Re: [PATCH] libata: blacklist NCQ on OCZ CORE 2 SSD

[Robert Hancock <hancockr@shaw.ca>]

Lubomír Bulej wrote:
> Hello,
> 
> after putting a 250G OCZ CORE v2 SSD into my notebook, I have to endure 
> several invocations of the ata EH before the kernel decides to disable 
> NCQ due too many errors. The drive reports NCQ of depth 1, which is 
> probably useless anyway.
> 
> The patchlet below saves me the waiting for the completion of several 
> ata EH invocations, but I'm not sure if this is the right solution. 
> Attached are two dmesg dumps, one with errors and the other with the 
> patchlet compiled in. Attached is also "hdparm -I" of the drive.

I suspect it's all we can really do. NCQ depth of 1 isn't entirely 
useless, as using NCQ commands still allows the drive to send/request 
data for an individual request out of order, which NCQ commands don't 
allow. However, in this case it would appear that the device is sending 
back a bogus all-zeros FIS to the controller which triggers error handling.

The "applying bridge limits" part is interesting, that would imply the 
device's identify data doesn't properly indicate it's actually a SATA 
device so the kernel assumes it's a PATA device behind a SATA bridge. I 
don't think it's related to the problem but it does suggest that whoever 
designed the SATA interface on that thing probably didn't do a ton of 
validation on it..