[gta02-core] Wasting valuable pins (Was: PMU cleanup)

[Werner Almesberger]

Rask Ingemann Lambertsen wrote:
> Other such examples are the DMA interface and the camera port.

I know that you like the camera port :-) But a good use for the DMA
interface is new to me. What would you do with it, considering that
all the address and data lines are buried somewhere in the PCB ?

>> (Ah, another task for the MPU: record the board revision :)
> 
>    Or we could have a serial/I2C EEPROM. It would allow much more fine
> grained board revision information, and as hardware fixed are applied (or
> hardware bugs are discovered - think bogus GTA02 earpiece capacitors), you
> could update the EEPROM to reflect the state of the board.

Oh, but the MPU could do that too. There's plenty of space left in
it to record extensive feature/bug lists :)

Anyway, that's something for after gta02-core. We already have a
lot more changes that I expected. Each change increases the risk
of gta02-core suffering some fatal flaw that will cripple it, and
that would be a really sad outcome.

>    But nGSM_OC is a bit like MODEM_RST and BT_PIO_5: It's allocated to a
> GPIO but is not used by the kernel[1] and two years after Neo 1973 release,
> still nobody misses it.

I also realize that nobody actually bothered to look if it was ever
asserted. Who knows, maybe the modem does go into overcurrent from
time to time, and we all think it's just a bit "unstable" ...

By the way, MODEM_RST is used for a reliable reflashing procedure.
The problem with it is that there were once issues with uncommanded
activation of these modem controls and the reset circuit was
therefore removed from some boards. Thus, you can't rely on it to
be present.

> Another signal that can go is nACCEL_CS now
> that we have only one accelerometer.

Very good point ! I've added it to ECN0016. If nobody can think of a
reason why we'd want to keep nACCEL_CS, I'll do the killing later
today.

- Werner