Re: OXuPCI952 and baud_base questions

[Matthias Reichl <hias@horus.com>]

Hi Greg!

On Wed, Dec 01, 2010 at 02:16:04PM -0800, Greg KH wrote:
> On Wed, Dec 01, 2010 at 05:46:34PM +0100, Matthias Reichl wrote:
> > I've got a Lindy 51237 multi I/O card (2 16C950 URATs up to 921kbit
> > plus one parallel port) with a Oxford OXuPCI952 chip (PCI vendor
> > ID 0x1415, device ID 0x9505).
> > 
> > http://www.lindy-international.com/2-port-rs-232-serial-1-port-parallel-card-pci/51237.html
> > http://www.plxtech.com/products/uart/oxupci952
> > 
> > Kernel 2.6.36.1 doesn't contain any device-specific configuration,
> > the "guess code" detects both UARTs at BAR0 and BAR1,
> > but with the wrong baudrate (default of 115200 instead of
> > 921600 needed for this card).
> > 
> > The card doesn't report any specific (sub-) vendor/device IDs but
> > the generic Oxford IDs. So adding an entry to the pci_device_id
> > table with a pbn_b0_bt_2_921600 config might break some prior
> > working setups (OXuPCI952 with baud_base=115200).
> > 
> > Do you have any policy how to cope with such situations?
> 
> Always set the baud rate to a valid one before using the tty port?

Sorry, I meant baud_base (or base_baud in 8250_pci.c), not baudrate :-(

Since the baud_base is differing (115200 instead of 921600)
setting a baudrate of X results in an actual baudrate of X*8 for
this card.

It's no problem for me to do a "setserial ... baud_base=921600"
or pass a module/kernel parameter to circumvent the problem,
but it sure would be nicer if the kernel would have set
the baud_base correctly.

The problem I'm seeing here is that this card is using a stock
OXuPCI952, which can be equipped with any oscillator, and doesn't
report any vendor-specific PCI IDs that lets it be distinguished
from other stock OXuPCI952 cards - otherwise I've just sent
a "[PATCH] Add support for Lindy 51237" to set baud_base=921600
for this specific card.

Personally, all 16C950 (compatible) cards I've bought so far
were capable of a max. 921kbit/sec (and thus had a baud_base of 921600).
So the current default of 115200 doesn't quite match my setup.
If I only need a card capable of 115200 bit/sec I usually buy
a standard 16550 card (not a 16C950).

So, my question is: would you include a patch in the kernel
to change the default baud_base from 115200 to 921600 for
the OXuPCI952 chip (1415:9505)?

so long,

Hias