Hello, Rusty. Rusty Conover wrote: > I have some interesting results. > > I had a pair of Seagate 250 GB SATA disks (models below) and tried those > out rather then the WD's. At the 1.5 gbps rather they appear to work > just fine both being on the same PMP, at 3.0 gbps they timeout just like > the other disks did. Possibly, the code isn't detecting the max rate of > the disks correctly since these drives only do 1.5 and it attempted to > do 3.0 gbps?
Hardware PHY layer is fully responsible of 1.5/3.0 negotiation. The driver can limit the maximum it can go but doesn't have much say in the actual negotiation. Unfortunately, some SATA PHY combinations have problems at 3.0bps. I saw quite a few weird cases. e.g. marvell PMP can't detect older Seagate drives on 3Gbps and can't talk to a first gen Maxtor even at 1.5. I'm still not quite sure how to solve this. Once detected, libata EH will do the right thing and speed down to 1.5 after a few transmission errors but it's a bit trickier before detection. It's probably not worth driving fan-out ports at 3.0Ghz in the first place so maybe limiting PMP fan-out ports to 1.5 by default can alleviate most situations. Oh well, users won't be happy tho. > Have you found that drives can be picky if they will work or not with > PMP ports? As I said above, yeap. Not only PMPs some host PHYs do that too. > I'll be trying to get a bunch of different drives to replace the ones > that don't work with PMP. Yeah, that will be the easiest way out for the moment. Thanks. -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
