Re: What's needed for PMP support?

[Mark Lord <liml@rtr.ca>]

Mark Lord wrote:
> Tejun Heo wrote:
>> Mark Lord wrote:
>>>> 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.
>>
>> Can you elaborate a bit?
> ..
> 
> For example: a simple call to ata_link_online() is enough to mess it up.
> Say, from hotplug polling.
> 
> Or an SEMB access (if not now, then someday when we implement it)
> 
>>> Any SCR access will steal the active pmp on such hosts.
>>>
>>> I think we really do need to snoop those, somehow.
>>
>> Adding ->sata_pmp_scr_read/write should do but I wanna avoid that if
>> possible.
> ..
> 
> We already have .pmp_scr_{read,write} operations.
> If NULL, then default to the built-ins that are there now.
..

Mmm.. lost some lines there, try again:

We already have .scr_{read,write} operations, and
what I think we need are .pmp_scr_{read,write} in addition.
If NULL, then default to the built-ins that are there now.