tree 37920d145b6c428d2e0ee65176db773b8613c4b0
parent 6f7094c7b1fc37b0a1955a04d3c259aab86d50c5
author Jes B. Klinke <jbk@chromium.org> 1655121172 -0700
committer cfrantz <frantzcj+github@gmail.com> 1663272183 -0700

[opentitantool] Add transport subcommand

UltraDebug and the CW310 Atmel chip both have firmware that hard-codes
the functionality of reset, uart, and all other pins, and are therefore
ready for operation upon powering on.

HyperDebug on the other hand, is not hard-coded for any OpenTitan pin
assignments, and all its ports default to high-impedance.  Hence, it
needs some initialization to be told among other things that the reset
pin should be open-drain with pullup, defaulting high, and the boot0
pins should be push-pull defaulting to a low level.  These pin
configurations and defaults are generally declared in configuration
files.  OpenTitan tool cannot blindly apply these defaults at every
invocation, as it would override any previous pin manipulation in the
session.

This PR introduces a new command `transport init`, meant to explicitly
tell the OpenTitan tool to configure all pins according to the
configuration, and set their level to the default (discarding any
previously set levels).

I have create the `transport` top-level command with the intent that
HyperDebug or other transports may have some special features that do
not fit well into any generic trait, and we could add a channel for
sending arbitrary instructions to the transport, without OpenTitan tool
understanding those instructions.  HyperDebug for instance already has a
textual command line interface, if it had a command for setting e.g. the
slope control on I2C or SPI lines, then OpenTitan tool could be fitted
with a `transport passthrough` command, allowing the sending of a text
string verbatim to the transport for processing.

Signed-off-by: Jes B. Klinke <jbk@chromium.org>
Change-Id: Ifd004b024a087beb91ae57268a87d02063af8e85