[PATCH 0/4] lan78xx minor fixes

[PATCH 0/4] lan78xx minor fixes

[Dave Stevenson]

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.

Dave Stevenson (4):
  net: lan78xx: Allow for VLAN headers in timeout calcs
  net: lan78xx: Add support for VLAN filtering.
  net: lan78xx: Add support for VLAN tag stripping.
  net: lan78xx: Use s/w csum check on VLANs without tag stripping

 drivers/net/usb/lan78xx.c | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

-- 
2.7.4

[PATCH 1/4] net: lan78xx: Allow for VLAN headers in timeout calcs

[Dave Stevenson]

The frame abort timeout being set by lan78xx_set_rx_max_frame_length
didn't account for any VLAN headers, resulting in very low
throughput if used with tagged VLANs.

Use VLAN_ETH_HLEN instead of ETH_HLEN to correct for this.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
---
 drivers/net/usb/lan78xx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index a89570f..2f793d4 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2298,7 +2298,7 @@ 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;
 
@@ -2587,7 +2587,8 @@ 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_;
-- 
2.7.4

[PATCH 2/4] net: lan78xx: Add support for VLAN filtering.

[Dave Stevenson]

HW_VLAN_CTAG_FILTER was partially implemented, but not advertised
to Linux.

Complete the implementation of this.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
---
 drivers/net/usb/lan78xx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 2f793d4..afe7fa3 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2363,7 +2363,7 @@ static int lan78xx_set_features(struct net_device *netdev,
 		pdata->rfe_ctl &= ~(RFE_CTL_ICMP_COE_ | RFE_CTL_IGMP_COE_);
 	}
 
-	if (features & NETIF_F_HW_VLAN_CTAG_RX)
+	if (features & NETIF_F_HW_VLAN_CTAG_FILTER)
 		pdata->rfe_ctl |= RFE_CTL_VLAN_FILTER_;
 	else
 		pdata->rfe_ctl &= ~RFE_CTL_VLAN_FILTER_;
@@ -2976,6 +2976,9 @@ 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_FILTER_ENABLE)
+		dev->net->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
+
 	dev->net->hw_features = dev->net->features;
 
 	ret = lan78xx_setup_irq_domain(dev);
-- 
2.7.4

[PATCH 3/4] net: lan78xx: Add support for VLAN tag stripping.

[Dave Stevenson]

The chip supports stripping the VLAN tag and reporting it
in metadata.
Complete the support for this.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
---
 drivers/net/usb/lan78xx.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index afe7fa3..f72a8f5 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/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
 
@@ -2363,6 +2364,11 @@ static int lan78xx_set_features(struct net_device *netdev,
 		pdata->rfe_ctl &= ~(RFE_CTL_ICMP_COE_ | RFE_CTL_IGMP_COE_);
 	}
 
+	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
@@ -2976,6 +2982,9 @@ 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;
 
@@ -3052,6 +3061,16 @@ 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;
@@ -3116,6 +3135,8 @@ 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);
@@ -3134,6 +3155,7 @@ 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);
-- 
2.7.4

[PATCH 4/4] net: lan78xx: Use s/w csum check on VLANs without tag stripping

[Dave Stevenson]

Observations of VLANs dropping packets due to invalid
checksums when not offloading VLAN tag receive.
With VLAN tag stripping enabled no issue is observed.

Drop back to s/w checksums if VLAN offload is disabled.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
---
 drivers/net/usb/lan78xx.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index f72a8f5..6f2ea84 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3052,8 +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_));
-- 
2.7.4

Re: [PATCH 0/4] lan78xx minor fixes

[David Miller]

From: Dave Stevenson <dave.stevenson@raspberrypi.org>
Date: Mon, 25 Jun 2018 15:07:11 +0100

> 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
 ...

Series applied, thank you.