Merge branch 'lan78xx-minor-fixes'

Dave Stevenson says:

====================
lan78xx minor fixes

This is a small set of patches for the Microchip LAN78xx chip,
as used in the Raspberry Pi 3B+.
The main debug/discussion was on
https://github.com/raspberrypi/linux/issues/2458

Initial symptoms were that VLANs were very unreliable.
A couple of things were found:
- firstly that the hardware timeout value set failed to
  take into account the VLAN tag, so a full MTU packet
  would be timed out.
- second was that regular checksum failures were being
  reported. Disabling checksum offload confirmed that
  the checksums were valid, and further experimentation
  identified that it was only if the VLAN tags were being
  passed through to the kernel that there were issues.
  The hardware supports VLAN filtering and tag stripping,
  therefore those have been implemented (much of the work
  was already done), and the driver drops back to s/w
  checksums should the choice be made not to use the h/w
  VLAN stripping.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/lan78xx.c

@@ -64,6 +64,7 @@
 #define DEFAULT_RX_CSUM_ENABLE		(true)
 #define DEFAULT_TSO_CSUM_ENABLE		(true)
 #define DEFAULT_VLAN_FILTER_ENABLE	(true)
+#define DEFAULT_VLAN_RX_OFFLOAD		(true)
 #define TX_OVERHEAD			(8)
 #define RXW_PADDING			2
 
@@ -2298,7 +2299,7 @@ static int lan78xx_change_mtu(struct net_device *netdev, int new_mtu)
 	if ((ll_mtu % dev->maxpacket) == 0)
 		return -EDOM;
 
-	ret = lan78xx_set_rx_max_frame_length(dev, new_mtu + ETH_HLEN);
+	ret = lan78xx_set_rx_max_frame_length(dev, new_mtu + VLAN_ETH_HLEN);
 
 	netdev->mtu = new_mtu;
 
@@ -2364,6 +2365,11 @@ static int lan78xx_set_features(struct net_device *netdev,
 	}
 
 	if (features & NETIF_F_HW_VLAN_CTAG_RX)
+		pdata->rfe_ctl |= RFE_CTL_VLAN_STRIP_;
+	else
+		pdata->rfe_ctl &= ~RFE_CTL_VLAN_STRIP_;
+
+	if (features & NETIF_F_HW_VLAN_CTAG_FILTER)
 		pdata->rfe_ctl |= RFE_CTL_VLAN_FILTER_;
 	else
 		pdata->rfe_ctl &= ~RFE_CTL_VLAN_FILTER_;
@@ -2587,7 +2593,8 @@ static int lan78xx_reset(struct lan78xx_net *dev)
 	buf |= FCT_TX_CTL_EN_;
 	ret = lan78xx_write_reg(dev, FCT_TX_CTL, buf);
 
-	ret = lan78xx_set_rx_max_frame_length(dev, dev->net->mtu + ETH_HLEN);
+	ret = lan78xx_set_rx_max_frame_length(dev,
+					      dev->net->mtu + VLAN_ETH_HLEN);
 
 	ret = lan78xx_read_reg(dev, MAC_RX, &buf);
 	buf |= MAC_RX_RXEN_;
@@ -2975,6 +2982,12 @@ static int lan78xx_bind(struct lan78xx_net *dev, struct usb_interface *intf)
 	if (DEFAULT_TSO_CSUM_ENABLE)
 		dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_SG;
 
+	if (DEFAULT_VLAN_RX_OFFLOAD)
+		dev->net->features |= NETIF_F_HW_VLAN_CTAG_RX;
+
+	if (DEFAULT_VLAN_FILTER_ENABLE)
+		dev->net->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
+
 	dev->net->hw_features = dev->net->features;
 
 	ret = lan78xx_setup_irq_domain(dev);
@@ -3039,8 +3052,13 @@ static void lan78xx_rx_csum_offload(struct lan78xx_net *dev,
 				    struct sk_buff *skb,
 				    u32 rx_cmd_a, u32 rx_cmd_b)
 {
+	/* HW Checksum offload appears to be flawed if used when not stripping
+	 * VLAN headers. Drop back to S/W checksums under these conditions.
+	 */
 	if (!(dev->net->features & NETIF_F_RXCSUM) ||
-	    unlikely(rx_cmd_a & RX_CMD_A_ICSM_)) {
+	    unlikely(rx_cmd_a & RX_CMD_A_ICSM_) ||
+	    ((rx_cmd_a & RX_CMD_A_FVTG_) &&
+	     !(dev->net->features & NETIF_F_HW_VLAN_CTAG_RX))) {
 		skb->ip_summed = CHECKSUM_NONE;
 	} else {
 		skb->csum = ntohs((u16)(rx_cmd_b >> RX_CMD_B_CSUM_SHIFT_));
@@ -3048,6 +3066,16 @@ static void lan78xx_rx_csum_offload(struct lan78xx_net *dev,
 	}
 }
 
+static void lan78xx_rx_vlan_offload(struct lan78xx_net *dev,
+				    struct sk_buff *skb,
+				    u32 rx_cmd_a, u32 rx_cmd_b)
+{
+	if ((dev->net->features & NETIF_F_HW_VLAN_CTAG_RX) &&
+	    (rx_cmd_a & RX_CMD_A_FVTG_))
+		__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q),
+				       (rx_cmd_b & 0xffff));
+}
+
 static void lan78xx_skb_return(struct lan78xx_net *dev, struct sk_buff *skb)
 {
 	int		status;
@@ -3112,6 +3140,8 @@ static int lan78xx_rx(struct lan78xx_net *dev, struct sk_buff *skb)
 			if (skb->len == size) {
 				lan78xx_rx_csum_offload(dev, skb,
 							rx_cmd_a, rx_cmd_b);
+				lan78xx_rx_vlan_offload(dev, skb,
+							rx_cmd_a, rx_cmd_b);
 
 				skb_trim(skb, skb->len - 4); /* remove fcs */
 				skb->truesize = size + sizeof(struct sk_buff);
@@ -3130,6 +3160,7 @@ static int lan78xx_rx(struct lan78xx_net *dev, struct sk_buff *skb)
 			skb_set_tail_pointer(skb2, size);
 
 			lan78xx_rx_csum_offload(dev, skb2, rx_cmd_a, rx_cmd_b);
+			lan78xx_rx_vlan_offload(dev, skb2, rx_cmd_a, rx_cmd_b);
 
 			skb_trim(skb2, skb2->len - 4); /* remove fcs */
 			skb2->truesize = size + sizeof(struct sk_buff);