Re: [PATCH] Exar quad port serial

Lennart Sorensen
2006-10-18T13:34:59Z

On Tue, Oct 17, 2006 at 08:00:17PM -0500, Paul B Schroeder wrote:
> Sorry for the late response.. Here is a fuller explanation. Maybe
> somebody out there has a better solution:
>
> This is on our "Envoy" boxes which we have, according to the documentation,
> an "Exar ST16C554/554D Quad UART with 16-byte Fifo's". The box also has
> two other "on-board" serial ports and a modem chip.
>
> The two on-board serial UARTs were being detected along with the first two
> Exar UARTs. The last two Exar UARTs were not showing up and neither was
> the modem.
>
> This patch was the only way I could the kernel to see beyond the standard
> four serial ports and get all four of the Exar UARTs to show up.
>
> I hope this explains it well enough..

I suspect all you have to do might be to change how many ports it looks
for. The default max ports is 4 I believe on many kernel versions.

Look for CONFIG_SERIAL_8250_NR_UARTS and
CONFIG_SERIAL_8250_RUNTIME_UARTS in the kernel config.

If that doesn't work and you do need a special driver, at least label it
with more detail like 'for exar st16c554 quad uart' or 'for envoy board'
or whatever makes it clear which hardware it is for. I use exar pci
uarts (exar XR17d15[248] chips) which work fine already with the 8250
driver, or optionally with the jsm driver with a small change to the
list if pci identifiers. THey of course would not work with your driver
since they are completely different exar chips (even though one is also
a quad uart, although 64byte fifo).

--
Len Sorensen