Thanks Viresh for your explanation. BR, Andy > -----Original Message----- > From: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > Sent: 2019年5月10日 18:12 > To: Andy Tang <andy.tang@xxxxxxx> > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>; Shawn Guo > <shawnguo@xxxxxxxxxx>; Leo Li <leoyang.li@xxxxxxx>; robh+dt@xxxxxxxxxx; > mark.rutland@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > linux-pm@xxxxxxxxxxxxxxx; rui.zhang@xxxxxxxxx; edubezval@xxxxxxxxx > Subject: Re: [EXT] Re: [PATCH v6] arm64: dts: ls1088a: add one more thermal > zone node > > Caution: EXT Email > > On 10-05-19, 08:47, Andy Tang wrote: > > + Viresh for help. > > > > > -----Original Message----- > > > From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> > > > Sent: 2019年5月10日 15:17 > > > To: Andy Tang <andy.tang@xxxxxxx>; Shawn Guo > <shawnguo@xxxxxxxxxx> > > > Cc: Leo Li <leoyang.li@xxxxxxx>; robh+dt@xxxxxxxxxx; > > > mark.rutland@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > > > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > linux-pm@xxxxxxxxxxxxxxx; rui.zhang@xxxxxxxxx; edubezval@xxxxxxxxx > > > Subject: Re: [EXT] Re: [PATCH v6] arm64: dts: ls1088a: add one more > > > thermal zone node > > > > > > Caution: EXT Email > > > > > > On 10/05/2019 05:40, Andy Tang wrote: > > > >> -----Original Message----- > > > >> From: Shawn Guo <shawnguo@xxxxxxxxxx> > > > >> Sent: 2019年5月10日 11:14 > > > >> To: Andy Tang <andy.tang@xxxxxxx> > > > >> Cc: Leo Li <leoyang.li@xxxxxxx>; robh+dt@xxxxxxxxxx; > > > >> mark.rutland@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > > > >> devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > >> linux-pm@xxxxxxxxxxxxxxx; daniel.lezcano@xxxxxxxxxx; > > > >> rui.zhang@xxxxxxxxx; edubezval@xxxxxxxxx > > > >> Subject: [EXT] Re: [PATCH v6] arm64: dts: ls1088a: add one more > > > >> thermal zone node > > > >> > > > >> Caution: EXT Email > > > >> > > > >> On Tue, Apr 23, 2019 at 10:25:07AM +0800, Yuantian Tang wrote: > > > >>> Ls1088a has 2 thermal sensors, core cluster and SoC platform. > > > >>> Core cluster sensor is used to monitor the temperature of core > > > >>> and SoC platform is for platform. The current dts only support the first > sensor. > > > >>> This patch adds the second sensor node to dts to enable it. > > > >>> > > > >>> Signed-off-by: Yuantian Tang <andy.tang@xxxxxxx> > > > >>> --- > > > >>> v6: > > > >>> - add cooling device map to cpu0-7 in platform node. > > > > I like to explain a little. I think it makes sense that multiple > > > > thermal zone > > > map to same cooling device. > > > > In this way, no matter which thermal zone raises a temp alarm, it > > > > can call > > > cooling device to chill out. > > > > I also asked cpufreq maintainer about the cooling map issue, he > > > > think it > > > would be fine. > > Yes, you asked me and I said it should be okay. > > > > > I have tested and no issue found. > > > > > > > > Daniel, what's your thought? > > > > > > If there are multiple thermal zones, they will be managed by > > > different instances of a thermal governor. Each instances will act > > > on the shared cooling device and will collide in their decisions: > > > > > > - If the sensors are closed, their behavior will be similar > > > regarding the temperature. The governors may take the same decision > > > for the cooling device. But in such case having just one thermal zone > managed is enough. > > > > > > - If the sensors are not closed, their behavior will be different > > > regarding the temperature. The governors will take different > > > decision regarding the cooling device (one will decrease the freq, other > will increase the freq). > > > > > > As the thermal governors are not able to manage several thermal > > > zones and there is one cooling device (the cpu cooling device), this > > > setup won't work as expected IMO. > > > > > > The setup making sense is having a thermal zone per 'cluster' and a > > > cooling device per 'cluster'. That means the platform has one clock line > per 'cluster'. > > > The thermal management happens in a self-contained thermal zone (one > > > cooling device - one governor - one thermal zone). > > > > > > In the case of HMP, other combinations are possible to be optimal. > > But not sure how I missed the obvious, though I do remember thinking about > this. > > So the problem is that the cpu_cooling driver will get requests in parallel to > set different max frequencies and the last call will always win and may result > in undesired outcome. > > Sorry about creating the confusion. > > -- > viresh
