On Thu, Oct 04, 2018 at 10:18:22AM -0500, Rob Herring wrote:

On Thu, Oct 4, 2018 at 3:36 AM Viresh Kumar [off-list ref] wrote:

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On 25-09-18, 14:43, Rob Herring wrote:

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On Tue, Sep 25, 2018 at 5:25 AM Rajendra Nayak [off-list ref] wrote:

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Hi Rob,

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+   rpmhpd_opp_table: opp-table {
+           compatible = "operating-points-v2-qcom-level";
+
+           rpmhpd_opp_ret: opp1 {
+                   qcom,level = <RPMH_REGULATOR_LEVEL_RETENTION>;
+           };

I don't see the point in using the OPP binding here when you aren't
using *any* of the properties from it.

Yeah, that's the case for now. But there are cases (as Stephen
mentioned earlier [1]) where the voltage values (and maybe other
values like current, etc) would be known and filled in DT. And that's
why we all agreed to use OPP tables for PM domains as well, as these
are really "operating performance points" of these PM domains.

Rob, are you fine with these bindings then?

Okay, my only thought is whether we should just use 'reg' here, or do
we need 'level' for anything else and should make it common?

I am not quite sure I understood what you are suggesting here :(

You could use the  'reg' property instead of 'qcom,level'. Any reason
not to do that?

They can use any property which uniquely identifies the OPP nodes in
the table. Though I never thought we can use 'reg' property in such a
way. I always thought it must be related to registers somehow :)

That's almost certainly where the name originates from back in the
90s. I view 'reg' as how you identify or address a device. This can be
channels of something like an ADC.

It's perhaps a stretch for OPP nodes as they aren't really a device,
but if the levels are part of the h/w then perhaps reg is a good
match.

FWIW, I actually have a use case on qcom SoCs.

I'm working on reviving an old patch series from Stephen Boyd:
https://lkml.org/lkml/2015/9/18/833


Rajendra's Documentation/devicetree/bindings/opp/qcom-opp.txt currently has:

Required properties:
- qcom,level: On Qualcomm platforms an OPP node can describe a positive value
representing a corner/level that's communicated with a remote microprocessor
(usually called the RPM) which then translates it into a certain voltage on
a voltage rail


I'm planning on extending it with something like:

Optional properties:
-qcom,fuse-level: On Qualcomm platforms, not all corners/levels are real
corners/levels, i.e., not all corners/levels have a unique eFuse associated.
Usually more than one corner/level uses the same eFuse corner/level.


So for each OPP I would have:

opp1 {
	qcom,level = <foo>;
	qcom,fuse-level = <bar>;
}


Not sure if this changes your opinion about using reg,
but I thought that it was worth mentioning.


Kind regards,
Niklas