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Date:   Wed, 12 Aug 2020 10:53:44 +0200
From:   Ulf Hansson <>
To:     Stephan Gerhold <>
Cc:     Viresh Kumar <>,
        "Rafael J. Wysocki" <>,
        Kevin Hilman <>, Nishanth Menon <>,
        Stephen Boyd <>,
        Linux PM <>,
        Linux Kernel Mailing List <>,
        Niklas Cassel <>
Subject: Re: [RFC PATCH 0/3] opp: required_opps: Power on genpd, scale down in
 reverse order

On Thu, 30 Jul 2020 at 10:02, Stephan Gerhold <> wrote:
> I'm trying to get CPR (Core Power Reduction, AVS) working for MSM8916 on mainline.
> Shortly said there are two power domains that must be scaled with the CPU OPP table:
>   - (VDD)MX
>   - CPR
> My idea for this was to add both as "required-opps" to the CPR OPP table
> and let the OPP core take care of all the scaling.
> There are two remaining problems that need to be addressed for that to work:
>   1. The power domains should be scaled down in reverse order
>      (MX, CPR when scaling up, CPR, MX when scaling down).
>   2. Something has to enable the virtual genpd devices to make the rpmpd driver
>      actually respect the performance states we vote for.
> Both issues were briefly discussed before (see links in the patches),
> but I think we did not agree on an exact solution yet. After some consideration,
> I thought it would be best to address these directly in the OPP core.
> However, note that this patch is RFC because it is just supposed to initiate
> discussion if alternative solutions would be better. :)

Ramping up since the holidays, so I might overlook something - but I
think your suggestion solution makes perfect sense to me.

> Stephan Gerhold (3):
>   opp: Reduce code duplication in _set_required_opps()
>   opp: Set required OPPs in reverse order when scaling down
>   opp: Power on (virtual) power domains managed by the OPP core
>  drivers/opp/core.c | 115 ++++++++++++++++++++++++++++++++++++---------
>  drivers/opp/opp.h  |   1 +
>  2 files changed, 93 insertions(+), 23 deletions(-)
> --
> 2.27.0

So, for the series:

Reviewed-by: Ulf Hansson <>

Kind regards

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