Re: [Intel-wired-lan] [PATCH iwl-next v2 1/1] e1000e: correct TIMINCA on ADP/TGP systems with wrong XTAL frequency

["Lifshits, Vitaly" <vitaly.lifshits@intel.com>]

On 1/7/2026 4:19 PM, Kwapulinski, Piotr wrote:
>> -----Original Message-----
>> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of Vitaly Lifshits
>> Sent: Tuesday, January 6, 2026 11:04 AM
>> To: intel-wired-lan@lists.osuosl.org
>> Cc: Lifshits, Vitaly <vitaly.lifshits@intel.com>
>> Subject: [Intel-wired-lan] [PATCH iwl-next v2 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 interpreted as 24 MHz instead of the actual
>> 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 <vitaly.lifshits@intel.com>
>> ---
>> v2: avoid resetting the systim and rephrase commit message
>> v1: initial version
>> ---
>> drivers/net/ethernet/intel/e1000e/netdev.c | 80 ++++++++++++++++++++++
>> 1 file changed, 80 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
>> index 116f3c92b5bc..edb72054d0d9 100644
>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>> @@ -3904,6 +3904,83 @@ 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_ns;
>> +	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_ns = phc_delta - sys_delta;
>> +	if (delta_ns > 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()));
>> +		spin_unlock_irqrestore(&adapter->systim_lock, flags);
>> +
>> +		/* restore the previous hwtstamp configuration settings */
>> +		ret_val = e1000e_config_hwtstamp(adapter,
>> +						 &adapter->hwtstamp_config,
>> +						 &extack);
>> +		if (ret_val) {
>> +			if (extack._msg)
>> +				e_err("%s\n", extack._msg);
>> +		}
> Please use "if (cond1 && cond2)" instead.
> Piotr

As I mentioned previously when answering to Paul, this code was taken 
from the function e1000e_systim_reset that calls the new one I 
introduced in this patch. This is why I prefer keeping the code as is 
for consistency.