Re: What's needed for PMP support?

[Mark Lord <liml@rtr.ca>]

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.

I'll try it here first, though, and make sure it solves things.

Cheers