linux-kernel - Re: [PATCH 1/2] soc: qcom: rpmhpd: Use corner in power

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Date:   Wed, 7 Jul 2021 23:35:52 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] soc: qcom: rpmhpd: Use corner in power_off

On Wed 07 Jul 19:21 CDT 2021, Stephen Boyd wrote:

> Quoting Bjorn Andersson (2021-07-02 17:54:15)
> > rpmhpd_aggregate_corner() takes a corner as parameter, but in
> > rpmhpd_power_off() the code requests the level of the first corner
> > instead.
> >
> > In all (known) current cases the first corner has level 0, so this
> > change should be a nop, but in case that there's a power domain with a
> > non-zero lowest level this makes sure that rpmhpd_power_off() actually
> > requests the lowest level - which is the closest to "power off" we can
> > get.
> >
> > While touching the code, also skip the unnecessary zero-initialization
> > of "ret".
> >
> > Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > ---
> 
> I think this is why qcom folks talk about "virtual corner" and "physical
> corner" because there's the one in command DB and the one in hardware.

I think the driver uses "level" and "corner" to denote the two different
number spaces, so I think we're good...now that we after this patch
don't pass a "level" as "corner" during power_off ;)

> Maybe we should change rpmhpd_aggregate_corner() to call the argument
> 'vcorner'?

So "virtual corner" is "corner" and "physical corner" is level? I.e. 256
is a "physical corner"?

Or did you get the suggestion backwards?

> Unfortunately we can't really build a type system here to
> make this problem easy to catch with a mismatched type, unless there's
> some sort of typedef trick we can play?
> 

s/i/corner/ in rpmhpd_set_performance_state() would further enforce the
naming scheme used and reduce the risk for future confusion.

But we did just squash the final bug... ;)

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

Thanks,
Bjorn