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Date: Wed, 5 Nov 2014 18:37:39 +0530
From: Chander Kashyap <k.chander@...sung.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc: Chander Kashyap <k.chander@...sung.com>,
Mark Rutland <Mark.Rutland@....com>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Catalin Marinas <Catalin.Marinas@....com>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
"rjw@...ysocki.net" <rjw@...ysocki.net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kgene.kim@...sung.com" <kgene.kim@...sung.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] arm64: dts: exynos7: add support for cpuidle core
power down
On Wed, Nov 5, 2014 at 4:42 PM, Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
> On Wed, Nov 05, 2014 at 10:15:36AM +0000, Chander Kashyap wrote:
>> Exynos7 has core power down state where cores can be powered off independently.
>> This patch adds support for this state.
>>
>> Entry latency for the core power down is calculated as follows:
>> 1. Time difference is measured between cpuidle entry and exit.
>> 2. WFI is skipped measuring the time.
>> 3. The time is averaged out for 100000 cpuidle transactions with varying load.
> - entry-latency-us
> Usage: Required
> "Definition: u32 value representing worst case latency in microseconds
> required to enter the idle state. ..."
>
> Is that an average value in your opinion ? I am being pedantic, I know,
> but we define bindings to be followed, not interpreted.
Sorry i missed the point.
The worst case value in a test set of 100000 cpuidle transactions is ~34us
I will update this and resend the patch.
>
> Thanks,
> Lorenzo
>
>> Exit latency and target residency are supplied as per HW team
>>
>> Signed-off-by: Chander Kashyap <k.chander@...sung.com>
>> ---
>> This patch has following dependencies:
>> - [PATCH v5 0/8] arch: arm64: Enable support for Samsung Exynos7 SoC
>> http://www.spinics.net/lists/linux-samsung-soc/msg37047.html
>> Changes in v2:
>> - Moved the cpu-idle-state property after reg property
>> - removed the status property.
>>
>> Changes in v3:
>> - Added the Entry latency calculation in commit message.
>>
>> arch/arm64/boot/dts/exynos/exynos7.dtsi | 17 +++++++++++++++++
>> 1 file changed, 17 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/exynos/exynos7.dtsi b/arch/arm64/boot/dts/exynos/exynos7.dtsi
>> index 50ae936..444dde1 100644
>> --- a/arch/arm64/boot/dts/exynos/exynos7.dtsi
>> +++ b/arch/arm64/boot/dts/exynos/exynos7.dtsi
>> @@ -37,6 +37,7 @@
>> compatible = "arm,cortex-a57", "arm,armv8";
>> enable-method = "psci";
>> reg = <0x0>;
>> + cpu-idle-states = <&CPU_SLEEP>;
>> };
>>
>> cpu@1 {
>> @@ -44,6 +45,7 @@
>> compatible = "arm,cortex-a57", "arm,armv8";
>> enable-method = "psci";
>> reg = <0x1>;
>> + cpu-idle-states = <&CPU_SLEEP>;
>> };
>>
>> cpu@2 {
>> @@ -51,6 +53,7 @@
>> compatible = "arm,cortex-a57", "arm,armv8";
>> enable-method = "psci";
>> reg = <0x2>;
>> + cpu-idle-states = <&CPU_SLEEP>;
>> };
>>
>> cpu@3 {
>> @@ -58,6 +61,20 @@
>> compatible = "arm,cortex-a57", "arm,armv8";
>> enable-method = "psci";
>> reg = <0x3>;
>> + cpu-idle-states = <&CPU_SLEEP>;
>> + };
>> +
>> + idle-states {
>> + entry-method = "arm,psci";
>> +
>> + CPU_SLEEP: cpu-sleep {
>> + compatible = "arm,idle-state";
>> + local-timer-stop;
>> + arm,psci-suspend-param = <0x0010000>;
>> + entry-latency-us = <20>;
>> + exit-latency-us = <150>;
>> + min-residency-us = <2100>;
>> + };
>> };
>> };
>>
>> --
>> 1.7.9.5
>>
>>
>
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
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