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 | 124 +++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 Documentation/networking/synce.rst
diff --git a/Documentation/networking/synce.rst b/Documentation/networking/synce.rst new file mode 100644 index 000000000000..a7bb75685c07 --- /dev/null +++ b/Documentation/networking/synce.rst @@ -0,0 +1,124 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================= +Synchronous Equipment Clocks +============================= + +Synchronous Equipment Clocks use a physical layer clock to syntonize +the frequency across different network elements. + +Basic Synchronous network node consist of a Synchronous Equipment +Clock (SEC) and and a PHY that has dedicated outputs of clocks recovered +from the Receive side and a dedicated TX clock input that is used as +a reference for the physical frequency of the transmit data to other nodes. + +The PHY is able to recover the physical signal frequency of the RX data +stream on RX ports and redirect it (sometimes dividing it) to recovered +clock outputs. Number of recovered clock output pins is usually lower than +the number of RX portx. As a result the RX port to Recovered Clock output +mapping needs to be configured. the TX frequency is directly depends on the +input frequency - either on the PHY CLK input, or on a dedicated +TX clock input. + + ┌──────────┬──────────┐ + │ RX │ TX │ + 1 │ ports │ ports │ 1 + ───►├─────┐ │ ├─────► + 2 │ │ │ │ 2 + ───►├───┐ │ │ ├─────► + 3 │ │ │ │ │ 3 + ───►├─┐ │ │ │ ├─────► + │ ▼ ▼ ▼ │ │ + │ ────── │ │ + │ ____/ │ │ + └──┼──┼────┴──────────┘ + 1│ 2│ ▲ + RCLK out│ │ │ TX CLK in + ▼ ▼ │ + ┌─────────────┴───┐ + │ │ + │ SEC │ + │ │ + └─────────────────┘ + +The SEC can synchronize its frequency to one of the synchronization inputs +either clocks recovered on traffic interfaces or (in advanced deployments) +external frequency sources. + +Some SEC implementations can automatically select synchronization source +through priority tables and synchronization status messaging and provide +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_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_STATE +To support multiple recovered clock outputs from the same port, this message +will return the IFLA_RCLK_STATE_COUNT attribute containing the number of +recovered clock outputs (N) and N IFLA_RCLK_STATE_OUT_STATE attributes +listing the output indexes with the respective GET_RCLK_FLAGS_ENA flag. +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. + + +Attributes: +IFLA_RCLK_STATE_COUNT - Returns the number of recovered clock outputs +IFLA_RCLK_STATE_OUT_STATE - Returns the current state of a single recovered + clock output in the struct if_get_rclk_msg. +struct if_get_rclk_msg { + __u32 out_idx; /* output index (from a valid range) */ + __u32 flags; /* configuration flags */ +}; + +Currently supported flags: +#define GET_RCLK_FLAGS_ENA (1U << 0) + + +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