Re: [Linuxptp-devel] [PATCH v3 00/11] synce4l: add software for Synchronous Ethernet

[Aya L. <ay...@nv...>]

Hi,

Please elaborate regarding kernel API. I understood from the submission 
that you plan to start off with some vendor specific sysfs declared in 
the config file.
But I believe this is not the final goal, correct?
Do you have kernel patches for review?

Thanks,
Aya

On 6/9/2022 10:12 PM, Kubalewski, Arkadiusz wrote:
> -----Original Message-----
> From: Aya Levin via Linuxptp-devel <lin...@li...>
> Sent: Wednesday, June 8, 2022 10:31 AM
> 
>> On 5/30/2022 10:34 PM, Arkadiusz Kubalewski wrote:
>>> synce4l is a software implementation of Synchronous Ethernet (Sync-E)
>>> according to ITU-T Recommendation G.8264. The design goal is to provide
>>> logic to supported hardware by processing Ethernet Synchronization
>>> Messaging Channel (ESMC) and control Digital Phase Locked Loop (DPLL)
>> We should use EEC rather than DPLL (more abstract less HW related)
> 
> Sure, graet idea. Will fix it.
> 
>>> clock on Network Card Interface (NIC).
>>>
>>> Application can operate in two mutually exclusive modes. If both modes
>>> are configured simultaneously, the external input takes precedence over
>>> internal one (internal is disabled implicitly).
>> AFAIU there is one selection process which regards all the sources and
>> select according to the quality/priority.
>> What is the benefit of two mutually exclusive modes?
> 
> Yes that is true, but SyncE chain has to start somewhere, currently:
> - internal mode - the NIC is monitoring its ports and selects one to
>    recover the clock from
> - external mode - ports are not monitored at all, user provides
>    external signal which drives the EEC, once EEC-DPLL is in locked state
>    synce4l starts broadcasting its QL to the neighbour configured ports.
>    (QL value also user-configured, as only user knows QL of external signal used
>    to drive the EEC),
> 
> Basically, external mode here was similar to Grandmaster in PTP,
> at least that was our understanding of A.2 from Annex A of G.8264
> 
> I think this needs to be renamed to make it clear for everyone.
> 
> Annex A also says:
> "Synchronous Ethernet equipment shall support a selection mechanism that allows
> synchronization to be derived from the line (i.e., traffic-carrying
> interfaces), from external synchronization interfaces (i.e., provided by
> co-located equipment) or internally from the EEC."
> 
> So in fact, we shall have 3 mutually exclusive modes for a device.
> 
> We will change this config item to a name "input_mode", with possible string
> values:
> - "line"
> - "external"
> - "internal"
> 
> Altough new modes: "internal" and "external", will not differ in implementation
> from current "external_mode", as this requires preconfiguring device and
> explicitly defining the QL by the user (at least before proper in-kernel
> interface for controlling EEC-alike integrated circuits is introduced).
> 
> Does it make sense?
> 
>>>
>>> External input mode
>>> If synce4l is configured to run in "external input" mode, then DPLL
>>> needs to have external 1PPS source attached (GPS or another generator).
>>> In this scenario synce4l always broadcasts clock quality level (QL)
>>> defined in configuration file. Additionally, for this mode
>>> incoming Sync-E frames do not participate in best source selection
>>> algorithm for DPLL.
>>>
>>> Internal input mode
>> Lets use the standard (G.8264 - Annex A) naming of traffic reference
>> source. Internal may refer internal oscillator.
> 
> Sure, above answer is sufficient?
>   
>>> In "internal input" mode incoming Sync-E frames are processed and best
>>> clock source is extracted from the link having the best quality level.
>>> synce4l configures such "best quality" port as a source to recover
>>> clock for DPLL. The recovered QL is broadcasted to all other interfaces
>>> then. An external clock cannot be used in this mode.
>>>
>>> Hardware
>>> synce4l is not bound to any specific NIC hardware.
>> In this level HW should be hidden totally - please see my comment in
>> patch #5
> 
> I understand you are refering to the name of "DPLL", will change it to EEC.
> 
>>>
>>> Theoretically any NIC could be used for enabling Sync-E device in
>> Lets use SyncE and not Sync-E
> 
> Sure, can do that.
> 
>>> External input mode - the NIC in this mode is in leader role (similar
>>> to Grand Master role in PTP), providing its Quality Level information
>>> in ESMC frames to its neighbors.
>> How do we monitor the quality and validity of an external source?
> 
> Right now (we already know that DPLL naming all over the code and documentation
> shall change in future patches), validity is checked as a state of dpll (user
> configures a shell command "get_dpll_state_cmd" and its possible return
> values). If it is not "locked", the DNU QL is broadcasted through the
> configured ports, once "locked" the user-configured QL starts to be
> broadcasted.
> 
> The quality itself depends on "external" sources, so this is user-configurable.
> 
> Thank you,
> Arkadiusz
> 
>>> It will not syntonize to any of its neighbor ports, since RX frames
>>> are not monitored. Only other Sync-E enabled neighbor ports could
>>> recover clock from that peer and syntonize to it.
>>> Practically this mode shall be used only if the NIC PHY ports are fed
>>> with stable and reliable frequency clock, Quality Level values that are
>>> sent to the peers are configured by the user. This is user
>>> responsibility to decide and set proper Quality-Level value for the
>>> device, corresponding to the quality of frequency clock generator of
>>> used hardware.
>>>
>>> When enabling Internal input mode, the NIC must be a device that
>>> actually, supports Synchronous Ethernet, which means it is able to
>>> syntonize frequency of all configured ports within the device
>>> to one chosen port - clock is recovered from its RX path, then is fed
>>> to other ports with Phase-Locked Loop (PLL) circuit powering clock of
>>> other ports.
>>> The NIC driver or dedicated software must provide a user with ability
>>> to:
>>>
>>> obtain current state of a DPLL used to syntonize the ports
>>> select one of the ports as a candidate for clock recovery.
>>> Both abilities are configurable in config file - the user must provide
>>> a shell commands - as explained in manual and descriptions inside of
>>> example config file.
>>>
>>> Arkadiusz Kubalewski (11):
>>>     synce4l: add config knobs for SyncE
>>>     synce4l: add synce in interface and util code
>>>     synce4l: add esmc_socket interface
>>>     synce4l: add synce_clock interface
>>>     synce4l: add synce_dev interface
>>>     synce4l: add synce_dev_ctrl interface
>>>     synce4l: add synce_port interface
>>>     synce4l: add synce_port_ctrl interface
>>>     synce4l: add synce_msg interface
>>>     synce4l: add synce_transport interface
>>>     synce4l: add synce4l application
>>>
>>>    .gitignore                |    1 +
>>>    README.org                |    2 +
>>>    config.c                  |  197 +++++--
>>>    config.h                  |    8 +
>>>    configs/synce.cfg         |  194 +++++++
>>>    esmc_socket.c             |   99 ++++
>>>    esmc_socket.h             |   42 ++
>>>    interface.c               |   29 +-
>>>    interface.h               |   24 +
>>>    makefile                  |    9 +-
>>>    synce4l.8                 |  239 ++++++++
>>>    synce4l.c                 |  132 +++++
>>>    synce4l_README.md         |  194 +++++++
>>>    synce_clock.c             |  284 +++++++++
>>>    synce_clock.h             |   40 ++
>>>    synce_dev.c               |  622 ++++++++++++++++++++
>>>    synce_dev.h               |   64 ++
>>>    synce_dev_ctrl.c          |  153 +++++
>>>    synce_dev_ctrl.h          |   64 ++
>>>    synce_msg.c               |  259 +++++++++
>>>    synce_msg.h               |  174 ++++++
>>>    synce_msg_private.h       |   87 +++
>>>    synce_port.c              |  491 ++++++++++++++++
>>>    synce_port.h              |  184 ++++++
>>>    synce_port_ctrl.c         | 1161 +++++++++++++++++++++++++++++++++++++
>>>    synce_port_ctrl.h         |  165 ++++++
>>>    synce_transport.c         |  102 ++++
>>>    synce_transport.h         |   55 ++
>>>    synce_transport_private.h |   18 +
>>>    util.c                    |   22 +
>>>    util.h                    |    8 +
>>>    31 files changed, 5077 insertions(+), 46 deletions(-)
>>>    create mode 100644 configs/synce.cfg
>>>    create mode 100644 esmc_socket.c
>>>    create mode 100644 esmc_socket.h
>>>    create mode 100644 synce4l.8
>>>    create mode 100644 synce4l.c
>>>    create mode 100644 synce4l_README.md
>>>    create mode 100644 synce_clock.c
>>>    create mode 100644 synce_clock.h
>>>    create mode 100644 synce_dev.c
>>>    create mode 100644 synce_dev.h
>>>    create mode 100644 synce_dev_ctrl.c
>>>    create mode 100644 synce_dev_ctrl.h
>>>    create mode 100644 synce_msg.c
>>>    create mode 100644 synce_msg.h
>>>    create mode 100644 synce_msg_private.h
>>>    create mode 100644 synce_port.c
>>>    create mode 100644 synce_port.h
>>>    create mode 100644 synce_port_ctrl.c
>>>    create mode 100644 synce_port_ctrl.h
>>>    create mode 100644 synce_transport.c
>>>    create mode 100644 synce_transport.h
>>>    create mode 100644 synce_transport_private.h
>>>
>>