Re: [PATCH net 1/6] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled

On Thu,  1 Oct 2026 15:24:34 -0700 Tony Nguyen wrote:

When CONFIG_NET_RX_BUSY_POLL is deactivated, fetching RX HW timestamps
from the NIC no longer works as expected, often resulting in incorrect
or negative values such as "HW raw -121948.050407424".

This occurs because disabling CONFIG_NET_RX_BUSY_POLL disables the
SKB NAPI mapping in __skb_mark_napi_id(). Consequently, get_timestamp()
fails to perform its driver lookup, and the igc driver's struct
net_device_ops::ndo_get_tstamp is never invoked.

Instead, get_timestamp() falls back to use shhwtstamps(skb)->hwtstamp,
a field that the driver has not populated. This results in incorrect
timestamps.

Fix this by populating the hwtstamp field with the correct timestamp
in the default timer when CONFIG_NET_RX_BUSY_POLL is disabled.
The "igc_adapter" is passed to igc_construct_skb() to enable
igc_ptp_rx_pktstamp() to access the necessary adapter details for
adjusting the timestamp.

looks like a driver workaround for a generic problem
a better fix is likely needed here