Subject: Re: Parallel ATA with libata status with the patches I'm working on
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org
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Date: Sat, 05 Nov 2005 08:50:30 +1100
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On Fri, 2005-11-04 at 13:34 +0000, Alan Cox wrote:
> On Gwe, 2005-11-04 at 17:43 +1100, Benjamin Herrenschmidt wrote:
> > > - HPA
> > > - IRQ mask
> > 
> > Why do we need the above at all ? It always looked to me like a gross
> > hack but then, I don't fully understand what the problem was on those
> > old x86 that needed it :)
> 
> You can't do anything useful with some systems without disabling the HPA
> because it is used to mask most of the drive at boot to hide from old
> incompatible BIOS.

I know, I was talking about IRQ Mask :)

> IRQ mask is on my todo list and looks quite easy. A small number of
> controllers mishandle the case when the FIFO empties. Instead of
> stalling the drive they dribble random numbers. 

OK, but my question why, what is the reason why we need IRQ mask ? Some
old non-PCI controllers can't grok un-related ISA IO cycles during a
FIFO read/write ? I suppose those would be broken on SMP too (though I
suspect then that those don't exist as SMP machines then :)

Ben.


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