Re: Kernel 2.6.30rc7 limits IDE to UDMA33

[Robert Hancock <hancockrwd@gmail.com>]

Alan Cox wrote:
>> I've relayed your reply to the pata_amd user on the forum. As for my
>> case with pata_via, until this is fixed, is there any way to force it
>> to use a higher UDMA? Is there a flag that can be passed in, for
> 
> In your case given the BIOS appears to be informing us you have a 40wire
> cable there isn't much that can be fixed
> 
>> example, in /sys somewhere? hdparm fails to set a higher UDMA and I
>> looked at sdparm but don't see anything in it to increase UDMA...
> 
> Tejun some time ago added stuff to override all of these things:
> 
> See Documentation/kernel-parameters.txt
> 
> 	libata.force=
> 
> which will let you override all sorts of autodetection for quirky boards

I wouldn't rule out the possibility of a bug. The code in pata_via looks 
a bit fishy, it reports a 40-wire cable if either the GTM data wasn't 
present or valid, or if it reports a mode of UDMA2 or less. In the 
former case it seems like ATA_CABLE_PATA_UNK would be the safer choice 
since we really don't know, and we should then use drive-side detection, 
rather than assuming a 40-wire cable by default..