Re: [PATCH v4] arm64: dts: exynos7: add support for cpuidle core power down

From: Lorenzo Pieralisi
Date: Fri Nov 07 2014 - 06:59:09 EST


On Wed, Nov 05, 2014 at 01:15:31PM +0000, Chander Kashyap wrote:
> Exynos7 has core power down state where cores can be powered off independently.

"...has a core power down idle state..."

> This patch adds support for this state.

"...for this idle 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 for measuring the time.
> 3. Select the worst case time in the set of 100000 cpuidle transactions,
> with varying load.
>
> Exit latency and target residency are supplied as per HW team

"Exit latency and min residency values are supplied by the HW team."

Target residency is a kernel naming scheme, non-existent in the idle state
bindings.

Please take time to write proper commit logs, thanks.

> Signed-off-by: Chander Kashyap <k.chander@xxxxxxxxxxx>
> ---
> 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.
> Changes in v4:
> - Corrected the commit message.
> - Corrected the entry latency value.
>
> 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";

enable-method should be after reg, it is not an ordering issues added
by this patch but I still do not like that.

Other than that, please take some time to rewrite the commit log and
ask to fix the ordering above, you can add my:

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>

> 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 = <34>;
> + exit-latency-us = <150>;
> + min-residency-us = <2100>;
> + };
> };
> };
>
> --
> 1.7.9.5
>
>
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