> -----Original Message-----
> From: Intel-wired-lan <[email protected]> On Behalf
> Of Vitaly Lifshits
> Sent: Monday, January 5, 2026 8:58 AM
> To: [email protected]
> Cc: Lifshits, Vitaly <[email protected]>
> Subject: [Intel-wired-lan] [PATCH iwl-next v1 1/1] e1000e: correct
> TIMINCA on ADP/TGP systems with wrong XTAL frequency
>
> On some Tiger Lake (TGP) and Alder Lake (ADP) platforms, the hardware
> XTAL clock is incorrectly configured to 24 MHz instead of the expected
> 38.4 MHz. This causes the PHC to run significantly faster than system
> time, breaking PTP synchronization.
>
> To mitigate this at runtime, measure PHC vs system time over ~1 ms
> using cross-timestamps. If the PHC increment differs from system time
> beyond the expected tolerance (currently >100 uSecs), reprogram
> TIMINCA for the
> 38.4 MHz profile and reinitialize the timecounter.
>
> Tested on an affected system using phc_ctl:
> Without fix:
> sudo phc_ctl enp0s31f6 set 0.0 wait 10 get clock time: 16.000541250
> (expected ~10s)
>
> With fix:
> sudo phc_ctl enp0s31f6 set 0.0 wait 10 get clock time: 9.984407212
> (expected ~10s)
>
> Signed-off-by: Vitaly Lifshits <[email protected]>
> ---
> drivers/net/ethernet/intel/e1000e/netdev.c | 79
> ++++++++++++++++++++++
> 1 file changed, 79 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
> b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 116f3c92b5bc..4ab6897577e5 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -3904,6 +3904,82 @@ static void e1000_flush_desc_rings(struct
> e1000_adapter *adapter)
> e1000_flush_rx_ring(adapter);
> }
>
> +/**
> + * e1000e_xtal_tgp_workaround - Adjust XTAL clock based on PHC and
> +system
> + * clock delta.
> + *
> + * Measures the time difference between the PHC (Precision Hardware
> +Clock)
> + * and the system clock over a 1 millisecond interval. If the delta
> + * exceeds 100 microseconds, reconfigure the XTAL clock to 38.4 MHz.
> + *
> + * @adapter: Pointer to the private adapter structure **/ static
> void
> +e1000e_xtal_tgp_workaround(struct e1000_adapter *adapter) {
> + s64 phc_delta, sys_delta, sys_start_ns, sys_end_ns, delta;
> + struct ptp_system_timestamp sys_start = {}, sys_end = {};
> + struct ptp_clock_info *info = &adapter->ptp_clock_info;
> + struct timespec64 phc_start, phc_end;
> + struct e1000_hw *hw = &adapter->hw;
> + struct netlink_ext_ack extack = {};
> + unsigned long flags;
> + u32 timinca;
> + s32 ret_val;
> +
> + /* Capture start */
> + if (info->gettimex64(info, &phc_start, &sys_start)) {
> + e_dbg("PHC gettimex(start) failed\n");
> + return;
> + }
> +
> + /* Small interval to measure increment */
> + usleep_range(1000, 1100);
> +
> + /* Capture end */
> + if (info->gettimex64(info, &phc_end, &sys_end)) {
> + e_dbg("PHC gettimex(end) failed\n");
> + return;
> + }
> +
> + /* Compute deltas */
> + phc_delta = timespec64_to_ns(&phc_end) -
> + timespec64_to_ns(&phc_start);
> +
> + sys_start_ns = (timespec64_to_ns(&sys_start.pre_ts) +
> + timespec64_to_ns(&sys_start.post_ts)) >> 1;
> +
> + sys_end_ns = (timespec64_to_ns(&sys_end.pre_ts) +
> + timespec64_to_ns(&sys_end.post_ts)) >> 1;
> +
> + sys_delta = sys_end_ns - sys_start_ns;
> +
> + delta = phc_delta - sys_delta;
> + if (delta > 100000) {
> + e_dbg("Corrected PHC frequency: TIMINCA set for 38.4
> MHz\n");
> + /* Program TIMINCA for 38.4 MHz */
> + timinca = (INCPERIOD_38400KHZ <<
> + E1000_TIMINCA_INCPERIOD_SHIFT) |
> + (((INCVALUE_38400KHZ <<
> + adapter->cc.shift) &
> + E1000_TIMINCA_INCVALUE_MASK));
> + ew32(TIMINCA, timinca);
> + }
> +
> + /* reset the systim ns time counter */
> + spin_lock_irqsave(&adapter->systim_lock, flags);
> + timecounter_init(&adapter->tc, &adapter->cc,
> + ktime_to_ns(ktime_get_real()));
Unconditional timecounter reinitialization occurs even when TIMINCA is not
modified (when delta <= 100000).
Isn't it an issue?
> + spin_unlock_irqrestore(&adapter->systim_lock, flags);
> +
> + /* restore the previous hwtstamp configuration settings */
> + ret_val = e1000e_config_hwtstamp(adapter, &adapter-
> >hwtstamp_config,
> + &extack);
Unconditional e1000e_config_hwtstamp() call occurs even when no TIMINCA
correction is applied,
causing unnecessary hardware reprogramming and potential side effects on
systems with correct XTAL frequency.
Isn't it an issue too?
> + if (ret_val) {
> + if (extack._msg)
> + e_err("%s\n", extack._msg);
> + }
> +}
> +
> /**
> * e1000e_systim_reset - reset the timesync registers after a
> hardware reset
> * @adapter: board private structure
> @@ -3955,6 +4031,9 @@ static void e1000e_systim_reset(struct
> e1000_adapter *adapter)
> if (extack._msg)
> e_err("%s\n", extack._msg);
> }
> +
> + if (hw->mac.type == e1000_pch_adp || hw->mac.type ==
> e1000_pch_tgp)
> + return e1000e_xtal_tgp_workaround(adapter);
> }
>
> /**
> --
> 2.34.1
