2007-06-28 17:19:17

by Roy Franz (HPE)

Subject: Unable to change sata NCQ depth due to readonly /sys/block/sdc/device/queue_depth file

Hi,

I am unable to change the NCQ settings for a sata drive that
supports it - NCQ is always on. This is due to the sysfs queue_depth
file being read-only. This is on
vanilla 2.6.21.5 running with Debian Etch. (Several earlier versions
of the kernel
had this same issue.) The drive (WD Raptor) is hooked up to a Nvidia
sata controller.

amd64:/# ls -al /sys/block/sdc/device/queue_depth
-r--r--r-- 1 root root 4096 2007-06-28 10:04 /sys/block/sdc/device/queue_depth
amd64:/# cat /sys/block/sdc/device/queue_depth
31
amd64:/#

I searched but did not find any helpful information on this. Forcing
a change by changing permissions on the file did not work.

Thanks,
Roy

2007-06-28 23:21:38

by Robert Hancock

Subject: Re: Unable to change sata NCQ depth due to readonly /sys/block/sdc/device/queue_depth file

Roy Franz wrote:
> Hi,
>
> I am unable to change the NCQ settings for a sata drive that
> supports it - NCQ is always on. This is due to the sysfs queue_depth
> file being read-only. This is on
> vanilla 2.6.21.5 running with Debian Etch. (Several earlier versions
> of the kernel
> had this same issue.) The drive (WD Raptor) is hooked up to a Nvidia
> sata controller.
>
> amd64:/# ls -al /sys/block/sdc/device/queue_depth
> -r--r--r-- 1 root root 4096 2007-06-28 10:04
> /sys/block/sdc/device/queue_depth
> amd64:/# cat /sys/block/sdc/device/queue_depth
> 31
> amd64:/#
>
> I searched but did not find any helpful information on this. Forcing
> a change by changing permissions on the file did not work.

Looks like sata_nv is missing the change_queue_depth function in the
SCSI host template, resulting in this file showing as read-only. I'll
cook up a patch when I get a chance.

--
Robert Hancock Saskatoon, SK, Canada
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Home Page: http://www.roberthancock.com/