Messages in this thread | | | Date | Tue, 11 Dec 2018 09:49:10 +0000 | From | Quentin Perret <> | Subject | Re: [RFC PATCH] PM / OPP: Always expose one supply in debugfs |
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On Tuesday 11 Dec 2018 at 14:55:49 (+0530), Viresh Kumar wrote: > On 10-12-18, 11:54, Quentin Perret wrote: > > On Monday 10 Dec 2018 at 11:32:47 (+0000), Quentin Perret wrote: > > > On some platforms, the opp_table->regulator_count field is kept at zero > > > even though opp->supplies is always allocated. However, the loop used to > > > display the supplies in the debugfs doesn't deal correctly with this, > > > which results in the supplies not being displayed in debugfs on those > > > platforms. > > > > > > Fix this by making sure to always display at least once supply in > > > debugfs. > > > > > > Signed-off-by: Quentin Perret <quentin.perret@arm.com> > > > > > > --- > > > > > > This has been observed on Juno r2 which uses SCPI and Hikey960 which > > > uses DT. I am not particularly familiar with that part of the code, so > > > I'm not sure if this is even remotely correct (hence the RFC tag). > > > > > > I first thought setting opp_table->regulator_count to 1 would be the > > > right fix but that causes other issues. This fix seems to work OK on > > > Juno and Hikey960, at least. > > > > > > Feedback is welcome :-) > > > > Hmm, so I just figured what I'm doing here is basically reverting: > > > > 1fae788ed640 ("PM / OPP: Don't create debugfs "supply-0" directory unnecessarily") > > > > Should I send a proper revert instead of this patch ? It _is_ handy to > > read voltage numbers when available. > > First of all I am really happy that someone apart from me is using this debug > interface :)
:-)
My current use case is to compute the 'dynamic-power-coefficient' thing for IPA. With P=CV^2f, I can measure P and get f easily, but V is a bit trickier (as of now at least). PM_OPP has the information I need, so it'd be handy to expose it somewhere.
> At least that patch was correct and if we have to fix something, it should be > fixed somewhere else.
Understood.
> I tried to reproduce the issue on hikey and straight away understood why it is > behaving that way. There is no "cpu-supply" property defined for the CPUs.
Ah, right. The opp-microvolt binding is specified however, so I guess we could expose that too ...
> I looked at juno driver and couldn't see any references to voltage there. Are > you trying to add that support ?
So, on Juno we do get voltage numbers from firmware, and those get registered properly in PM_OPP, exactly like for Hikey960. So it's probably the same problem in both cases.
FWIW, this is what I get on juno with my 'fix' applied:
$ cat /sys/kernel/debug/opp/cpu0/*/supply-0/u_volt_target 820000 850000 900000 950000 1000000
> Anyway, this should still be fixed irrespective of the "cpu-supply" property. > The other fix you mentioned about setting opp_table->regulator_count to 1 is > actually the right thing to do but the fix may require changes at multiple > places. I can help writing a patch for that if you want, else I am open to you > giving it a shot :)
You'll definitely know the code better than me so if you have a patch in mind, please don't hesitate. I'll be happy to test it on my two boards here :-)
Thanks, Quentin
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