On Mon, Nov 24, 2008 at 02:55:42AM +0100, Michael Schmitz wrote:
We probably should have an SCC/ESCC core driver the way we have for
a lot of the other common chips like 8390 ethernet or ESP SCSI. I
know there's lots of systems with these chips that each have drivers.
Didn't seem too many of those in drivers/serial ...
I must admit I didn't go count them.
Most of the m68k mac serial quirks are the same as the ones in the
pmac serial driver. There is only one interrupt for both ports, but
According to my 2.2.25 source, SCC A is at interrupt number 33, SCC B is
at 34. Did that change with tha A/UX interrupt style?
No, those are synthetic interrupt sources. If you look at the interrupt
code, there is a fake interrupt controller registered on IRQ 4 that
looks at the SCC status bits and triggers the correct interrupt. Take
a look at mac_scc_dispatch in arch/m68k/mac/macints.c for details. The
pmac_zilog code does it a little different by tying the two devices
together and only registering for one interrupt and passing them off.
What seems to be true is all interrupt types for a given channel go to
the same handler...
That is definitely true on any Mac. Apple was generally stingy with
interrupt sources. For example, some mac systems don't even have a
real IRQ per NuBus slot even though they do all at least have a way
to detect which slot asserted the interrupt.
The platform device would need to have one interrupt number each for TX, RX,
status and special condition for each channel, plus data/control ports forr
each, plus flags. The Mac platform device would have only one interrupt per
channel (and perhaps a flag indicating that).
I'm sure we could do something like that with flags.
built-in modems need enable/disable code for that on m68k macs
Are there any Macs with builtin modems in the standard configuration?
It depends on what you mean by standard configuration. Some PowerBooks
shipped with internal modems, but I don't think there is any model
that always had one. It was an option on most later m68k PowerBooks
while most early ppc PowerBooks always had an internal modem.
There isn't much m68k mac specific, and I don't think the issues
you mention for Atari are issues on macs. The AV systems have
DMA but don't have a tx-dma channel for the second port. The one
interrupt is hooked up to IRQ 4, which means it doesn't go through
This is on AV Macs only (because the PSC interrupts are at 32-35 there)?
The AV Macs are quite a bit different from an IRQ perspective. They
don't hook much of anything up directly, so the layout is slightly more
logical. In particular, the registration of mac_scc_dispatch to IRQ 4
is conditionalized on !psc_present to exclude the AV models. It's all
the models using VIA1 as the main interrupt controller that need it.
The SCC interrupt line is never hooked up to a VIA chip, but it is
connected to the PSC on AV macs and the SCC IOP on the IIfx. Sorry
if the way I wrote this was confusing.
We could probably do something along those lines, but I can't see
tying it directly to the platform bus. I think it would be better
to make a zilog SCC/ESCC core driver and write a driver for each
bus interface type the way the ESP driver now works. It just seems
simpler from a code maintenance perspective.
I don't think using callbacks would be a clean way of handling this, so your
idea may be better.
It's hard to say for sure without trying it to see how it turns out.
VME and Atari used to use the same driver in 2.2 so that should still be
possible now.
Seems reasonable.
Brad Boyer
flar@xxxxxxxxxxxxx
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