linux-kernel - Re: [PATCH v3] soc: qcom: rpmhpd: Make power

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Date:   Fri, 15 Oct 2021 17:17:25 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] soc: qcom: rpmhpd: Make power_on actually enable the domain

Quoting Bjorn Andersson (2021-10-04 20:37:32)
> The general expectation is that powering on a power-domain should make
> the power domain deliver some power, and if a specific performance state
> is needed further requests has to be made.
>
> But in contrast with other power-domain implementations (e.g. rpmpd) the
> RPMh does not have an interface to enable the power, so the driver has
> to vote for a particular corner (performance level) in rpmh_power_on().
>
> But the corner is never initialized, so a typical request to simply
> enable the power domain would not actually turn on the hardware. Further
> more, when no more clients vote for a performance state (i.e. the
> aggregated vote is 0) the power domain would be turned off.
>
> Fix both of these issues by always voting for a corner with non-zero
> value, when the power domain is enabled.
>
> The tracking of the lowest non-zero corner is performed to handle the
> corner case if there's ever a domain with a non-zero lowest corner, in
> which case both rpmh_power_on() and rpmh_rpmhpd_set_performance_state()
> would be allowed to use this lowest corner.
>
> Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---

Looks ok to me.

Reviewed-by: Stephen Boyd <swboyd@...omium.org>