Re: What's needed for PMP support?

[Mark Lord <liml@rtr.ca>]

Tejun Heo wrote:
> Mark Lord wrote:
>> Mark Lord wrote:
>>> Tejun Heo wrote:
>>>>> The following things are needed for a LLD to support PMP.
>>>> ..
>>>>> I think that's about it.  Feel free to ask if something isn't clear.
>>> ..
>>>
>>> I think we need better semantics around sata_scr_{read,write}(),
>>> or more specifically
>>> These need to be moved into ata_port_operations
>>> so that LLDs can wrap them to properly manage
>>> the host controller's global link->pmp value.
>> ..
>>
>> Heck, if .dev_select() took a *device* instead of a *port*
>> as it's parameter, then I could probably manage it fine in there.
> 
> Heh... I never thought a PMP aware controller would use TF SRST, so what
> you want to do is set pmp value in the register and calling
> ata_std_softreset(), right?  I think the correct thing to do is to
> separate out SRST sequence proper from ata_std_softreset() into, say,
> ata_sff_SRST() and build custom softreset around it.  After all, the
> problem here is the reset sequence not the SCR access.
..

Actually, I believe the problem *is* the (pmp) SCR access.
The same issue will return again when trying to support hotplug, for example.

Any SCR access will steal the active pmp on such hosts.

I think we really do need to snoop those, somehow.

Cheers