usb_updater: protocol version 6 (vendor commands over usb)
This patch introduces version 6 of the cr50 USB update protocol. This
version allows to multiplex TPM vendor and extension commands over the
same USB endpoint which is used for firmware updates.
When channeling TPM vendor commands the USB update frame looks as follows:
4 bytes 4 bytes 4 bytes 2 bytes variable size
+-----------+--------------+---------------+-----------+------~~~-------+
+ total size| block digest | EXT_CMD | Vend. sub.| data |
+-----------+--------------+---------------+-----------+------~~~-------+
Where 'Vend. sub' is the vendor subcommand, and data field is
subcommand dependent. The target tells between update PDUs and
encapsulated vendor subcommands by looking at the EXT_CMD value - it
is set to 0xbaccd00a and as such is guaranteed not to be a valid
update PDU destination address.
In the previous protocol versions target reset was requested by the
host sending a 4 byte PDU after the target receives the UPGRADE_DONE
message and moves the state machine to the 'awaiting_reset' state.
With the ability to transfer vendor commands, there is no need for the
target to have a special state for reset. The host can send the posted
or immediate reboot request using the appropriate vendor command.
As a result the 'awaiting_reset' state has been removed, the target
accepts vendor commands only when state machine is in the rx_idle
state.
Vendor command response size is not fixed, it is subcommand dependent.
In the current implementation the total size of the vendor command PDU
can not exceed 64 bytes, as there is no reassembly on the target side.
For backwards compatibility in case the target is running protocol
version earlier than 6, the 4 byte PDU is still sent to the target
after UPGRADE_DONE is sent.
BRANCH=none
BUG=chrome-os-partner:60013
TEST=tested updates on Reef and Gru, observed that it is possible to
update earlier versions of firmware, and that it is possible to
request immediate and posted reset (depending on the presence of
the -u flag in the usb_updater invocation).
Change-Id: I6ea9e9f742c96b8ab0670e9cec87a83cd47bb20e
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/414948
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
3 files changed
