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Diffstat (limited to 'Documentation/networking/timestamping.rst')
| -rw-r--r-- | Documentation/networking/timestamping.rst | 88 |
1 files changed, 68 insertions, 20 deletions
diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst index 5e93cd71f99f..7aabead90648 100644 --- a/Documentation/networking/timestamping.rst +++ b/Documentation/networking/timestamping.rst @@ -140,6 +140,14 @@ SOF_TIMESTAMPING_TX_ACK: cumulative acknowledgment. The mechanism ignores SACK and FACK. This flag can be enabled via both socket options and control messages. +SOF_TIMESTAMPING_TX_COMPLETION: + Request tx timestamps on packet tx completion. The completion + timestamp is generated by the kernel when it receives packet a + completion report from the hardware. Hardware may report multiple + packets at once, and completion timestamps reflect the timing of the + report and not actual tx time. This flag can be enabled via both + socket options and control messages. + 1.3.2 Timestamp Reporting ^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -158,7 +166,8 @@ SOF_TIMESTAMPING_SYS_HARDWARE: SOF_TIMESTAMPING_RAW_HARDWARE: Report hardware timestamps as generated by - SOF_TIMESTAMPING_TX_HARDWARE when available. + SOF_TIMESTAMPING_TX_HARDWARE or SOF_TIMESTAMPING_RX_HARDWARE + when available. 1.3.3 Timestamp Options @@ -193,6 +202,20 @@ SOF_TIMESTAMPING_OPT_ID: among all possibly concurrently outstanding timestamp requests for that socket. + The process can optionally override the default generated ID, by + passing a specific ID with control message SCM_TS_OPT_ID (not + supported for TCP sockets):: + + struct msghdr *msg; + ... + cmsg = CMSG_FIRSTHDR(msg); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_TS_OPT_ID; + cmsg->cmsg_len = CMSG_LEN(sizeof(__u32)); + *((__u32 *) CMSG_DATA(cmsg)) = opt_id; + err = sendmsg(fd, msg, 0); + + SOF_TIMESTAMPING_OPT_ID_TCP: Pass this modifier along with SOF_TIMESTAMPING_OPT_ID for new TCP timestamping applications. SOF_TIMESTAMPING_OPT_ID defines how the @@ -266,6 +289,23 @@ SOF_TIMESTAMPING_OPT_TX_SWHW: two separate messages will be looped to the socket's error queue, each containing just one timestamp. +SOF_TIMESTAMPING_OPT_RX_FILTER: + Filter out spurious receive timestamps: report a receive timestamp + only if the matching timestamp generation flag is enabled. + + Receive timestamps are generated early in the ingress path, before a + packet's destination socket is known. If any socket enables receive + timestamps, packets for all socket will receive timestamped packets. + Including those that request timestamp reporting with + SOF_TIMESTAMPING_SOFTWARE and/or SOF_TIMESTAMPING_RAW_HARDWARE, but + do not request receive timestamp generation. This can happen when + requesting transmit timestamps only. + + Receiving spurious timestamps is generally benign. A process can + ignore the unexpected non-zero value. But it makes behavior subtly + dependent on other sockets. This flag isolates the socket for more + deterministic behavior. + New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate regardless of the setting of sysctl net.core.tstamp_allow_data. @@ -493,8 +533,8 @@ implicitly defined. ts[0] holds a software timestamp if set, ts[1] is again deprecated and ts[2] holds a hardware timestamp if set. -3. Hardware Timestamping configuration: SIOCSHWTSTAMP and SIOCGHWTSTAMP -======================================================================= +3. Hardware Timestamping configuration: ETHTOOL_MSG_TSCONFIG_SET/GET +==================================================================== Hardware time stamping must also be initialized for each device driver that is expected to do hardware time stamping. The parameter is defined in @@ -507,12 +547,14 @@ include/uapi/linux/net_tstamp.h as:: }; Desired behavior is passed into the kernel and to a specific device by -calling ioctl(SIOCSHWTSTAMP) with a pointer to a struct ifreq whose -ifr_data points to a struct hwtstamp_config. The tx_type and -rx_filter are hints to the driver what it is expected to do. If -the requested fine-grained filtering for incoming packets is not -supported, the driver may time stamp more than just the requested types -of packets. +calling the tsconfig netlink socket ``ETHTOOL_MSG_TSCONFIG_SET``. +The ``ETHTOOL_A_TSCONFIG_TX_TYPES``, ``ETHTOOL_A_TSCONFIG_RX_FILTERS`` and +``ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS`` netlink attributes are then used to set +the struct hwtstamp_config accordingly. + +The ``ETHTOOL_A_TSCONFIG_HWTSTAMP_PROVIDER`` netlink nested attribute is used +to select the source of the hardware time stamping. It is composed of an index +for the device source and a qualifier for the type of time stamping. Drivers are free to use a more permissive configuration than the requested configuration. It is expected that drivers should only implement directly the @@ -531,9 +573,16 @@ Only a processes with admin rights may change the configuration. User space is responsible to ensure that multiple processes don't interfere with each other and that the settings are reset. -Any process can read the actual configuration by passing this -structure to ioctl(SIOCGHWTSTAMP) in the same way. However, this has -not been implemented in all drivers. +Any process can read the actual configuration by requesting tsconfig netlink +socket ``ETHTOOL_MSG_TSCONFIG_GET``. + +The legacy configuration is the use of the ioctl(SIOCSHWTSTAMP) with a pointer +to a struct ifreq whose ifr_data points to a struct hwtstamp_config. +The tx_type and rx_filter are hints to the driver what it is expected to do. +If the requested fine-grained filtering for incoming packets is not +supported, the driver may time stamp more than just the requested types +of packets. ioctl(SIOCGHWTSTAMP) is used in the same way as the +ioctl(SIOCSHWTSTAMP). However, this has not been implemented in all drivers. :: @@ -578,9 +627,10 @@ not been implemented in all drivers. -------------------------------------------------------- A driver which supports hardware time stamping must support the -SIOCSHWTSTAMP ioctl and update the supplied struct hwtstamp_config with -the actual values as described in the section on SIOCSHWTSTAMP. It -should also support SIOCGHWTSTAMP. +ndo_hwtstamp_set NDO or the legacy SIOCSHWTSTAMP ioctl and update the +supplied struct hwtstamp_config with the actual values as described in +the section on SIOCSHWTSTAMP. It should also support ndo_hwtstamp_get or +the legacy SIOCGHWTSTAMP. Time stamps for received packets must be stored in the skb. To get a pointer to the shared time stamp structure of the skb call skb_hwtstamps(). Then @@ -761,11 +811,9 @@ Documentation/devicetree/bindings/ptp/timestamper.txt for more details. 3.2.4 Other caveats for MAC drivers ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Stacked PHCs, especially DSA (but not only) - since that doesn't require any -modification to MAC drivers, so it is more difficult to ensure correctness of -all possible code paths - is that they uncover bugs which were impossible to -trigger before the existence of stacked PTP clocks. One example has to do with -this line of code, already presented earlier:: +The use of stacked PHCs may uncover MAC driver bugs which were impossible to +trigger without them. One example has to do with this line of code, already +presented earlier:: skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS; |