tree 0de7f3932f23e8011f33a9b076da2b22d3f0d03e
parent 6cc20110913878ddb1a917f5aca03f648ce3f056
author Rupert Swarbrick <rswarbrick@lowrisc.org> 1587565642 +0100
committer weicaiyang <49293026+weicaiyang@users.noreply.github.com> 1588009004 -0700

[dv] Allow dv_lib-based sequences to have different RSP/REQ types

Most UVM sequences just send items and don't receive any response:

    start_item(req);
    `DV_CHECK_RANDOMIZE_FATAL(req)
    finish_item(req);

However, sometimes a driver needs to report what happened. For
example, there might have been some sort of error on the bus which
will affect the next sequence item to send. In this case, the driver
calls

    seq_item_port.item_done(rsp);

and the sequencer's code looks like

    start_item(req);
    `DV_CHECK_RANDOMIZE_FATAL(req)
    finish_item(req);
    get_response(rsp);
    // Do something based on rsp...

But what type is rsp? Sometimes, it's enough to send the request item
back. This works nicely when the sequence items are actually
pipelined (so that the sequence can figure out what item finished).
Sometimes, however, you might want to use a different type from the
request type - it's a bit of a bodge just to add another field to the
request for a "back channel".

To support this, many UVM classes are parameterised by "REQ" and
"RSP": the type of request and response item, respectively. Some of
the dv_lib code supported this already (dv_base_seq), but the
sequencer and driver base classes didn't.

This patch adds that support, defaulting to RSP = REQ. The ordering of
parameters looks a little odd, but it seems that lots of OpenTitan
code sets parameters by position, rather than name, so we have to add
any new optional parameter at the end of the list.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>