Merge branch 'PTP-support-for-the-SJA1105-DSA-driver'

Vladimir Oltean says:

====================
PTP support for the SJA1105 DSA driver

This patchset adds the following:

 - A timecounter/cyclecounter based PHC for the free-running
   timestamping clock of this switch.

 - A state machine implemented in the DSA tagger for SJA1105, which
   keeps track of metadata follow-up Ethernet frames (the switch's way
   of transmitting RX timestamps).

Clock manipulations on the actual hardware PTP clock will have to be
implemented anyway, for the TTEthernet block and the time-based ingress
policer.

v3 patchset can be found at:
https://lkml.org/lkml/2019/6/4/954

Changes from v3:

- Made it compile with the SJA1105 DSA driver and PTP driver as modules.

- Reworked/simplified/fixed some issues in 03/17
  (dsa_8021q_remove_header) and added an ASCII image that
  illustrates the transformation that is taking place.

- Removed a useless check for sja1105_is_link_local from 16/17 (RX
  timestamping) which also made previous 08/17 patch ("Move
  sja1105_is_link_local to include/linux") useless and therefore dropped.

v2 patchset can be found at:
https://lkml.org/lkml/2019/6/2/146

Changes from v2:

- Broke previous 09/10 patch (timestamping) into multiple smaller
  patches.

- Every patch in the series compiles.

v1 patchset can be found at:
https://lkml.org/lkml/2019/5/28/1093

Changes from v1:

- Removed the addition of the DSA .can_timestamp callback.

- Waiting for meta frames is done completely inside the tagger, and all
  frames emitted on RX are already partially timestamped.

- Added a global data structure for the tagger common to all ports.

- Made PTP work with ports in standalone mode, by limiting use of the
  DMAC-mangling "incl_srcpt" mode only when ports are bridged, aka when
  the DSA master is already promiscuous and can receive anything.
  Also changed meta frames to be sent at the 01-80-C2-00-00-0E DMAC.

- Made some progress w.r.t. observed negative path delay.  Apparently it
  only appears when the delay mechanism is the delay request-response
  (end-to-end) one. If peer delay is used (-P), the path delay is
  positive and appears reasonable for an 1000Base-T link (485 ns in
  steady state).

  SJA1105 as PTP slave (OC) with E2E path delay:

ptp4l[55.600]: master offset          8 s2 freq  +83677 path delay     -2390
ptp4l[56.600]: master offset         17 s2 freq  +83688 path delay     -2391
ptp4l[57.601]: master offset          6 s2 freq  +83682 path delay     -2391
ptp4l[58.601]: master offset         -1 s2 freq  +83677 path delay     -2391

  SJA1105 as PTP slave (OC) with P2P path delay:

ptp4l[48.343]: master offset          5 s2 freq  +83715 path delay       484
ptp4l[48.468]: master offset         -3 s2 freq  +83705 path delay       485
ptp4l[48.593]: master offset          0 s2 freq  +83708 path delay       485
ptp4l[48.718]: master offset          1 s2 freq  +83710 path delay       485
ptp4l[48.844]: master offset          1 s2 freq  +83710 path delay       485
ptp4l[48.969]: master offset         -5 s2 freq  +83702 path delay       485
ptp4l[49.094]: master offset          3 s2 freq  +83712 path delay       485
ptp4l[49.219]: master offset          4 s2 freq  +83714 path delay       485
ptp4l[49.344]: master offset         -5 s2 freq  +83702 path delay       485
ptp4l[49.469]: master offset          3 s2 freq  +83713 path delay       487
====================

Signed-off-by: David S. Miller <davem@davemloft.net>