lan7801 looses VLAN Filter Table

lan7801 looses VLAN Filter Table

[Sven Schuchmann]

Hi,
I have a problem with a lan7801 chip in Kernel 6.18. I configure VLAN-ID (2) and an IP address.
But if I disconnect and connect the network-cable several times at some point no packets are 
received anymore. Without using VLAN this does not happen.

I tracked this down that sometimes the VLAN Filter table seems
to get cleared. I hooked into the lan78xx.c driver to dump the vlan table:

static void lan78xx_get_stats(struct net_device *netdev,
			      struct ethtool_stats *stats, u64 *data)
{
	struct lan78xx_net *dev = netdev_priv(netdev);
	struct lan78xx_priv *pdata = (struct lan78xx_priv *)(dev->data[0]);

	lan78xx_update_stats(dev);

	for (int i = 0; i < 3; i++) {
		u32 buf;
		lan78xx_dataport_read(dev, DP_SEL_RSEL_VLAN_DA_, i, 1, &buf);
		if (pdata->vlan_table[i] != buf) 
			netdev_err(dev->net, "VLAN TABLE %d: 0x%08x 0x%08x", i, pdata->vlan_table[i], buf);
		else
			netdev_info(dev->net, "VLAN TABLE %d: 0x%08x 0x%08x", i, pdata->vlan_table[i], buf);
	}

So I can "read out" the table if I do "ethtool -S" and see it in the kernel log.
Normally the output looks like this:
VLAN TABLE 0: 0x00000005 0x00000005
So the table looks as expected. The Local Filter table from pdata is the same as in the chip itself.

But after some cable disconnects and connects I see this:
VLAN TABLE 0: 0x00000005 0x00000000
So the table got cleared or deleted and no paketes on VLAN-ID 2 go through.
I even can do this after I read out the table in lan78xx_get_stats():

	lan78xx_dataport_write(dev, DP_SEL_RSEL_VLAN_DA_, 0,
				DP_SEL_VHF_VLAN_LEN, pdata->vlan_table);

...and with this I can "fix" the table again from the ethtool and it starts working again.

Has someone seen something like this or can point me to a direction where
I could reinit this table (I already tried at the end of lan78xx_mac_link_up() without success...)

Thanks!

Regards, Sven

Re: lan7801 looses VLAN Filter Table

[Nicolai Buchwitz]

Hi Sven

On 18.6.2026 17:18, Sven Schuchmann wrote:
> Hi,
> I have a problem with a lan7801 chip in Kernel 6.18. I configure 
> VLAN-ID (2) and an IP address.
> But if I disconnect and connect the network-cable several times at some 
> point no packets are
> received anymore. Without using VLAN this does not happen.
> 
> I tracked this down that sometimes the VLAN Filter table seems
> to get cleared. I hooked into the lan78xx.c driver to dump the vlan 
> table:
> 
> static void lan78xx_get_stats(struct net_device *netdev,
> 			      struct ethtool_stats *stats, u64 *data)
> {
> 	struct lan78xx_net *dev = netdev_priv(netdev);
> 	struct lan78xx_priv *pdata = (struct lan78xx_priv *)(dev->data[0]);
> 
> 	lan78xx_update_stats(dev);
> 
> 	for (int i = 0; i < 3; i++) {
> 		u32 buf;
> 		lan78xx_dataport_read(dev, DP_SEL_RSEL_VLAN_DA_, i, 1, &buf);
> 		if (pdata->vlan_table[i] != buf)
> 			netdev_err(dev->net, "VLAN TABLE %d: 0x%08x 0x%08x", i, 
> pdata->vlan_table[i], buf);
> 		else
> 			netdev_info(dev->net, "VLAN TABLE %d: 0x%08x 0x%08x", i, 
> pdata->vlan_table[i], buf);
> 	}
> 
> So I can "read out" the table if I do "ethtool -S" and see it in the 
> kernel log.
> Normally the output looks like this:
> VLAN TABLE 0: 0x00000005 0x00000005
> So the table looks as expected. The Local Filter table from pdata is 
> the same as in the chip itself.
> 
> But after some cable disconnects and connects I see this:
> VLAN TABLE 0: 0x00000005 0x00000000
> So the table got cleared or deleted and no paketes on VLAN-ID 2 go 
> through.
> I even can do this after I read out the table in lan78xx_get_stats():
> 
> 	lan78xx_dataport_write(dev, DP_SEL_RSEL_VLAN_DA_, 0,
> 				DP_SEL_VHF_VLAN_LEN, pdata->vlan_table);
> 
> ...and with this I can "fix" the table again from the ethtool and it 
> starts working again.
> 
> Has someone seen something like this or can point me to a direction 
> where
> I could reinit this table (I already tried at the end of 
> lan78xx_mac_link_up() without success...)

I was able to reproduce your issue on my hardware. AFAIU the vlan table 
is not restored after USB suspend.
I will send a patch shortly. Would be great if you can test it too.

> 
> Thanks!
> 
> Regards, Sven

Thanks
Nicolai