linux-kernel - Re: [PATCH 2/2] arm64: dts: imx8mm: Assign highest opp as suspend opp

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Date:   Mon, 8 Jul 2019 13:55:11 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Anson Huang <anson.huang@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Jacky Bai <ping.bai@....com>,
        Daniel Baluta <daniel.baluta@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        Abel Vesa <abel.vesa@....com>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.com>,
        "ccaione@...libre.com" <ccaione@...libre.com>,
        "angus@...ea.ca" <angus@...ea.ca>,
        "agx@...xcpu.org" <agx@...xcpu.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 2/2] arm64: dts: imx8mm: Assign highest opp as suspend opp

On 04-07-19, 07:49, Leonard Crestez wrote:
> On 7/4/2019 9:23 AM, Anson.Huang@....com wrote:
> > From: Anson Huang <Anson.Huang@....com>
> > 
> > Assign highest OPP as suspend OPP to reduce suspend/resume
> > latency on i.MX8MM.
> > 
> > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > ---
> >   arch/arm64/boot/dts/freescale/imx8mm.dtsi | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > index b11fc5e..3a62407 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > @@ -136,6 +136,7 @@
> >   			opp-microvolt = <1000000>;
> >   			opp-supported-hw = <0x8>, <0x3>;
> >   			clock-latency-ns = <150000>;
> > +			opp-suspend;
> >   		};
> >   	};
> 
> What if the highest OPP is unavailable due to speed grading?

What does this exactly mean ? How is the OPP made unavailable in your
case ?

What will dev_pm_opp_get_suspend_opp_freq() return in this case ?

> Ideally we 
> should find a way to suspend at the highest *supported* OPP.
> 
> Maybe the opp-suspend marking could be assigned from imx-cpufreq-dt 
> driver code?

Sorry for jumping in late, the latest patch from Anson drew my
attention to this topic :)

-- 
viresh