Hi, one small typo/spello below... On 10/5/18 5:43 AM, Alexander Shishkin wrote: > Add a document describing MIPI SyS-T protocol driver usage. > > Signed-off-by: Alexander Shishkin <alexander.shish...@linux.intel.com> > Tested-by: Mathieu Poirier <mathieu.poir...@linaro.org> > --- > Documentation/trace/sys-t.rst | 62 +++++++++++++++++++++++++++++++++++ > 1 file changed, 62 insertions(+) > create mode 100644 Documentation/trace/sys-t.rst > > diff --git a/Documentation/trace/sys-t.rst b/Documentation/trace/sys-t.rst > new file mode 100644 > index 000000000000..3d8eb92735e9 > --- /dev/null > +++ b/Documentation/trace/sys-t.rst > @@ -0,0 +1,62 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +=================== > +MIPI SyS-T over STP > +=================== > + > +The MIPI SyS-T protocol driver can be used with STM class devices to > +generate standardized trace stream. Aside from being a standard, it > +provides better trace source identification and timestamp correlation. > + > +In order to use the MIPI SyS-T protocol driver with your STM device, > +first, you'll need CONFIG_STM_PROTO_SYS_T. > + > +Now, you can select which protocol driver you want to use when you create > +a policy for your STM device, by specifying it in the policy name: > + > +# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/ > + > +In other words, the policy name format is extended like this: > + > + <device_name>:<protocol_name>.<policy_name> > + > +With Intel TH, therefore it can look like "0-sth:p_sys-t.my-policy". > + > +If the protocol name is omitted, the STM class will chose whichever
s/chose/choose/ > +protocol driver was loaded first. > + > +You can also double check that everything is working as expected by > + > +# cat /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/protocol > +p_sys-t > + > +Now, with the MIPI SyS-T protocol driver, each policy node in the > +configfs gets a few additional attributes, which determine per-source > +parameters specific to the protocol: > + > +# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default > +# ls /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default > +channels > +clocksync_interval > +do_len > +masters > +ts_interval > +uuid > + > +The most important one here is the "uuid", which determines the UUID > +that will be used to tag all data coming from this source. It is > +automatically generated when a new node is created, but it is likely > +that you would want to change it. > + > +do_len switches on/off the additional "payload length" field in the > +MIPI SyS-T message header. It is off by default as the STP already > +marks message boundaries. > + > +ts_interval and clocksync_interval determine how much time in milliseconds > +can pass before we need to include a protocol (not transport, aka STP) > +timestamp in a message header or send a CLOCKSYNC packet, respectively. > + > +See Documentation/ABI/testing/configfs-stp-policy-p_sys-t for more > +details. > + > +* [1] https://www.mipi.org/specifications/sys-t > -- ~Randy