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From: Stephen Boyd <swboyd@chromium.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Rajendra Nayak <rnayak@codeaurora.org>,
	ulf.hansson@linaro.org, viresh.kumar@linaro.org,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	rojay@codeaurora.org, stephan@gerhold.net
Subject: Re: [PATCH v4 2/2] arm64: dts: sc7180: Add required-opps for i2c
Date: Fri, 16 Jul 2021 23:49:16 +0200	[thread overview]
Message-ID: <CAE-0n50qx80cMFPJ1x9rc+EMR1L+j2CUMyDjWAbnE9mPHjf-TQ@mail.gmail.com> (raw)
In-Reply-To: <YPHxfHPC/faq/y+J@yoga>

Quoting Bjorn Andersson (2021-07-16 13:52:12)
> On Fri 16 Jul 15:21 CDT 2021, Stephen Boyd wrote:
>
> > Quoting Bjorn Andersson (2021-07-16 13:18:56)
> > > On Fri 16 Jul 05:00 CDT 2021, Rajendra Nayak wrote:
> > >
> > > > qup-i2c devices on sc7180 are clocked with a fixed clock (19.2 MHz)
> > > > Though qup-i2c does not support DVFS, it still needs to vote for a
> > > > performance state on 'CX' to satisfy the 19.2 Mhz clock frequency
> > > > requirement.
> > > >
> > >
> > > Sounds good, but...
> > >
> > > > Use 'required-opps' to pass this information from
> > > > device tree, and also add the power-domains property to specify
> > > > the CX power-domain.
> > > >
> > >
> > > ..is the required-opps really needed with my rpmhpd patch in place?
> > >
> >
> > Yes? Because rpmhpd_opp_low_svs is not the lowest performance state for
> > CX.
>
> On e.g. sm8250 the first available non-zero corner presented in cmd-db
> is low_svs.

Indeed. On sc7180 it's not the first non-zero corner. I suppose
retention for CX isn't actually used when the SoC is awake so your
rpmhpd patch is putting in a vote for something that doesn't do anything
at runtime for CX? I imagine that rpmh only sets the aggregate corner to
retention when the whole SoC is suspended/sleeping, otherwise things
wouldn't go very well. Similarly, min_svs may be VDD minimization? If
so, those first two states are basically states that shouldn't be used
at runtime, almost like sleep states.

>
> And if this (which?) clock requires a higher corner than the lowest
> possible in order to tick at this "lowest" frequency, I'm certainly
> interested in some more details.
>

  reply	other threads:[~2021-07-16 21:49 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-16 10:00 [PATCH v4 0/2] PM / Domains: Add support for 'required-opps' to set default perf state Rajendra Nayak
2021-07-16 10:00 ` [PATCH v4 1/2] " Rajendra Nayak
2021-07-16 20:19   ` Stephen Boyd
2021-07-19 11:50     ` Rajendra Nayak
2021-07-16 10:00 ` [PATCH v4 2/2] arm64: dts: sc7180: Add required-opps for i2c Rajendra Nayak
2021-07-16 19:39   ` Stephen Boyd
2021-07-16 20:18   ` Bjorn Andersson
2021-07-16 20:21     ` Stephen Boyd
2021-07-16 20:52       ` Bjorn Andersson
2021-07-16 21:49         ` Stephen Boyd [this message]
2021-07-16 21:59           ` Bjorn Andersson
2021-07-19  9:37             ` Rajendra Nayak
2021-07-19 19:19               ` Bjorn Andersson
2021-07-20  4:29                 ` Rajendra Nayak
2021-07-25 17:01                   ` Bjorn Andersson
2021-07-27  7:35                     ` Rajendra Nayak
2021-07-28  3:46                       ` Bjorn Andersson
2021-07-28 14:01                         ` Dmitry Baryshkov
2021-07-28 18:47                           ` Bjorn Andersson

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