linux-kernel - Re: [PATCH v3] ARM: dts: mt8173: support arm64 cpuidle-dt

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Message-ID: <CAJ+MC=5oORYein5Z12Nb3vLDC4DLoyqUEyqZH95=LQWHBP23Sw@mail.gmail.com>
Date:	Tue, 2 Jun 2015 15:17:27 +0800
From:	Howard Chen <howard.chen@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	Matthias Brugger <matthias.bgg@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Eddie Huang <eddie.huang@...iatek.com>,
	"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>,
	"linux-mediatek@...ts.infradead.org" 
	<linux-mediatek@...ts.infradead.org>,
	"srv_heupstream@...iatek.com" <srv_heupstream@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Bobby Batacharia <Bobby.Batacharia@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH v3] ARM: dts: mt8173: support arm64 cpuidle-dt

On 29 May 2015 at 22:55, Lorenzo Pieralisi <lorenzo.pieralisi@....com> wrote:
> On Fri, May 29, 2015 at 08:01:46AM +0100, Howard Chen wrote:
>> This patch adds an idle-states node to describe the mt8173 idle states and
>> also adds references to the idle-states node in all CPU nodes.
>>
>> Signed-off-by: Howard Chen <howard.chen@...aro.org>
>> ---
> You should have added a list of incremental changes (v1->v2->v3) here
> otherwise there is no point in adding a patch version, we are not
> supposed to remember what you have changed.
>
OK.

>>  arch/arm64/boot/dts/mediatek/mt8173.dtsi | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
>> index 924fdb6..47e8d56 100644
>> --- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi
>> +++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
>> @@ -49,6 +49,8 @@
>>                       device_type = "cpu";
>>                       compatible = "arm,cortex-a53";
>>                       reg = <0x000>;
>> +                     enable-method = "psci";
>> +                     cpu-idle-states = <&CPU_SLEEP_0>;
>>               };
>>
>>               cpu1: cpu@1 {
>> @@ -56,6 +58,7 @@
>>                       compatible = "arm,cortex-a53";
>>                       reg = <0x001>;
>>                       enable-method = "psci";
>> +                     cpu-idle-states = <&CPU_SLEEP_0>;
>>               };
>>
>>               cpu2: cpu@100 {
>> @@ -63,6 +66,7 @@
>>                       compatible = "arm,cortex-a57";
>>                       reg = <0x100>;
>>                       enable-method = "psci";
>> +                     cpu-idle-states = <&CPU_SLEEP_0>;
>>               };
>>
>>               cpu3: cpu@101 {
>> @@ -70,6 +74,20 @@
>>                       compatible = "arm,cortex-a57";
>>                       reg = <0x101>;
>>                       enable-method = "psci";
>> +                     cpu-idle-states = <&CPU_SLEEP_0>;
>> +             };
>> +
>> +             idle-states {
>> +                     entry-method = "arm,psci";
>> +
>> +                     CPU_SLEEP_0: cpu-sleep-0 {
>> +                             compatible = "arm,idle-state";
>
> UltraNit: please move local-timer-stop here to keep the property ordering
> as in the bindings.
OK.

>
> More importantly, IIRC the idle state was not local-timer-stop in v2,

My original idea is to hand over to a general purpose timer when the
local timer stops, however, Danienl Lezcano naked this and points out cases
that it may misbehave. So I fall back to the generic approach which uses the
broadcast timer on the v3 patch.

> what changed in the interim ? v1->v2 the cluster idle state disappeared,

The cluster idle won't be available in the near future and possibly never will,
while the C1 state is ready and stable, so I split the C1 part out.

> now the local timer seems to stop when it was not before (and that is
> the same HW), I hope things are settled now.
>
> https://lkml.org/lkml/2015/4/7/76
>
>> +                             arm,psci-suspend-param = <0x0010000>;
>
> Move this property as last on the list, let's keep the generic
> properties first.
OK.

>
>> +                             entry-latency-us = <639>;
>> +                             exit-latency-us = <680>;
>> +                             min-residency-us = <1088>;
>> +                             local-timer-stop;
>> +                     };
>>               };
>>       };
>
> I guess there is no hope of seeing the cluster state restored (?).
>
> I would like some explanation regarding local-timer-stop change, apart
> from that you can add:
>
> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

Many thanks for your review and all the great comments.


Regards,
Howard
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