Re: What's needed for PMP support?

[Mark Lord <mlord@pobox.com>]

Tejun Heo wrote:
> Hello, Mark.
> 
> Mark Lord wrote:
>> 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...
> 
>> 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...
> 
>> 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.
> 
>> 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