I was studying the design of the serial port and the N2HET device on the
TMS570, and emulating that in QEMU is not really an option. Since
that's how the debug serial port is done and perhaps how some I2C
devices are accessed, it doesn't make sense to do the QEMU emulator.
Just for details on this, the N2HET is a separate coprocessor, and would
require writing an instruct set front end to work properly, or writing
an emulator of some kind. That's a pretty big job in QEMU, but it could
be done.
However, even if you got one of these working, it still wouldn't work
for our purposes. The way the N2HET is used, it's bit-banging (sending
and receiving a bit at a time) in and out serial and I2C data. That's
extremely timing dependent for serial (not so much for I2C), and an
emulator is not going to be able to do that easily. Again, it could be
done, but the code required to take the outputs of the N2HET and covert
it back to bytes would be hard.
It would be more feasible to emulate what the N2HET does in our
configuration, but that's not going to be accepted into QEMU, so
maintenance for this would fall on us.
Sorry for the bad news. It would have been nice to have this. Looks
like I'm going to need a board.
Note, as an aside, this kind of thing uses a lot of power. The SCI and
I2C devices on the TMS570 are likely to use a lot less power. Not all
TMS570 SOCs have an I2C, though.
-corey
