Re: [PATCH] pata_ali: Lots of problems still showing up with small ATAPI DMA

[Tejun Heo <htejun@gmail.com>]

Alan Cox wrote:
> On Wed, 28 Nov 2007 10:36:15 +0900
> Tejun Heo <htejun@gmail.com> wrote:
> 
>> Alan Cox wrote:
>>> Hopefully there is a better long term solution but for now lets favour
>>> reliability.
>> I'm getting a lot of reports on pata_ali w/ misc ATAPI commands too.  Do
>> you know whether it's a controller problem or drive one?  All the
>> reports I got are laptops and I can't really ask them to disassemble
>> their laptops.  :-)
> 
> ALi is one that most definitely appears to be controller related. Thats
> why I sent Jeff a patch to use DMA for 2K+ transfers only. Some ALi also
> required the patch to set the xfer lengths.
> 
> Its only some revs/combinations annoyingly - a lot of them (including the
> ones I have direct access too) just work.

Does READ_CD work fine via DMA?  2K+ filtering filters most if not all
misc commands so usually only sector (2K) aligned READ and WRITEs are
done via DMA.  Interesting exceptions are READ_CD[_MSF] and
READ/WRITE_BUFFER which usually exceed 2K but aren't aligned to 2K.  I
guess it's about time to write a test case program which issues a bunch
of problematic commands and see which works.

Thanks.

-- 
tejun