Re: [IBM] RE: [BUG] Fusion MPT Base Driver initialization failure wit h kdum p

[Vivek Goyal <vgoyal@in.ibm.com>]

On Mon, Jul 25, 2005 at 03:10:33PM -0700, Andrew Morton wrote:
> Vivek Goyal <vgoyal@in.ibm.com> wrote:
> >
> > > If you don't stop the DMA engines before you boot the new kernel, the
> >  > addresses they have to send data to will now be random points in that
> >  > kernel's memory, leading to potential corruption of the new kernel
> >  > image.
> > 
> >  [Copying it to fastboot and linux-kernel mailing lists]
> > 
> >  We are booting second kernel (capture kernel) from a reserved memory location
> >  to take care of on-going DMA issues. So even if some DMA transactions are going
> >  on after the crash they will not corrupt the new kernel.
> > 
> >  > 
> >  > The interrupt panic of the fusion is probably a symptom of this: I bet a
> >  > DMA transfer has just completed and the interrupt is to inform us of
> >  > this (however, in the new kernel we're not expecting any transfers).
> > 
> >  That might very well be the case. So driver should simply ignore the interrupt
> >  when it is not expecting it or it should reset the device if it finds that 
> >  some interrupts are pending when it should not have been there.
> > 
> >  Basically it is a matter of hardening the driver so that it can handle/
> >  initialize the device even if the device is not in reset state. 
> 
> I'd expect that a lot of these problems could be reduced by simply pausing
> for a while in the crash handler, wait for I/O to complete.
> 

Andrew, We will test it out and see if it helps on some of the already
reported issues.

Thanks
Vivek
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