[PATCH net-next 0/3] Improve phc2sys precision for mv88e6xxx switch in combination with imx6-fec

[Hubert Feurstein]

With this patchset the phc2sys synchronisation precision improved to +/-555ns on an IMX6DL with an MV88E6220 switch attached.

This patchset takes into account the comments from the following discussions:
- https://lkml.org/lkml/2019/8/2/1364
- https://lkml.org/lkml/2019/8/5/169

Patch 01 adds the required infrastructure in the MDIO layer.
Patch 02 adds support for the PTP_SYS_OFFSET_EXTENDED ioctl in the mv88e6xxx driver.
Patch 03 adds support for the PTP system timestamping in the imx-fec driver.

The following tests show the improvement caused by each patch. The system clock precision was set to 15ns instead of 333ns (as described in https://lkml.org/lkml/2019/8/2/1364).

Without this patchset applied, the phc2sys synchronisation performance was very poor:

  offset: min -27120 max 28840 mean 2.44 stddev 8040.78 count 1236
  delay:  min 282103 max 386385 mean 352568.03 stddev 27814.27 count 1236
  (test runtime 20 minutes)

Results after appling patch 01 and 02:

  offset: min -12316 max 13314 mean -9.38 stddev 4274.82 count 1022
  delay:  min 69977 max 96266 mean 87939.04 stddev 6466.17 count 1022
  (test runtime 16 minutes)

Results after appling patch 03:

  offset: min -788 max 528 mean -0.06 stddev 185.02 count 7171
  delay:  min 1773 max 2031 mean 1909.43 stddev 33.74 count 7171
  (test runtime 119 minutes)

Hubert Feurstein (3):
  net: mdio: add support for passing a PTP system timestamp to the
    mii_bus driver
  net: dsa: mv88e6xxx: extend PTP gettime function to read system clock
  net: fec: add support for PTP system timestamping for MDIO devices

 drivers/net/dsa/mv88e6xxx/chip.h          |   2 +
 drivers/net/dsa/mv88e6xxx/ptp.c           |  11 ++-
 drivers/net/dsa/mv88e6xxx/smi.c           |   3 +-
 drivers/net/ethernet/freescale/fec_main.c |   3 +
 drivers/net/phy/mdio_bus.c                | 105 ++++++++++++++++++++++
 include/linux/mdio.h                      |   7 ++
 include/linux/phy.h                       |  25 ++++++
 7 files changed, 151 insertions(+), 5 deletions(-)

-- 
2.22.1