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

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Date:   Fri, 8 Feb 2019 10:09:26 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.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



On 2/8/2019 1:17 AM, Stephen Boyd wrote:
> 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?

Ah, yes, that should work, I hadn't noticed this API existed.

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