Hi Paul, On Fri Aug 15 2025, Paul Menzel wrote: > Dear Kurt, > > > Thank you for your patch. > > Am 15.08.25 um 08:50 schrieb Kurt Kanzenbach: >> Retrieve Tx timestamp directly from interrupt handler. >> >> 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. >> >> Therefore, fetch the timestamp directly from the interrupt handler. >> >> The work queue code stays for the Intel 82576. Tested on Intel i210. > > Excuse my ignorance, I do not understand the first sentence in the last > line. Is it because the driver support different models? Why not change > it for Intel 82576 too?
Yes, the driver supports lots of different NIC(s). AFAICS Intel 82576 is the only one which does not use time sync interrupts. Probably it does not have this feature. Therefore, the 82576 needs to schedule a work queue item. > > Do you have a reproducer for the issue, so others can test. Yeah, I do have a reproducer: - Run ptp4l with 40ms tx timeout (--tx_timestamp_timeout) - Run periodic RT tasks (e.g. with SCHED_FIFO 1) with run time of 50-100ms per CPU core This leads to sporadic error messages from ptp4l such as "increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it" However, increasing the kworker priority is not an option, simply because this kworker is doing non-related PTP work items as well. As the time sync interrupt already signals that the Tx timestamp is available, there's no need to schedule a work item in this case. I might have missed something though. But my testing looked good. The warn_on never triggered. > >> Signed-off-by: Kurt Kanzenbach <[email protected]> >> --- >> drivers/net/ethernet/intel/igb/igb.h | 1 + >> drivers/net/ethernet/intel/igb/igb_main.c | 2 +- >> drivers/net/ethernet/intel/igb/igb_ptp.c | 22 ++++++++++++++++++++++ >> 3 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/net/ethernet/intel/igb/igb.h >> b/drivers/net/ethernet/intel/igb/igb.h >> index >> c3f4f7cd264e9b2ff70f03b580f95b15b528028c..102ca32e8979fa3203fc2ea36eac456f1943cfca >> 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 >> a9a7a94ae61e93aa737b0103e00580e73601d62b..8ab6e52cb839bbb698007a74462798faaaab0071 >> 100644 >> --- a/drivers/net/ethernet/intel/igb/igb_main.c >> +++ b/drivers/net/ethernet/intel/igb/igb_main.c >> @@ -7080,7 +7080,7 @@ static void igb_tsync_interrupt(struct igb_adapter >> *adapter) >> >> if (tsicr & E1000_TSICR_TXTS) { >> /* retrieve hardware timestamp */ >> - schedule_work(&adapter->ptp_tx_work); >> + igb_ptp_tx_tstamp_event(adapter); >> } >> >> 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 >> a7876882aeaf2b2a7fb9ec6ff5c83d8a1b06008a..20ecafecc60557353f8cc5ab505030246687c8e4 >> 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); >> +} >> + >> /** >> * igb_ptp_tx_work >> * @work: pointer to work struct > > The diff looks fine. > > Reviewed-by: Paul Menzel <[email protected]> Thanks!
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