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

Suzuki Kuruppassery Poulose
2019-12-02T10:44:05Z

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>