Re: [PATCH] 2.6.14-rc3 ixp4xx_copy_from little endian/alignment

[David Vrabel <dvrabel@cantab.net>]

John Bowler wrote:
> > Also, I've noticed that the PCI_CSR is mis-configured when the XScale 
> > core is in little-endian mode.  ABE (AHB is big-endian) /must/ always be 
> > set -- remember that the NPEs are always big-endian devices.
>
>
> This doesn't affect the flash (we've verified that - i.e. *with* the
> patch the flash works in LE regardless of the patch for the PCI_CSR
> setting).

Now that you mention it I do remember seeing this patch floating around.

> > Since I'd never run an IXP4xx in little-endian mode I've not looked at 
> > this issue in any great depth so I could be wrong here.  Regardless, the 
> > proposed hack to the flash map driver is wrong since all expansion bus 
> > peripherals are affected not just flash (i.e., the solution needs to be 
> > more generic rather than flash driver specific).
>
>
> No, that's incorrect.  The patch has been demonstrated to be correct with
> all devices (along with the PCI_CSR patch, which Deepak has already pushed
> upstream).  I.e. *without* the patch everything works (BE and LE) except
> the flash is unuseable, *with* the patch the flash works too.

It appears that the NSLU2 only has the flash on the expansion bus which 
is why you believe it's a flash specific problem.

> So I'm effectively saying we need data coherency in the flash, but what we
> have in everything *else* is working just find with address coherency.

Data coherency can be set on a per 1 Mibyte page basis so all other (APB 
and PCI) peripherals would continue to use address coherency and thus 
would continue to function as they are now.

David Vrabel
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