From: Jakub Kicinski <kuba@kernel.org>
To: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: davem@davemloft.net, pabeni@redhat.com, edumazet@kernel.org,
andrew+netdev@lunn.ch, netdev@vger.kernel.org,
Ding Meng <meng.ding@siemens.com>,
florian.bezdeka@siemens.com, p@1g4.org, tkusters@aweta.nl,
jiayuan.chen@linux.dev, pulehui@huawei.com,
vinicius.gomes@intel.com, maciej.fijalkowski@intel.com,
magnus.karlsson@intel.com, ast@kernel.org, daniel@iogearbox.net,
hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me,
bpf@vger.kernel.org, richardcochran@gmail.com,
dima.ruinskiy@intel.com, stable@vger.kernel.org,
Aleksandr Loktionov <aleksandr.loktionov@intel.com>,
Piotr Kwapulinski <piotr.kwapulinski@intel.com>
Subject: Re: [PATCH net 1/6] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled
Date: Wed, 7 Oct 2026 18:57:27 -0700 [thread overview]
Message-ID: <20261007185727.68180ce3@kernel.org> (raw)
In-Reply-To: <20261001222443.3500206-2-anthony.l.nguyen@intel.com>
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
prev parent reply other threads:[~2026-10-08 1:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20261001222443.3500206-1-anthony.l.nguyen@intel.com>
2026-10-01 22:24 ` [PATCH net 1/6] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled Tony Nguyen
2026-10-08 1:57 ` Jakub Kicinski [this message]
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