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Date: Sun, 24 May 2020 00:50:18 +0000 From: Anson Huang <anson.huang@....com> To: Daniel Lezcano <daniel.lezcano@...aro.org>, "rui.zhang@...el.com" <rui.zhang@...el.com>, "amit.kucheria@...durent.com" <amit.kucheria@...durent.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>, "linux-pm@...r.kernel.org" <linux-pm@...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> CC: dl-linux-imx <linux-imx@....com> Subject: RE: [PATCH] thermal: imx8mm: Add get_trend ops Hi, Daniel > Subject: Re: [PATCH] thermal: imx8mm: Add get_trend ops > > On 23/05/2020 02:35, Anson Huang wrote: > > Hi, Daniel > > > > > >> Subject: Re: [PATCH] thermal: imx8mm: Add get_trend ops > >> > >> On 13/05/2020 04:58, Anson Huang wrote: > >>> Add get_trend ops for i.MX8MM thermal to apply fast cooling > >>> mechanism, when temperature exceeds passive trip point, the highest > >>> cooling action will be applied, and when temperature drops to lower > >>> than the margin below passive trip point, the lowest cooling action > >>> will be applied. > >> > >> You are not describing what is the goal of this change. > > > > The goal of this change is to make sure whenever temperature exceeds > > passive trip point, the highest cooling action will be applied > > immediately, e.g., if there are many cpufreq OPP, the default cooling > > will be step by step, it will take some more rounds to make cpufreq drop to > lowest OPP, while on i.MX, we expect the cpufreq drop to lowest OPP > immediately. > > Whatever the slope of the temperature increase? Yes. > > >> IIUC, the resulting change will be an on/off action. The thermal zone > >> is mitigated with the highest cooling effect, so the lowest OPP, then > >> the temperature trend is stable until it goes below the trip - margin > >> where the mitigation is stopped. > > > > Yes, your understanding is correctly, once the temperature exceeds > > passive trip point, the highest cooling action will be applied > > immediately and then it will be stable there until temperature drop to > > trip - margin, then the cooling action will be cancelled, the margin is to avoid > the back and forth near the passive trip point. > > > >> > >> Except, I'm missing something, setting a trip point with a 10000 > >> hysteresis and a cooling map min/max set to the highest opp will result on > the same. > > > > Yes setting cooling map min/max cooling state to highest OPP will make > > the highest cooling action applied immediately, and to have the > > function of cooling action being cancelled when temperature drops to > > trip - margin, I have to define another trip point, say passive trip > > point is 85000, and cooling map min/max set to highest OPP in passive > > trip point then add another trip point named "active" with 75000, and > without any cooling map in it, right? > > May be I misunderstood but only the change as below is needed. No need to > add a trip point, especially an 'active' trip which is a for an active cooling > device like a fan. > > diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi > b/arch/arm64/boot/dts/freescale/imx8mm.dtsi > index cc7152ecedd9..bea263bd06b4 100644 > --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi > +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi > @@ -231,10 +231,10 @@ cooling-maps { > map0 { > trip = <&cpu_alert0>; > cooling-device = > - <&A53_0 THERMAL_NO_LIMIT > THERMAL_NO_LIMIT>, > - <&A53_1 THERMAL_NO_LIMIT > THERMAL_NO_LIMIT>, > - <&A53_2 THERMAL_NO_LIMIT > THERMAL_NO_LIMIT>, > - <&A53_3 THERMAL_NO_LIMIT > THERMAL_NO_LIMIT>; > + <&A53_0 2 2>, > + <&A53_1 2 2>, > + <&A53_2 2 2>, > + <&A53_3 2 2> > }; > }; > }; > > Thanks, I will have a try to see if it meets our expectation. Anson
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