Re: [Xenomai-core] 16550A driver and Moxa card / solved

[Jan Kiszka <jan.kiszka@domain.hid>]

[-- Attachment #1: Type: text/plain, Size: 2184 bytes --]

CHABAL David wrote:
> Le 11/5/2007, "Jan Kiszka" <jan.kiszka@domain.hid> a écrit:
> 
>> Maksym Veremeyenko wrote:
>>> CHABAL David пишет:
>>>
>>>> I met some trouble with the 16550A driver provided in Xenomai 2.3.1
>>>> and my Moxa cards (PCI / 8 * RS232 / 168U ).
>>>>
>>>> It was a problem of baudrate computation before setting the LCR_DLAB
>>>> register.
>>>>
>>>> The formula implemented by the Xenomai driver is different from the one
>>>> provided by Moxa. So I copy/paste the formula from the mxser.c file
>>>> (present in the
>>>> kernel distro), and it seems to work fine.
>>>>
>>>> I think it's Moxa card dependant, may be caused by the high default baud
>>>> rate of this card.
>>> I have two Moxa boards with no problem, possible you need to specify 
>>> 'baud_base' param.
>>>
>>> I my case :
>>>
>>> # 8 ports board:
>>> /sbin/modprobe xeno_16550A \
>>> ioaddr=0x1000,0x1008,0x1010,0x1018,0x1020,0x1028,0x1030,0x1038 \
>>> irq=9,9,9,9,9,9,9,9 \
>>> baud_base=921600,921600,921600,921600,921600,921600,921600,921600
>>>
>>> # 2 ports board + onboards:
>>> /sbin/modprobe xeno_16550A ioaddr=0x3f8,0x2f8,0xdf00,0xdf08 
>>> irq=4,3,11,11 baud_base=115200,115200,921600,921600
>>>
>> Interesting. That would leave us just with the generic fix to catch
>> baud_rate==0. Far more attractive. :)
>>
>> David, can you confirm this? Weren't you just aware of the baud_base
>> parameter?
> 
> I'm not totally convinced because if I compute by hand the DLAB register
> with the 19200 value (my config):
> 
> With the moxa driver:
>   baud_div = 912.600 / 19.200 = 47
> 
> With the Xeno driver:
>   baud_div = (912.600 - 9600) / 19.200 = 47
> 
> Grrr, it's ok here because the rounded values are the same because the
> baud base is biggest than the speed requested, but I think a problem can
> occur with 115200 or more, example:
> 
> moxa: 912.600/115.200 = 8
> xeno: = 7

Yeah, hard arguments. This really cries for a moxa tweak. (The
alternative would be to pass an artificially increased baud_base - but
that would be _really_ ugly and we could also ask the user for the
divider directly...)

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]