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l : linux-m68k@vger.kernel.org 24 February 2008 • 8:20AM -0500

Re: mac_esp bus error handling, was Re: setjmp/longjmp?
by Finn Thain

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On Sat, 23 Feb 2008, Michael Schmitz wrote:

> Hi,
>
> > > The only missing bit is to skip the writeback, as the fault has to
> > > be first fixed by the caller, so the patch below should do the
> > > trick...
> >
> > It does indeed do the trick! Thanks, Roman.
>
> No more access faults from kernel space possible this way?

The faults are all generated by accesses to the PDMA glue logic I/O
register; that address would be in kernel space.

> What happens with PDMA commands that fail during error processing -
> won't that command data belong in kernel space?

esp->command_block is in kernel space too but I don't know what the
implications are for handling faults. I have had to use the chip's
transfer count to determine where to resume a sequence of writes to the
I/O register following a fault. Apparently a bus error on a read from the
I/O register prevents the post-increment on the destination address, so
resuming is simpler.

>
> Otherwise, great job, Finn!

Thanks!

-f

>
> Cheers,
>
> Michael
>
>
>
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