linux-kernel - RE: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve Tx timestamp directly from interrupt for i210

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Message-ID: <IA3PR11MB898652699383BA265C5747A5E599A@IA3PR11MB8986.namprd11.prod.outlook.com>
Date: Thu, 5 Feb 2026 09:47:14 +0000
From: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
To: Kurt Kanzenbach <kurt@...utronix.de>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>
CC: Paul Menzel <pmenzel@...gen.mpg.de>, Vadim Fedorenko
	<vadim.fedorenko@...ux.dev>, "Gomes, Vinicius" <vinicius.gomes@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Richard Cochran
	<richardcochran@...il.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Andrew Lunn <andrew+netdev@...n.ch>, "Eric
 Dumazet" <edumazet@...gle.com>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>, "Keller, Jacob E"
	<jacob.e.keller@...el.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>, "Sebastian
 Andrzej Siewior" <bigeasy@...utronix.de>
Subject: RE: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve Tx timestamp
 directly from interrupt for i210



> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf
> Of Kurt Kanzenbach
> Sent: Thursday, February 5, 2026 8:55 AM
> To: Nguyen, Anthony L <anthony.l.nguyen@...el.com>; Kitszel,
> Przemyslaw <przemyslaw.kitszel@...el.com>
> Cc: Paul Menzel <pmenzel@...gen.mpg.de>; Vadim Fedorenko
> <vadim.fedorenko@...ux.dev>; Gomes, Vinicius
> <vinicius.gomes@...el.com>; netdev@...r.kernel.org; Richard Cochran
> <richardcochran@...il.com>; Kurt Kanzenbach <kurt@...utronix.de>;
> linux-kernel@...r.kernel.org; Andrew Lunn <andrew+netdev@...n.ch>;
> Eric Dumazet <edumazet@...gle.com>; intel-wired-lan@...ts.osuosl.org;
> Keller, Jacob E <jacob.e.keller@...el.com>; Jakub Kicinski
> <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; David S. Miller
> <davem@...emloft.net>; Sebastian Andrzej Siewior
> <bigeasy@...utronix.de>
> Subject: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve Tx
> timestamp directly from interrupt for i210
> 
> Retrieve Tx timestamp directly from interrupt handler for i210.
> 
> The current implementation uses schedule_work() which is executed by
> the system work queue to retrieve Tx timestamps. This increases
> latency and can lead to timeouts in case of heavy system load. i210 is
> often used in industrial systems, where timestamp timeouts can be
> fatal.
> 
> Therefore, fetch the timestamp directly from the interrupt handler.
> 
> The work queue code stays for all other NICs supported by igb.
> 
> Tested on Intel i210 and i350.
> 
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> ---
> Changes in v3:
> - Switch back to IRQ, but for i210 only
> - Keep kworker for all other NICs like i350 (Miroslav)
> - Link to v2: https://lore.kernel.org/r/20250822-igb_irq_ts-v2-1-
> 1ac37078a7a4@...utronix.de
> 
> Changes in v2:
> - Switch from IRQ to PTP aux worker due to NTP performance regression
> (Miroslav)
> - Link to v1: https://lore.kernel.org/r/20250815-igb_irq_ts-v1-1-
> 8c6fc0353422@...utronix.de
> ---
>  drivers/net/ethernet/intel/igb/igb.h      |  1 +
>  drivers/net/ethernet/intel/igb/igb_main.c |  5 ++++-
> drivers/net/ethernet/intel/igb/igb_ptp.c  | 22 ++++++++++++++++++++++
>  3 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb.h
> b/drivers/net/ethernet/intel/igb/igb.h
> index 0fff1df81b7b..1de29670784e 100644
> --- a/drivers/net/ethernet/intel/igb/igb.h
> +++ b/drivers/net/ethernet/intel/igb/igb.h
> @@ -776,6 +776,7 @@ int igb_ptp_hwtstamp_get(struct net_device
> *netdev,  int igb_ptp_hwtstamp_set(struct net_device *netdev,
>  			 struct kernel_hwtstamp_config *config,
>  			 struct netlink_ext_ack *extack);
> +void igb_ptp_tx_tstamp_event(struct igb_adapter *adapter);
>  void igb_set_flag_queue_pairs(struct igb_adapter *, const u32);
> unsigned int igb_get_max_rss_queues(struct igb_adapter *);  #ifdef
> CONFIG_IGB_HWMON diff --git
> a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index dbea37269d2c..d0d9245e6d72 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -7078,7 +7078,10 @@ static void igb_tsync_interrupt(struct
> igb_adapter *adapter)
> 
>  	if (tsicr & E1000_TSICR_TXTS) {
>  		/* retrieve hardware timestamp */
> -		schedule_work(&adapter->ptp_tx_work);
> +		if (hw->mac.type == e1000_i210)
> +			igb_ptp_tx_tstamp_event(adapter); <-Called from IRQ!

> +		else
> +			schedule_work(&adapter->ptp_tx_work);
>  	}
> 
>  	if (tsicr & TSINTR_TT0)
> diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c
> b/drivers/net/ethernet/intel/igb/igb_ptp.c
> index bd85d02ecadd..8c8f2b8615f7 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ptp.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
> @@ -796,6 +796,28 @@ static int igb_ptp_verify_pin(struct
> ptp_clock_info *ptp, unsigned int pin,
>  	return 0;
>  }
> 
> +/**
> + * igb_ptp_tx_tstamp_event
> + * @adapter: pointer to igb adapter
> + *
> + * This function checks the TSYNCTXCTL valid bit and stores the Tx
> +hardware
> + * timestamp at the current skb.
> + **/
> +void igb_ptp_tx_tstamp_event(struct igb_adapter *adapter) {
> +	struct e1000_hw *hw = &adapter->hw;
> +	u32 tsynctxctl;
> +
> +	if (!adapter->ptp_tx_skb)
> +		return;
> +
> +	tsynctxctl = rd32(E1000_TSYNCTXCTL);
> +	if (WARN_ON_ONCE(!(tsynctxctl & E1000_TSYNCTXCTL_VALID)))
> +		return;
> +
> +	igb_ptp_tx_hwtstamp(adapter); <-Calls existing function designed for work queue!

skb_tstamp_tx() can sleep
Smells like sleep-in-atomic isn't it?

> +}
> +
>  /**
>   * igb_ptp_tx_work
>   * @work: pointer to work struct
> 
> ---
> base-commit: e07d0d30939990da377672ef49ca09763b4fbc79
> change-id: 20250813-igb_irq_ts-1aa77cc7b4cb
> 
> Best regards,
> --
> Kurt Kanzenbach <kurt@...utronix.de>