Re: What's the SB600 64-bit DMA problem?

[Tejun Heo <htejun@gmail.com>]

Mark Nelson wrote:
> On Sun, Sep 21, 2008 at 10:15 AM, George Spelvin <linux@horizon.com> wrote:
>> "Grant Grundler" <grundler@google.com> wrote:
>>> On Sat, Sep 20, 2008 at 8:17 AM, George Spelvin <linux@horizon.com> wrote:
>>>> I just got a couple of MSI KA92 (AMD 790FX-based) motherboards with
>>>> 8 GiB of RAM each.  I noticed on boot that the SB600 AHCI implementation
>>>> had a 32-bit DMA limitation, and looking in the archives, it
>>>> appears that folks from AMD think it doesn't need to be there.
>>> URL?
>>> Just want to be sure I'm looking at the same thread.
>> "About forcing 32bit DMA patch for AMD690G(SB600)"
>> http://marc.info/?t=120107450600001
> 
> It looks like the results from people testing it further never arrived...
> 
>>From git commit a878539ef994787c447a98c2e3ba0fe3dad984ec ("ahci:
> work around ATI SB600 h/w quirk"), it looks like the initial
> idea was to limit each command to a maximum of 255 sectors (but
> to still allow 64bit DMA), but according to a later commit
> (4cde32fc4b32e96a99063af3183acdfd54c563f0; "ahci: SB600
> workaround is suspect... play it safe for now") this did not
> solve the lockups. But there are references in the thread above
> to broken MSI on the SB600 possibly being the cause of the problem,
> and now that commit 22b5e7a74280deae560c20ee1a9b502b35181327
> ("ahci: SB600 ahci can't do MSI, blacklist that capability") has gone in
> maybe this is why you're able to get 64bit DMA working? (although
> we do need more hints on how to conclusively test this)

Hmm... I doubt MSI has anything to do with 64bit DMA but then again
anything is possible.  Shane, anything came out of the testing?

Thanks.

-- 
tejun