Re: About forcing 32bit DMA patch for AMD690G(SB600)

[Tejun Heo <htejun@gmail.com>]

Hello, Shane.  Sorry about the delay.  Got caught up in other stuff.

Shane Huang wrote:
> Quoting Tejun:
>> Uh-oh, wait a bit. Nope. Until we figure out what the something
>> else
> is
>> and positively verify 64bit DMA works fine, the quirk stays in.
> 
> Our HW engineer has confirmed that our SB600 SATA controller indeed
> has some MSI issue, and we do not have any workaround.
> 
> The workaround "quirk_msi_intx_disable_bug" to SB700 SATA controller 
> can NOT work to SB600 SATA controller in my debug, while disablement
> to RS690 MSI in kernel source can fix it.

Hmmm... Okay.  Is the SB600 SATA controller culprit or the north bridge
- RS690?  If the former is the case, proper way to work around it is to
add AHCI_HFLAG_NO_MSI for SB600 AHCI.

> As to the SB600 64 bit DMA capacity, do you have any methods to do 
> further verification? I do NOT find any problem in my debug after I
> disabled RS690 MSI in kernel 2.6.24-rc7.

The problem is that we didn't actually prove anything.  In the tests
you've done, pci=nomsi didn't fix the problem but disable_all_msi quirk
did.  pci=nomsi and disable_all_msi quirk are identical.  Also,
Srihari's problem was not reproduced, so currently we can't say much
from the test results.  Srihari, do you still have the system around?

Thanks.

-- 
tejun