| Message ID | 20211104081231.1982753-7-maciej.machnikowski@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Add RTNL interface for SyncE | expand |
On Thu, 4 Nov 2021 09:12:31 +0100 Maciej Machnikowski wrote: > +Synchronous Ethernet networks use a physical layer clock to syntonize > +the frequency across different network elements. > + > +Basic SyncE node defined in the ITU-T G.8264 consist of an Ethernet > +Equipment Clock (EEC) and can recover synchronization > +from the synchronization inputs - either traffic interfaces or external > +frequency sources. > +The EEC can synchronize its frequency (syntonize) to any of those sources. > +It is also able to select a synchronization source through priority tables > +and synchronization status messaging. It also provides necessary > +filtering and holdover capabilities. > + > +The following interface can be applicable to diffferent packet network types > +following ITU-T G.8261/G.8262 recommendations. Can we get a diagram in here in terms of how the port feeds its recovered Rx freq into EEC and that feeds freq of Tx on other ports? I'm still struggling to understand your reasoning around not making EEC its own object. "We can do this later" seems like trading relatively little effort now for extra work for driver and application developers for ever. Also patch 3 still has a kdoc warning.
> -----Original Message----- > From: Jakub Kicinski <kuba@kernel.org> > Sent: Thursday, November 4, 2021 7:09 PM > To: Machnikowski, Maciej <maciej.machnikowski@intel.com> > Subject: Re: [PATCH net-next 6/6] docs: net: Add description of SyncE > interfaces > > On Thu, 4 Nov 2021 09:12:31 +0100 Maciej Machnikowski wrote: > > +Synchronous Ethernet networks use a physical layer clock to syntonize > > +the frequency across different network elements. > > + > > +Basic SyncE node defined in the ITU-T G.8264 consist of an Ethernet > > +Equipment Clock (EEC) and can recover synchronization > > +from the synchronization inputs - either traffic interfaces or external > > +frequency sources. > > +The EEC can synchronize its frequency (syntonize) to any of those > sources. > > +It is also able to select a synchronization source through priority tables > > +and synchronization status messaging. It also provides necessary > > +filtering and holdover capabilities. > > + > > +The following interface can be applicable to diffferent packet network > types > > +following ITU-T G.8261/G.8262 recommendations. > > Can we get a diagram in here in terms of how the port feeds its > recovered Rx freq into EEC and that feeds freq of Tx on other ports? Will try - yet my ASCII art skills are not very well developed :) > I'm still struggling to understand your reasoning around not making > EEC its own object. "We can do this later" seems like trading > relatively little effort now for extra work for driver and application > developers for ever. That's not the case. We need EEC and the other subsystem we wanted to make is the DPLL subsystem. While EEC can be a DPLL - it doesn't have to, and it's also the other way round - the DPLL can have numerous different usages. When we add the DPLL subsystem support the future work will be as simple as routing the EEC state read function to the DPLL subsystem. But if someone decides to use a different HW implementation he will still be able to implement his own version of API to handle it without a bigger DPLL block > Also patch 3 still has a kdoc warning. Will fix.
On Fri, 5 Nov 2021 11:51:48 +0000 Machnikowski, Maciej wrote: > > I'm still struggling to understand your reasoning around not making > > EEC its own object. "We can do this later" seems like trading > > relatively little effort now for extra work for driver and application > > developers for ever. > > That's not the case. We need EEC and the other subsystem we wanted > to make is the DPLL subsystem. While EEC can be a DPLL - it doesn't have > to, and it's also the other way round - the DPLL can have numerous different > usages. We wanted to create a DPLL object to the extent that as a SW guy I don't understand the difference between that and an EEC. Whatever category of *PLL etc. objects EEC is, that's what we want to model. > When we add the DPLL subsystem support the future work will be as simple > as routing the EEC state read function to the DPLL subsystem. But if someone > decides to use a different HW implementation he will still be able to > implement his own version of API to handle it without a bigger DPLL block All we want is something that's not a port to hang whatever attributes exist in RTM_GETEECSTATE.
> -----Original Message----- > From: Jakub Kicinski <kuba@kernel.org> > Sent: Friday, November 5, 2021 10:30 PM > To: Machnikowski, Maciej <maciej.machnikowski@intel.com> > Subject: Re: [PATCH net-next 6/6] docs: net: Add description of SyncE > interfaces > > On Fri, 5 Nov 2021 11:51:48 +0000 Machnikowski, Maciej wrote: > > > I'm still struggling to understand your reasoning around not making > > > EEC its own object. "We can do this later" seems like trading > > > relatively little effort now for extra work for driver and application > > > developers for ever. > > > > That's not the case. We need EEC and the other subsystem we wanted > > to make is the DPLL subsystem. While EEC can be a DPLL - it doesn't have > > to, and it's also the other way round - the DPLL can have numerous > different > > usages. > > We wanted to create a DPLL object to the extent that as a SW guy > I don't understand the difference between that and an EEC. Whatever > category of *PLL etc. objects EEC is, that's what we want to model. The DPLL has more uses than just EEC. I.e. Timing card uses one to generate different frequencies synchronized to 1PPS coming from the GNSS receiver. Implementing the whole DPLL subsystem may be an overkill for some basic solutions that are embedded inside the PHY and only handle the syntonization of TX frequency to the RX one. In this case all they would report is the current state. > > When we add the DPLL subsystem support the future work will be as > simple > > as routing the EEC state read function to the DPLL subsystem. But if > someone > > decides to use a different HW implementation he will still be able to > > implement his own version of API to handle it without a bigger DPLL block > > All we want is something that's not a port to hang whatever attributes > exist in RTM_GETEECSTATE. Routing to the DPLL object will be a specific use-case required only if we support advanced cases with external sources of frequency (like an atomic clock).
diff --git a/Documentation/networking/synce.rst b/Documentation/networking/synce.rst new file mode 100644 index 000000000000..986b9e62809f --- /dev/null +++ b/Documentation/networking/synce.rst @@ -0,0 +1,88 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +Synchronous Ethernet +==================== + +Synchronous Ethernet networks use a physical layer clock to syntonize +the frequency across different network elements. + +Basic SyncE node defined in the ITU-T G.8264 consist of an Ethernet +Equipment Clock (EEC) and can recover synchronization +from the synchronization inputs - either traffic interfaces or external +frequency sources. +The EEC can synchronize its frequency (syntonize) to any of those sources. +It is also able to select a synchronization source through priority tables +and synchronization status messaging. It also provides necessary +filtering and holdover capabilities. + +The following interface can be applicable to diffferent packet network types +following ITU-T G.8261/G.8262 recommendations. + +Interface +========= + +The following RTNL messages are used to read/configure SyncE recovered +clocks. + +RTM_GETRCLKRANGE +----------------- +Reads the allowed pin index range for the recovered clock outputs. +This can be aligned to PHY outputs or to EEC inputs, whichever is +better for a given application. +Will call the ndo_get_rclk_range function to read the allowed range +of output pin indexes. +Will call ndo_get_rclk_range to determine the allowed recovered clock +range and return them in the IFLA_RCLK_RANGE_MIN_PIN and the +IFLA_RCLK_RANGE_MAX_PIN attributes + +RTM_GETRCLKSTATE +----------------- +Read the state of recovered pins that output recovered clock from +a given port. The message will contain the number of assigned clocks +(IFLA_RCLK_STATE_COUNT) and an N pin indexes in IFLA_RCLK_STATE_OUT_IDX +To support multiple recovered clock outputs from the same port, this message +will return the IFLA_RCLK_STATE_COUNT attribute containing the number of +active recovered clock outputs (N) and N IFLA_RCLK_STATE_OUT_IDX attributes +listing the active output indexes. +This message will call the ndo_get_rclk_range to determine the allowed +recovered clock indexes and then will loop through them, calling +the ndo_get_rclk_state for each of them. + +RTM_SETRCLKSTATE +----------------- +Sets the redirection of the recovered clock for a given pin. This message +expects one attribute: +struct if_set_rclk_msg { + __u32 ifindex; /* interface index */ + __u32 out_idx; /* output index (from a valid range) + __u32 flags; /* configuration flags */ +}; + +Supported flags are: +SET_RCLK_FLAGS_ENA - if set in flags - the given output will be enabled, + if clear - the output will be disabled. + +RTM_GETEECSTATE +---------------- +Reads the state of the EEC or equivalent physical clock synchronizer. +This message returns the following attributes: +IFLA_EEC_STATE - current state of the EEC or equivalent clock generator. + The states returned in this attribute are aligned to the + ITU-T G.781 and are: + IF_EEC_STATE_INVALID - state is not valid + IF_EEC_STATE_FREERUN - clock is free-running + IF_EEC_STATE_LOCKED - clock is locked to the reference, + but the holdover memory is not valid + IF_EEC_STATE_LOCKED_HO_ACQ - clock is locked to the reference + and holdover memory is valid + IF_EEC_STATE_HOLDOVER - clock is in holdover mode +State is read from the netdev calling the: +int (*ndo_get_eec_state)(struct net_device *dev, enum if_eec_state *state, + u32 *src_idx, struct netlink_ext_ack *extack); + +IFLA_EEC_SRC_IDX - optional attribute returning the index of the reference that + is used for the current IFLA_EEC_STATE, i.e., the index of + the pin that the EEC is locked to. + +Will be returned only if the ndo_get_eec_src is implemented. \ No newline at end of file
Add Documentation/networking/synce.rst describing new RTNL messages and respective NDO ops supporting SyncE (Synchronous Ethernet). Signed-off-by: Maciej Machnikowski <maciej.machnikowski@intel.com> --- Documentation/networking/synce.rst | 88 ++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 Documentation/networking/synce.rst