Re: [PATCH 02/02] sata_mv: warn on PIO with multiple DRQs

[Mark Lord <liml@rtr.ca>]

Jeff Garzik wrote:
> Mark Lord wrote:
>> Just about everything can do some form of DMA nowadays,
>> but regardless of that the sata_mv chipsets have errata
>> for PIO of anything more than a single sector.
>>
>> In practice, I haven't managed to trigger the issue here,
>> but the errata descriptions indicate that it should be a major
>> issue for any volume of multi-sector PIO commands.
> 
> 
> I need to review the state of PIO-multi, but IIRC it's not used by default.
> 
> We should be able to handle this errata without banning all PIO...
..

I'm not really all that worried about it.
But it affects *non multi* PIO as well -- anything that can generate
more than a single DRQ per command-issue.

So a READ_SECTORS or WRITE_SECTORS (pio) for anything more than
a single sector could do it, in theory.

If we *really* care, then I'll dig into it deeper in the next kernel.
It can be worked around in the IRQ handler, by taking great care in
the exact sequence of IRQ-arrival and DRQ-status checks.

Heck.. we might even have it right (by accident) today.

Cheers