[clue-tech] 2.6.18 (CentOS 5.x) kernel initialize IDE drives in UDMA2 mode?

[Jim Ockers]

Hi CLUEbies,

For various very important reasons we have to run our Linux systems with 
CentOS 5.x with all IDE drives in UDMA2 (or slower) mode.  Of course the 
2.6 kernel IDE device driver, the chipset on our motherboard, and the 
drives, all support UDMA5 or UDMA6 and autonegotiate the fastest speed 
they support when the driver initializes the drive.

When we try to use hdparm to change it back to UDMA2 (hdparm -d 1 -X 
udma2 /dev/hdX) we occasionally get errors.  We think there are some 
timing issues in hdparm and possibly the kernel, and probably the IDE 
drive firmware too.  We have a dizzying variety of chipsets/motherboards 
and hard drives and depending on the combination of those (and whether 
or not we have a 40 pin or 80 pin IDE cable) we occasionally get errors 
like this:

hda: set_drive_speed_status: status=0x58 { DriveReady SeekComplete 
DataRequest }
ide: failed opcode was: unknown
ide0: Drive 0 didn't accept speed setting. Oh, well.
hda: CHECK for good STATUS

AND THEN DMA IS DISABLED WHICH IS REALLY BAD FOR OUR SYSTEMS.  Please 
don't suggest that the drives are bad because we have exhaustive drive 
tests and all drives which fail this way pass all the tests.

We also tried booting the kernel with ide=nodma and then one of the 
first init scripts turns on UDMA2.  This makes the above error happen a 
lot less often (maybe 95% less) but it still happens repeatably from 
time to time.

I think that trying to set the DMA mode after initialization is maybe 
not a good idea.  If we could make the 2.6.18 IDE driver start up in 
UDMA2 mode instead of the default fastest mode that might sidestep the 
problem altogether.  Does anyone in CLUEland know what is the fastest 
way to do this?  By the way the IDE driver in the CentOS 5.x kernel 
(2.6.18) is not a module.  My googling has not turned up anything and 
there is no kernel command line option for the IDE driver that does this.

Thanks,
Jim

-- 
Jim Ockers, P.Eng. (ockers at ockers.net)
Contact info: http://www.ockers.ca/pason.html


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://cluedenver.org/pipermail/clue-tech/attachments/20090902/4a76481a/attachment.html