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 12:08 +0100, ysgrifennodd Chris Pringle:
>   
>>> 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.
>>     
>
> That I wonder about. The power management stuff and some other things
> that matter for timing are different however.
>   
We don't use any kind of power management (not compiled in) as our 
systems are always on... Is there any timing related options in the 
kernel config you'd recommend I look at?
>   
>> I'll give the interrupt disabling a go...
>>     
>
> Its just a guess but if you have low latency stuff, you have pre-empt
> enabled and you actually depend upon the semantics of inb_p/outb_p
> giving delays reliably then I'm not convinced are guarantees are strong
> enough
>
> Specifically we don't have any pre-empt protection between the I/O delay
> and the I/O so we could violate it as we don't have pre-empt disables in
> inb_p/outb_p and if your CPU context switch is quick enough it could
> trigger a problem.
>
> Alan
>
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>   
Okay, I've tried disabling both preemption and interrupts (separately, 
and together) and its still hanging...

I've had the Celeron systems being thrashed for well over 4 days now, 
and they are working fine... Why would the VIA system be any different? 
They have a slightly different CPU speed (the VIAs are 1000MHz, whereas 
the Celerons are 850MHz), but I would expect them to be fully compatible 
otherwise... unless its a microcode bug?

Any more ideas? Do you think writing to port 0x80 could be causing issues?

Thanks,
Chris

-- 

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Chris Pringle
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