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

From: Vivek Goyal
Date: Tue Jul 26 2005 - 06:08:34 EST

On Mon, Jul 25, 2005 at 03:10:33PM -0700, Andrew Morton wrote:
> Vivek Goyal <vgoyal@xxxxxxxxxx> 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.

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