Re: [PATCHv3 10/19] iommu/tegra: smmu: Get "nvidia,swgroups" from DT

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Stephen Warren <swarren@xxxxxxxxxxxxx> wrote @ Fri, 1 Nov 2013 17:54:37 +0100:

> On 10/31/2013 02:17 AM, Hiroshi Doyu wrote:
> > Stephen Warren <swarren@xxxxxxxxxxxxx> wrote @ Wed, 30 Oct 2013 23:33:32 +0100:
> ...
> > Right.
> > "memory client ID" is used to find out MC_SMMU_<swgroup>_ASID_0
> > register. This register is used to associate <swgroup> to address
> > space(AS). <swgroup> == H/W. <swgroup> can be attached to any AS.
> > 
> >> Is "swgroup" simply another name for "memory client ID"? If so, it'd
> >> be good to use just one term consistently.
> > 
> > I used the name "memory client ID" because this ID can be used to find
> > out HOTRESET bit in MC_CLIENT_HOTRESET_*_0 registers in addition to
> > find the MC_SMMU_<swgroup>_ASID_0 offset. But maybe it's easy to use
> > the consistent name as "swgroup". If laster HOTRESET wants automatic
> > calculation they could borrow/redefine the same ID list, just
> > replacing the prefix. What do you think?
> > 
> >> Assuming "swgroup" is "memory client ID",
> > 
> > Yes
> 
> I took a look at the TRM, and it does look like there's a distinction
> between client IDs and swgroups. The basic idea is that each swgroup
> encompasses n (n >= 1) memory client IDs. So, we do have to use both terms.

Well, I considred that memory-client's' ~= 'a' swgroup, and the term
"swgroup" isn't used in HOTREST, where actually each bit represents
a "swgroup".

> However, the bits in the HOTRESET register appear mostly align with
> swgroup IDs rather client IDs, so I think some of your explanation above
> is innaccurate.
> 
> I do want to point out that the HOTRESET bits don't 100% match the
> swgroup IDs though, so the driver needs to be careful, and perhaps
> contain some kind of mapping table between the two numbering spaces. In
> particular, on Tegra114, swgroups and ASID registers appear in order
> PPCS, <gap>, SATA, whereas there's no gap between the HOTRESET bits for
> PPCS and SATA, assuming the TRM is correct.

In our downstream, basically I provided to two conversion tables, one
for "MC_SMMU_<swgroup ID>_ASID_0" and the other for "HOTRESET"
bit. That table converts ID to them respectively. I think that this is
acceptable.
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