Re: Kernel Summit request for Discussion of future of ATA (libata) and IDE

[Jeff Garzik <jeff@garzik.org>]

Robert Hancock wrote:
> Alan Cox wrote:
>>> * There are still corner case in libata core - PIO is dead slow
>>> compared to drivers/ide/,
>>
>> There are two there - libata keeps IRQs blocked for longer in PIO mode as
>> well which is a factor for realtime that needs looking at, as well as
>> using 16bit not 32bit I/O for most devices (which is trivial to fix). The
>> IRQ masking stuff is more complex and old IDE handles it far better for
>> PIO on non shared IRQ interfaces. That is actually probably the most
>> complicated thing to address of the stuff you'd want to do if you were
>> going to kill off old IDE.
> 
> I was looking into the 32-bit PIO issue a bit yesterday. It looks like 
> some of the VLB libata drivers are doing this internally already, so it 
> shouldn't be hard to do this in the core. Only question is how we know 
> generically if the controller can do it or not? It looks like in old 
> IDE, a few controllers explicitly disable it, but it appears that it 
> doesn't default to on for any controller, so it's possible there are 
> others on which it doesn't work. Presumably anything on an actual 16-bit 
> bus (ISA, LPC, etc.) wouldn't like it, to start with.

FWIW there is already a patch from Willy Terreau (sp?) to add 32-bit I/O.

I queued it for "later" because it had some issues that Alan pointed 
out, IIRC.  I definitely want to push it in, though.

	Jeff