Re: Serial driver 8250 hangs the kernel with the VIA Nehemiah...

[Chris Pringle <chris.pringle@miranda.com>]

Alan Cox wrote:
> Ar Gwe, 2006-08-11 am 09:52 +0100, ysgrifennodd Chris Pringle:
>  
>> on it. However, when the port is receiving a lot of data, it has the
>> tendency to either get corrupted data, or to crash the kernel.
>>     
>
> What do the crash traces look like
>   

Sorry - the kernel hangs, not crashes. There is no output whatsoever 
after the hang - SysRq doesn't work, but Numlock does.
>  
>> The "inb" as it is will sometimes return bad data - I'm guessing this
>> is due to ISA bus instability... Anyway I changed it to "inb_p" which
>> cured the corruption problem, but has introduced another issue - it
>> hangs the kernel.
>>     
>
> Maybe you need to have a chat with your hardware guys. Certainly if
> inb_p makes a difference you've got hardware not software side problems.
>   
Perhaps - I'm in discussion with them at the moment, but neither our, 
nor their department have managed to come up with an answer yet.
>  
>> Interestingly, it only hangs on systems with a VIA Nehemiah CPU, the
>> Intel Celerons seem to work fine. Could this be a problem with writing
>> to that dreaded port 0x080 within inb_p?
>>     
>
> Unlikely as it would affect both. More likely would be that the ISA bus
> clock is generated off the PCI bus clock and you have one of the
> multipliers wrong or too high for the board.
>   
Thats interesting, but wouldn't this produce strange side affects for 
the 2.4 kernel as well? 2.4 works fine on both VIAs and Celerons.
>  
>> it only occur on the VIA chip and not the Celeron? I don't think the
>> problem is there when the low latency patches are not applied - so I'm
>> thinking it's probably a timing problem of some sort.
>>     
>
> That bit is interesting. Something really off the wall to try - disable
> interrupts around the inb_p(), especially if you are using pre-emption
> and let me know what happens.
>
> Alan
>
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>   
I'll give the interrupt disabling a go...

Thanks Alan.
Chris.

-- 

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Chris Pringle
Software Engineer

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