Tejun Heo wrote:

Hello, Mark.

Mark Lord wrote:

quoted

Tejun, I've added PMP to sata_mv, and am now trying to get it
to work with a Marvell PM attached.

And the behaviour I see is very bizarre.

After hard+soft resets, the PM signature is found,
and libata interrogates the PM registers.

It successfully reads register 0, and then register 1.
But all subsequent registers read out (incorrectly) as zeros.

Hmmm...

quoted

I've traced the taskfiles in/out, and it all looks proper
except for the actual data coming back from the PM.

After some experimentation, I found that all of the PM registers
were readable, if I simple inserted a  sata_pmp_read(link, 0, &junk)
in front of each issue of sata_pmp_read(link, reg, &r_val).

Hmmmmmmm...

quoted

Then the PM is recognized and all, but fails port enumerations
probably due to either my hack or the same original bug (whatever that is?)

I'm confused.

That makes two of us.

quoted

The PM itself works fine here on sata_sil24 and AHCI(jmicron),

..

Well, last night I found someone else to try the code
with a 0x1095:0x3726 (vendor/device?) Port-Multiplier.
It *appears* to work fine with sata_mv, unlike the Marvell one.
Hopefully the nice folks at Marvell will take a look (I've emailed them)
and report back with some useful information eventually.

No but I had my fair share of problems doing PMP support for both sil24
and ahci.  Any chance you can get access to a bus analyzer?  I had a
very weird problem w/ ahci PMP support which I don't think I could fix
if I didn't have access to a bus analyzer at the time.  (I don't
remember details now tho.)

..

I figure they must have a few of those kicking around at Marvell..

Cheers
-- 
Mark Lord
Real-Time Remedies Inc.
mlord@pobox.com