e1000e: don't modify SYSTIM registers during SIOCSHWTSTAMP ioctl

The e1000e_config_hwtstamp function was incorrectly resetting the SYSTIM registers every time the ioctl was being run. If you happened to be running ptp4l and lost the PTP connect (removing cable, or blocking the UDP traffic for example), then ptp4l will eventually perform a restart which involves re-requesting timestamp settings. In e1000e this has the unfortunate and incorrect result of resetting SYSTIME to the kernel time. Since kernel time is usually in UTC, and PTP time is in TAI, this results in the leap second being re-applied.

Fix this by extracting the SYSTIME reset out into its own function, e1000e_ptp_reset, which we call during reset to restore the hardware registers. This function will (a) restart the timecounter based on the new system time, (b) restore the previous PPB setting, and (c) restore the previous hwtstamp settings.

In order to perform (b), I had to modify the adjfreq ptp function pointer to store the old delta each time it is called. This also has the side effect of restoring the correct base timinca register correctly. The driver does not need to explicitly zero the ptp_delta variable since the entire adapter structure comes zero-initialized.

Reported-by Brian Walsh <[email protected]>

Signed-off-by Jacob Keller <[email protected]>

---

3rd time's a charm? This time I verified it should compile and run now, without crashes, and without compilation errors.

Notes:
This patch conflicts with Brian's "e1000e fix ptp time reset on newtork interruption", and that patch MUST be removed from the queue before applying this one.

- Changes since v1
* move e1000e_init_ptp prior to reset so that PTP clock is created first
* handle NULL ptp_clock_info gracefully.

- Changes since v2
* fix stupid compilation error
* fix stupid null pointer check (who WROTE THIS CODE?!?!??!! ;)

 drivers/net/ethernet/intel/e1000e/e1000.h  |  1 +
 drivers/net/ethernet/intel/e1000e/netdev.c | 65 ++++++++++++++++++++++--------
 drivers/net/ethernet/intel/e1000e/ptp.c    |  2 +
 3 files changed, 52 insertions(+), 16 deletions(-)

Quoted 57 lines · Jacob Keller

The e1000e_config_hwtstamp function was incorrectly resetting the SYSTIM
registers every time the ioctl was being run. If you happened to be running ptp4l and lost the PTP connect (removing cable, or blocking the
UDP traffic for example), then ptp4l will eventually perform a restart
which involves re-requesting timestamp settings. In e1000e this has the
unfortunate and incorrect result of resetting SYSTIME to the kernel time. Since kernel time is usually in UTC, and PTP time is in TAI, this
results in the leap second being re-applied.

Fix this by extracting the SYSTIME reset out into its own function, e1000e_ptp_reset, which we call during reset to restore the hardware
registers. This function will (a) restart the timecounter based on the
new system time, (b) restore the previous PPB setting, and (c) restore
the previous hwtstamp settings.

In order to perform (b), I had to modify the adjfreq ptp function pointer to store the old delta each time it is called. This also has the
side effect of restoring the correct base timinca register correctly.
The driver does not need to explicitly zero the ptp_delta variable since
the entire adapter structure comes zero-initialized.

Reported-by Brian Walsh <[email protected]>

Signed-off-by Jacob Keller <[email protected]>

---

3rd time's a charm? This time I verified it should compile and run now,
without crashes, and without compilation errors.

Notes:
????This patch conflicts with Brian's "e1000e fix ptp time reset on newtork
????interruption", and that patch MUST be removed from the queue before applying
????this one.
????
????- Changes since v1
????* move e1000e_init_ptp prior to reset so that PTP clock is created first
????* handle NULL ptp_clock_info gracefully.
????
????- Changes since v2
????* fix stupid compilation error
????* fix stupid null pointer check (who WROTE THIS CODE?!?!??!! ;)

Quoted 6 lines

?drivers/net/ethernet/intel/e1000e/e1000.h??|??1 + ?drivers/net/ethernet/intel/e1000e/netdev.c | 65
++++++++++++++++++++++--------
?drivers/net/ethernet/intel/e1000e/ptp.c????|??2 + ?3 files changed, 52 insertions(+), 16 deletions(-)

Fixes the leapsecond time jump I was trying to fix.

Tested-by Brian Walsh <[email protected]>

The e1000e_config_hwtstamp function was incorrectly resetting the SYSTIM
registers every time the ioctl was being run. If you happened to be running ptp4l and lost the PTP connect (removing cable, or blocking the
UDP traffic for example), then ptp4l will eventually perform a restart
which involves re-requesting timestamp settings. In e1000e this has the
unfortunate and incorrect result of resetting SYSTIME to the kernel time. Since kernel time is usually in UTC, and PTP time is in TAI, this
results in the leap second being re-applied.

Fix this by extracting the SYSTIME reset out into its own function, e1000e_ptp_reset, which we call during reset to restore the hardware registers. This function will (a) restart the timecounter based on the
new system time, (b) restore the previous PPB setting, and (c) restore
the previous hwtstamp settings.

In order to perform (b), I had to modify the adjfreq ptp function pointer to store the old delta each time it is called. This also has the
side effect of restoring the correct base timinca register correctly. The driver does not need to explicitly zero the ptp_delta variable since
the entire adapter structure comes zero-initialized.

Reported-by Brian Walsh <[email protected]>

Signed-off-by Jacob Keller <[email protected]>