Re: Resets on sil3124 & sil3726 PMP

[Tejun Heo <htejun@gmail.com>]

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