELIST_EN: %d\n", err);
+		nn->dp.ctrl_w1 = new_ctrl_w1;
+	}
+
 	for (r = 0; r < nn->dp.num_rx_rings; r++) {
 		nfp_net_rx_ring_reset(&nn->dp.rx_rings[r]);
 		if (nfp_net_has_xsk_pool_slow(&nn->dp, nn->dp.rx_rings[r].idx))
@@ -964,11 +979,12 @@ static void nfp_net_clear_config_and_disable(struct nfp_net *nn)
  */
 static int nfp_net_set_config_and_enable(struct nfp_net *nn)
 {
-	u32 bufsz, new_ctrl, update = 0;
+	u32 bufsz, new_ctrl, new_ctrl_w1, update = 0;
 	unsigned int r;
 	int err;
 
 	new_ctrl = nn->dp.ctrl;
+	new_ctrl_w1 = nn->dp.ctrl_w1;
 
 	if (nn->dp.ctrl & NFP_NET_CFG_CTRL_RSS_ANY) {
 		nfp_net_rss_write_key(nn);
@@ -1001,27 +1017,51 @@ static int nfp_net_set_config_and_enable(struct nfp_net *nn)
 	bufsz = nn->dp.fl_bufsz - nn->dp.rx_dma_off - NFP_NET_RX_BUF_NON_DATA;
 	nn_writel(nn, NFP_NET_CFG_FLBUFSZ, bufsz);
 
-	/* Enable device */
-	new_ctrl |= NFP_NET_CFG_CTRL_ENABLE;
+	/* Enable device
+	 * Step 1: Replace the CTRL_ENABLE by NFP_NET_CFG_CTRL_FREELIST_EN if
+	 * FREELIST_EN exits.
+	 */
+	if (nn->cap_w1 & NFP_NET_CFG_CTRL_FREELIST_EN)
+		new_ctrl_w1 |= NFP_NET_CFG_CTRL_FREELIST_EN;
+	else
+		new_ctrl |= NFP_NET_CFG_CTRL_ENABLE;
 	update |= NFP_NET_CFG_UPDATE_GEN;
 	update |= NFP_NET_CFG_UPDATE_MSIX;
 	update |= NFP_NET_CFG_UPDATE_RING;
 	if (nn->cap & NFP_NET_CFG_CTRL_RINGCFG)
 		new_ctrl |= NFP_NET_CFG_CTRL_RINGCFG;
 
+	/* Step 2: Send the configuration and write the freelist.
+	 * - The freelist only need to be written once.
+	 */
 	nn_writel(nn, NFP_NET_CFG_CTRL, new_ctrl);
-	nn_writel(nn, NFP_NET_CFG_CTRL_WORD1, nn->dp.ctrl_w1);
+	nn_writel(nn, NFP_NET_CFG_CTRL_WORD1, new_ctrl_w1);
 	err = nfp_net_reconfig(nn, update);
 	if (err) {
 		nfp_net_clear_config_and_disable(nn);
 		return err;
 	}
 
 	nn->dp.ctrl = new_ctrl;
+	nn->dp.ctrl_w1 = new_ctrl_w1;
 
 	for (r = 0; r < nn->dp.num_rx_rings; r++)
 		nfp_net_rx_ring_fill_freelist(&nn->dp, &nn->dp.rx_rings[r]);
 
+	/* Step 3: Do the NFP_NET_CFG_CTRL_ENABLE. Send the configuration.
+	 */
+	if (nn->cap_w1 & NFP_NET_CFG_CTRL_FREELIST_EN) {
+		new_ctrl |= NFP_NET_CFG_CTRL_ENABLE;
+		nn_writel(nn, NFP_NET_CFG_CTRL, new_ctrl);
+
+		err = nfp_net_reconfig(nn, update);
+		if (err) {
+			nfp_net_clear_config_and_disable(nn);
+			return err;
+		}
+		nn->dp.ctrl = new_ctrl;
+	}
+
 	return 0;
 }
 

drivers/net/ethernet/netronome/nfp/nfp_net_ctrl.h

@@ -268,6 +268,7 @@
 #define   NFP_NET_CFG_CTRL_PKT_TYPE	  (0x1 << 0) /* Pkttype offload */
 #define   NFP_NET_CFG_CTRL_IPSEC	  (0x1 << 1) /* IPsec offload */
 #define   NFP_NET_CFG_CTRL_MCAST_FILTER	  (0x1 << 2) /* Multicast Filter */
+#define   NFP_NET_CFG_CTRL_FREELIST_EN	  (0x1 << 6) /* Freelist enable flag bit */
 
 #define NFP_NET_CFG_CAP_WORD1		0x00a4