linux-kernel - Re: [RFC/PATCH 0/5] DVFS in the OPP core

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Date:   Thu, 07 Feb 2019 11:47:34 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-spi@...r.kernel.org,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [RFC/PATCH 0/5] DVFS in the OPP core

Quoting Rajendra Nayak (2019-02-06 22:57:12)
> 
> > 3) How do we handle devices that already have power-domains specified in
> > DT? The opp binding for required-opps doesn't let us specify the power
> > domain to target, instead it assumes that whatever power domain is
> > attached to a device is the one that OPP needs to use to change the
> > genpd performance state. Do we need a
> > dev_pm_opp_set_required_opps_name() or something to be explicit about
> > this? Can we have some way for the power domain that required-opps
> > correspond to be expressed in the OPP tables themselves?
> 
> I was converting a few more drivers to use the proposed approach in this
> RFC, in order to identify all outstanding issues we need to deal with,
> and specifically for UFS, I end up with this exact scenario where UFS already
> has an existing power domain (gdsc) and I need to add another one (rpmhpd) for
> setting the performance state.
> 
> If I use dev_pm_opp_of_add_table() to add the opp table from DT, the opp
> layer assumes its the same device on which it can do a dev_pm_genpd_set_performance_state()
> with, however the device that's actually associated with the pm_domain when we
> have multiple power domains is infact the one (dummy) that we create when
> the driver makes a call to dev_pm_domain_attach_by_name/id().
> 
> Any thoughts on whats a good way to handle this?
> 

Ulf mentioned that we can use dev_pm_opp_set_genpd_virt_dev() for this.
Does that API work here?