Re: [Openvortex-dev] Findings...

[Manuel Jander]

Hi James,


Shamus wrote:

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> Hi all!
>
> I've finally been able to track down the problem on my machine with
> the ALSA driver. In vortex_interrupt(...) there is a call to
> snd_mpu401_uart_interrupt(...) and something in that call is causing
> the kernel panic (unable to dereference virtual address or some
> such--see previous email for exact wording).
>  
Great !

> I also found out the reason I was having trouble with the source code
> (so it seemed). It seems that (at least as of the 2.4.19 kernel) as
> soon as you call request_irq(...) that it starts calling the
> vortex_interrupt(...) function *immediately* and the source mask has
> the IRQ_TIMER bit set--not good! So anyway, if you don't clear this
> IRQ it keeps calling the IRQ handler until you acknowledge it. Since I
> had a return; statement above where it does
>
>         if (source & IRQ_TIMER)
>                 hwread(vortex->mmio, VORTEX_IRQ_STAT);
>
> it would simply keep calling the IRQ handler--effectively locking up
> the system. All *before* the driver had a chance to call
> vortex_core_init(chip)! I'm not sure why the call to
> snd_mpu401_uart_interrupt(...) is causing the crash, but at least I
> know where to look... BTW, the crash occurred *after* it returned from
> vortex_core_init(chip), when the card is supposed to be fully
> initialized.  :-/
>  
I agree. I expected the card wouldn't be doing anything before it was 
programmed to.
Imagine a soundcard capturing sound and writing it per DMA somewhere 
into memory ... very bad.
Maybe there some few Vortex card badly designed with such odd behaviour. 
Anyway,  our driver
has to deal with such situations.

Any sugestions ?

Manuel