[J-core] Checking in.

[Rob Landley]

On 12/7/19 12:24 AM, D. Jeff Dionne wrote:
> PPP is a supported protocol (of course) and is easy to get going.
> 
> By default, Turtle soft SoC has only a console uart, but it is relatively easy
> to add as many as you want to any gpio pins.  The in repo choices are UARTlite
> (compatible) and 16550 (compatible), and there are Linux drivers for both.  I
> don’t think the 16550 driver has been tested since J2 support changed to device
> tree... but otherwise there should be no surprises to get going on turtle (SoC
> and Linux sides).

FYI the UARTlite is much smaller from a circuitry perspective, but it operates
at a fixed speed (hardwired at build time, you can't change it from Linux) and
has a small buffer so you can't run it _that_ fast.

If I recall the 16550 implementation is code we got from somewhere else, which
works (and is reasonably licensed), but... isn't the cleanest. It's a good
option to _have_, but mostly we just use uartlite. (We've talked about
increasing the buffer size so it can go faster, but I don't think we actually
did it yet? It's on the todo list, but... we have ethernet.)

Rob