Re: [PATCH v5 13/14] docs: coresight: Update documentation for CoreSight to cover CTI.

[Suzuki Kuruppassery Poulose <suzuki.poulose@arm.com>]

On 19/11/2019 23:19, Mike Leach wrote:
> Add new document covering CTI / CTM usage in CoreSight.
> 
> Add section in coresight.rst introducing CTI and CTM modules with link
> to new document.
> 
> Signed-off-by: Mike Leach <mike.leach@linaro.org>
> ---
>   .../trace/coresight/coresight-ect.rst         | 200 ++++++++++++++++++
>   Documentation/trace/coresight/coresight.rst   |  13 ++
>   2 files changed, 213 insertions(+)
>   create mode 100644 Documentation/trace/coresight/coresight-ect.rst
> 
> diff --git a/Documentation/trace/coresight/coresight-ect.rst b/Documentation/trace/coresight/coresight-ect.rst
> new file mode 100644
> index 000000000000..6448cf910f20
> --- /dev/null
> +++ b/Documentation/trace/coresight/coresight-ect.rst
> @@ -0,0 +1,200 @@
> +=============================================
> +CoreSight Embedded Cross Trigger (CTI & CTM).
> +=============================================
> +
> +    :Author:   Mike Leach <mike.leach@linaro.org>
> +    :Date:     November 2019
> +

...


> +
> +Channels API Directory
> +~~~~~~~~~~~~~~~~~~~~~~
> +
> +This provides an easy way to attach triggers to channels, without needing
> +the multiple register operations that are required if manipluating the
> +'regs' sub-dir elements directly.
> +
> +A number of files provide this API::
> +
> +   >$ ls ./cti_sys0/channels/
> +   chan_clear         chan_inuse         chan_xtrigs_view      trigin_detach
> +   chan_free          chan_pulse         chan_xtrigs_view_sel  trigout_attach
> +   chan_gate_disable  chan_set           trig_filter_enable    trigout_detach
> +   chan_gate_enable   chan_xtrigs_reset  trigin_attach         trigout_filtered
> +
> +Most access to these elements take the form::
> +
> +  echo <chan> [<trigger>] > /<device_path>/<operation>
> +
> +where the optional <trigger> is only needed for trigXX_attach | detach
> +operations.
> +
> +e.g.::
> +
> +   >$ echo 0 1 > ./cti_sys0/channels/trigout_attach
> +   >$ echo 0 > ./cti_sys0/channels/chan_set
> +
> +Attaches trigout(1) to channel(0), then activates channel(0) generating a
> +set state on cti_sys0.trigout(1)
> +
> +
> +*API operations*
> +
> +   * ``trigin_attach, trigout_attach``: Attach a channel to a trigger signal.
> +   * ``trigin_detach, trigout_detach``: Detach a channel from a trigger signal.
> +   * ``chan_set``: Set the channel - the set state will be propogated around
> +     the CTM to other connected devices.
> +   * ``chan_clear``: Clear the channel.
> +   * ``chan_pulse``: Set the channel for a single CoreSight clock cycle.
> +   * ``chan_gate_enable``: Write operation sets the CTI gate to propagate
> +     (enable) the channel to other devices. This operation takes a channel
> +     number. CTI gate is enabled for all channels by default at power up. Read
> +     to list the currently enabled channels on the gate.
> +   * ``chan_gate_disable``: Write channel number to disable gate for that
> +     channel.
> +   * ``chan_inuse``: Show the current channels attached to any signal
> +   * ``chan_free``: Show channels with no attached signals.
> +   * ``chan_xtrig_view``: write a channel number to select a channel to view,
> +     read to show the cross triggers programmed for the selected channel.
> +   * ``trig_filter_enable``: Defaults to enabled, disable to allow potentially
> +     dangerous output signals to be set.
> +   * ``trigout_filtered``: Trigger out signals that are prevented from being
> +     set if filtering ``trig_filter_enable`` is enabled. One use is to prevent
> +     accidental ``EDBGREQ`` signals stopping a core.
> +   * ``chan_xtrigs_reset``: Write 1 to clear all channel / trigger programming.
> +     Resets device hardware to default state.
> +
> +e.g.::
> +
> +   .../cti_sys0/channels# echo 2 1 > trigin_attach
> +   .../cti_sys0/channels# echo 2 6 > trigout_attach

minor nit: It may be a good idea to add a comment to describe what you
are doing with the above operations, to avoid looking up and mapping it
for someone looking it up. I am not too keen, but it is definitely
helpful.

> +   .../cti_sys0/channels# cat chan_free
> +   0-1,3
> +   .../cti_sys0/channels# cat chan_inuse
> +   2
> +   .../cti_sys0/channels# echo 2 > chan_xtrigs_view
> +   .../cti_sys0/channels# cat chan_xtrigs_view
> +   [2] IN: 1 OUT: 6
> +   .../cti_sys0/# echo 1 > enable
> +   .../cti_sys0/channels# echo 2 > chan_set
> +   .../cti_sys0/channels# cat ../regs/choutstatus
> +   0x4
> +   .../cti_sys0/channels# cat ../regs/trigoutstatus
> +   0x40
> +   .../cti_sys0/channels# echo 2 > chan_clear

> +   .../cti_sys0/channels# cat ../regs/trigoutstatus
> +   0x0
> +   .../cti_sys0/channels# cat ../regs/trigoutstatus
> +   0x0

nit: duplicate lines ?

Otherwise:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>