diff options
| author | Jinhui Guo <guojinhui.liam@bytedance.com> | 2026-07-30 13:13:41 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-05 18:08:50 -0700 |
| commit | 089ca284afb0f3b2870a5ce41524cbc91ed350d4 (patch) | |
| tree | 008be8e05a9a92cfdc91d721ff88bcb40dc9a49e | |
| parent | 90359b528888e1275b4fe014b31ee23bc7eaf7be (diff) | |
net: usb: cdc_ether: add quirk for AMI BMC stale link events
On AMD Genoa/Turin platforms the BMC-provided USB-Ethernet gadget
(American Megatrends, VID 0x046b PID 0xffb0) intermittently fails to
respond to ARP after AC cold boot. usbmon captures a stale
NETWORK_CONNECTION(off) immediately followed by
NETWORK_CONNECTION(on) on the interrupt endpoint (~130us apart)
after enumeration. Because alloc_netdev() leaves
__LINK_STATE_NOCARRIER cleared, netif_carrier_ok() returns true
when the spurious OFF arrives, so usbnet_cdc_status() cannot
recognise it as redundant and schedules EVENT_LINK_CHANGE.
__handle_link_change() then calls unlink_urbs(), killing ~60 rx
URBs whose payload has already been DMA'd into memory — xHCI trace
confirms them completing as -ECONNRESET with non-zero residual
length. rx_complete() drops these unconditionally. The following
ON restores the carrier and re-submits URBs, but the ARP reply is
already lost; the interface looks "up but silent" until ifdown/ifup.
Fix this by adding a device-specific quirk with FLAG_LINK_INTR set,
which makes usbnet_probe() call netif_carrier_off() after bind.
With initial carrier == OFF, usbnet_cdc_status() recognises the
spurious OFF as matching the current state and drops it; the
subsequent ON is the first real event and brings the link up
cleanly without ever tearing down the rx queue. The scheduled
link-change kevent is harmless because EVENT_DEV_OPEN is not yet
set at probe time.
This is applied as a device-specific quirk rather than a change to
the shared cdc_info driver_info because some CDC devices never
send NETWORK_CONNECTION notifications; forcing carrier off for
them would leave the link permanently DOWN. Restricting the change
to this VID/PID keeps that class of device untouched.
Tested on Genoa and Turin across 100+ AC cold boot cycles; ping
first-packet success rate went from intermittent to 100%.
Signed-off-by: Jinhui Guo <guojinhui.liam@bytedance.com>
Link: https://patch.msgid.link/20260730051341.24930-1-guojinhui.liam@bytedance.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/usb/cdc_ether.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c index a0a5740590b9..b5e4b195b69a 100644 --- a/drivers/net/usb/cdc_ether.c +++ b/drivers/net/usb/cdc_ether.c @@ -538,6 +538,16 @@ static const struct driver_info cdc_info = { .manage_power = usbnet_manage_power, }; +static const struct driver_info ami_bmc_info = { + .description = "AMI BMC USB Ethernet", + .flags = FLAG_ETHER | FLAG_POINTTOPOINT | FLAG_LINK_INTR, + .bind = usbnet_cdc_bind, + .unbind = usbnet_cdc_unbind, + .status = usbnet_cdc_status, + .set_rx_mode = usbnet_cdc_update_filter, + .manage_power = usbnet_manage_power, +}; + static const struct driver_info zte_cdc_info = { .description = "ZTE CDC Ethernet Device", .flags = FLAG_ETHER | FLAG_POINTTOPOINT, @@ -947,6 +957,12 @@ static const struct usb_device_id products[] = { USB_CDC_PROTO_NONE), .driver_info = (unsigned long)&wwan_info, }, { + /* AMI BMC gadget */ + USB_DEVICE_AND_INTERFACE_INFO(0x046b, 0xffb0, USB_CLASS_COMM, + USB_CDC_SUBCLASS_ETHERNET, + USB_CDC_PROTO_NONE), + .driver_info = (unsigned long)&ami_bmc_info, +}, { USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE), .driver_info = (unsigned long) &cdc_info, |