Re: aic7xxx strange code

[Andi Kleen <ak@muc.de>]

Arjan van de Ven <arjanv@redhat.com> writes:

> On Thu, Jan 01, 2004 at 11:31:17PM +0100, Andi Kleen wrote:
>> Architecture                  pci_alloc_consistent uses
>> i386                          normal dma mask
> 				.... but clipped to 32 bit
>
>> most 64bit archs/old x86-64   hardcoded 0xffffffff
>> newer IA64/some x86-64        consistent dma mask (2) 
>> newest x86-64                 normal dma mask & consistent dma mask (1) (2)
>> old redhat IA64               hardcoded 0xffffffffffffffff (?)
>
> not just old RH; At least one old SuSE too :0 (in fact I found a previous
> report claiming this only affected SuSE but it seems we're in the same boat
> now)

Ok. Old IA64 in general @) Or rather IA64/HP, right?

>> 
>> (1) to be bug-to-bug compatible with i386, some drivers rely on that.
>> (2) consistent dma mask is normally equivalent to hardcoded 0xffffffff
>> because that is the default value
>>                                     
>> It's quite a mess unfortunately. Due to (2) the 64bit architectures
>> are consistent, except for that old IA64. But i386 doing something
>> different is quite a problem.
>
> but i386 will *never* return > 32 bit at least.

The problem occurs with smaller masks than 32bit (e.g. used by some
sound drivers). The driver sets the normal mask < 32bit and expects
the memory to be allocated GFP_DMA. But it isn't.

The right thing to do would be to set the consistent mask, but that won't
work on i386 without an ifdef :-/

-Andi