[PATCH net-next v4 7/8] net: bcmgenet: allow the MTU to be changed

@@ -84,6 +84,12 @@
 				      ENET_THLD_MAX * ENET_THLD_UNIT, \
 				      ENET_THLD_PAGE_LEN)
 
+/* Largest MTU that fits one descriptor, with room for a VLAN tag so a VLAN
+ * interface can use the parent MTU.
+ */
+#define ENET_MAX_MTU		(ENET_THLD_MAX_LEN - GENET_RBUF_ALIGN - \
+				 ETH_HLEN - VLAN_HLEN)
+
 /* Tx/Rx DMA register offset, skip 256 descriptors */
 #define WORDS_PER_BD(p)		(p->hw_params->words_per_bd)
 #define DMA_DESC_SIZE		(WORDS_PER_BD(priv) * sizeof(u32))

@@ -3179,8 +3185,12 @@ static int bcmgenet_init_rx_queues(struct net_device *dev)
 	/* Initialize Rx priority queues */
 	for (i = 0; i <= priv->hw_params->rx_queues; i++) {
 		ret = bcmgenet_init_rx_ring(priv, i, end - start, start, end);
-		if (ret)
+		if (ret) {
+			/* Only the rings before this one hold a NAPI */
+			while (i--)
+				netif_napi_del(&priv->rx_rings[i].napi);
 			return ret;
+		}
 
 		start = end;
 		end += priv->hw_params->rx_bds_per_q;

@@ -3564,6 +3574,7 @@ static int bcmgenet_open(struct net_device *dev)
 
 	bcmgenet_netif_start(dev, true);
 
+	priv->datapath_up = true;
 	netif_tx_start_all_queues(dev);
 
 	return 0;

@@ -3622,7 +3633,11 @@ static int bcmgenet_close(struct net_device *dev)
 
 	netif_dbg(priv, ifdown, dev, "bcmgenet_close\n");
 
-	bcmgenet_netif_stop(dev, false);
+	/* A failed MTU change can have torn the datapath down already */
+	if (priv->datapath_up) {
+		bcmgenet_netif_stop(dev, false);
+		priv->datapath_up = false;
+	}
 
 	/* Really kill the PHY state machine and disconnect from it */
 	phy_disconnect(dev->phydev);

@@ -3870,6 +3885,76 @@ static int bcmgenet_change_carrier(struct net_device *dev, bool new_carrier)
 	return 0;
 }
 
+static int bcmgenet_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct bcmgenet_priv *priv = netdev_priv(dev);
+	unsigned int old_mtu = dev->mtu;
+	int ret;
+
+	/* Every MTU dependent value is floored at ETH_DATA_LEN, so a change
+	 * below it reprograms nothing and must not cost queued frames.
+	 */
+	if (!netif_running(dev) ||
+	    max_t(unsigned int, old_mtu, ETH_DATA_LEN) ==
+	    max_t(unsigned int, new_mtu, ETH_DATA_LEN)) {
+		WRITE_ONCE(dev->mtu, new_mtu);
+		priv->rx_buf_len = bcmgenet_rx_buf_len(new_mtu);
+		return 0;
+	}
+
+	/* The watchdog trips on an idle queue once the rings are gone */
+	netif_device_detach(dev);
+
+	/* Only the buffers and the MTU registers change, leave the PHY up */
+	bcmgenet_netif_stop(dev, false);
+	priv->datapath_up = false;
+
+	WRITE_ONCE(dev->mtu, new_mtu);
+	priv->rx_buf_len = bcmgenet_rx_buf_len(new_mtu);
+	bcmgenet_set_mtu_regs(priv, new_mtu);
+
+	ret = bcmgenet_init_dma(priv, true);
+	if (ret) {
+		/* Retry the size that was allocated a moment ago */
+		WRITE_ONCE(dev->mtu, old_mtu);
+		priv->rx_buf_len = bcmgenet_rx_buf_len(old_mtu);
+		bcmgenet_set_mtu_regs(priv, old_mtu);
+		if (bcmgenet_init_dma(priv, true)) {
+			/* Nothing left to run on. Take the interface down so
+			 * that close and suspend do not tear it down twice.
+			 */
+			netdev_err(dev, "failed to restore MTU %u, closing\n",
+				   old_mtu);
+			netif_close(dev);
+
+			/* Mark the device present again, __dev_open()
+			 * refuses a detached one. The queues stay stopped
+			 * because the interface is down by now.
+			 */
+			netif_device_attach(dev);
+			return ret;
+		}
+	}
+
+	bcmgenet_hfb_restore(priv);
+	bcmgenet_netif_start(dev, false);
+
+	/* bcmgenet_netif_start() only restores the link interrupt */
+	if (bcmgenet_has_mdio_intr(priv))
+		bcmgenet_intrl2_0_writel(priv, UMAC_IRQ_MDIO_EVENT,
+					 INTRL2_CPU_MASK_CLEAR);
+
+	/* A link event latched while the interrupts were off is gone. Internal
+	 * PHYs on GENET v1-v4 are not polled, so resync the state machine.
+	 */
+	phy_mac_interrupt(dev->phydev);
+
+	priv->datapath_up = true;
+	netif_device_attach(dev);
+
+	return ret;
+}
+
 static const struct net_device_ops bcmgenet_netdev_ops = {
 	.ndo_open		= bcmgenet_open,
 	.ndo_stop		= bcmgenet_close,

@@ -3881,6 +3966,7 @@ static const struct net_device_ops bcmgenet_netdev_ops = {
 	.ndo_set_features	= bcmgenet_set_features,
 	.ndo_get_stats64	= bcmgenet_get_stats64,
 	.ndo_change_carrier	= bcmgenet_change_carrier,
+	.ndo_change_mtu		= bcmgenet_change_mtu,
 };
 
 /* GENET hardware parameters/characteristics */

@@ -4234,7 +4320,11 @@ static int bcmgenet_probe(struct platform_device *pdev)
 	/* Mii wait queue */
 	init_waitqueue_head(&priv->wq);
 	bcmgenet_hfb_init(priv);
+
+	/* v1 cannot program the thresholds, so it stays at the default MTU */
 	priv->rx_buf_len = bcmgenet_rx_buf_len(dev->mtu);
+	if (!GENET_IS_V1(priv))
+		dev->max_mtu = ENET_MAX_MTU;
 	INIT_WORK(&priv->bcmgenet_irq_work, bcmgenet_irq_task);
 
 	priv->clk_wol = devm_clk_get_optional(&priv->pdev->dev, "enet-wol");

@@ -4418,6 +4508,7 @@ static int bcmgenet_resume(struct device *d)
 		bcmgenet_rdma_disable(priv);
 		bcmgenet_intr_disable(priv);
 		bcmgenet_fini_dma(priv);
+		priv->datapath_up = false;
 		enable_irq(priv->irq1);
 	}
 

@@ -4449,6 +4540,7 @@ static int bcmgenet_resume(struct device *d)
 
 	bcmgenet_netif_start(dev, true);
 
+	priv->datapath_up = true;
 	netif_device_attach(dev);
 
 	return 0;

@@ -4510,6 +4602,7 @@ static int bcmgenet_suspend(struct device *d)
 	} else {
 		/* Teardown the interface */
 		bcmgenet_netif_stop(dev, true);
+		priv->datapath_up = false;
 	}
 
 	return 0;

@@ -636,6 +636,7 @@ struct bcmgenet_priv {
 	unsigned autoneg_pause:1;
 	unsigned tx_pause:1;
 	unsigned rx_pause:1;
+	unsigned datapath_up:1;
 
 	/* MDIO bus variables */
 	wait_queue_head_t wq;