[cc'ing Alan, thanks for the information on the other message]

Tobias Müller wrote:
> Tejun Heo schrieb:
>> I don't know very well about CF but does it even fill UDMA/33?  What
>> does 'dd if=/dev/sdc of=/dev/null bs=1M count=16 iflag=direct' say?  You
>> can increase count for more reliable result.
> 
> 16+0 Datensätze ein
> 16+0 Datensätze aus
> 16777216 Bytes (17 MB) kopiert, 0,561688 s, 29,9 MB/s

Hmmm... yeah, it almost fills UDMA/33.  I wonder whether it would go higher.

> And hdparm -I /dev/sdc says it should be compatible to udma5.
> 
>         DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2 udma3 udma4

Please apply the attached patch and specify libata.force_cbl=80 as
kernel boot parameter.  If you load libata from initrd or after boot you
need to pass 'force_cbl=80' as module parameter.  How you do it depends
on your distro.

Thanks.

-- 
tejun