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SubjectRe: [PATCH] IDE 58
On Wed, 8 May 2002, Martin Dalecki wrote:
> BTW> I would really love it if the cris architecture people could
> "lend me" some small developement system for they interresting CPU.

We'll consider it :) However,

> This unfortunately is the somehow most wired ATA interface
> around. Which is due to the fact that the interface cell is directly mapped to
> some CPU registers. As a CPU design I think it's a fine approach. Don't
> take me wrong. You save yourself the whole silicon which is needed
> for BM access arbitration and general handling and so on... Very nice tought
> out. But on the software side this is a bit wired, since you can't use
> the generic I/O primitives of the arch in question.

I don't see why all IDE-interfaces in the world have to be I/O-mapped just
because the first PC implementations used that. Sure it was an extended
ISA-bus but the ISA bus is long gone and we don't all run PC's anymore
either.

So the simple abstraction we need to hit IDE-bus registers is a macro or
inline, instead of a call of an I/O-primitive. It was too much work to
abstract this when I inserted the CRIS-arch IDE-driver in the first place
so I found a workaround but now seems like a better time..

Similarily, there is no reason at all why the CPU has to do _polling_ just
because the IDE _bus_ is using a PIO-mode. It probably does that on legacy
PC's but HW designed, hrm, more optimally can use DMA. Hence the hooks for
the ide_func_t.

So I'd figure the software side really would be _easier_ to implement with
those assumptions about how an IDE-interface is supposed to work gone.

> This makes my cleanup of the portability layer a bit hard
> to finish on the software side.

I understand that, so lets keep the discussion going and I'll check over
your current cleanup.

/Bjorn


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