Re: [Intel-wired-lan] [PATCH net] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled

[Bezdeka, Florian]

On Mon, 2026-06-22 at 15:26 +0000, Loktionov, Aleksandr wrote:
> > -----Original Message-----
> > From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf
> > Of Ding Meng via Intel-wired-lan
> > Sent: Monday, June 22, 2026 6:13 AM
> > To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel,
> > Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>; andrew+netdev@xxxxxxx;
> > davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> > pabeni@xxxxxxxxxx; Kiszka, Jan <jan.kiszka@xxxxxxxxxxx>; Bezdeka,
> > Florian <florian.bezdeka@xxxxxxxxxxx>
> > Cc: intel-wired-lan@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > netdev@xxxxxxxxxxxxxxx; meng.ding@xxxxxxxxxxx; wq.wang@xxxxxxxxxxx
> > Subject: [Intel-wired-lan] [PATCH net] igc: Fix RX HW timestamp
> > reporting when NET_RX_BUSY_POLL is disabled
> > 
> > When CONFIG_NET_RX_BUSY_POLL is deactivated, fetching RX HW timestamps
> > from the NIC no longer works as expected.
> > 
> > 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.
> > 
> > Fix this by populating the hwtstamp field with the correct timestamp
> > in the default timer when CONFIG_NET_RX_BUSY_POLL is disabled.
> > 
> > Fixes: 069b142f5819 ("igc: Add support for PTP .getcyclesx64()")
> I think, because it's a fix, it needs Cc: stable@xxxxxxxxxxxxxxx

Once we hit mainline the stable machinery will pick it up by following
the Fixes: tag. If that fails for some reason we can ping stable
manually.

Florian

> 
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>
> 
> > Co-developed-by: Florian Bezdeka <florian.bezdeka@xxxxxxxxxxx>
> > Signed-off-by: Florian Bezdeka <florian.bezdeka@xxxxxxxxxxx>
> > Signed-off-by: Ding Meng <meng.ding@xxxxxxxxxxx>
> > ---
> > 

[snip]