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SubjectRe: [PATCHv1 7/8] arm64: dts: qcom: msm8998: Add PSCI cpuidle low power states
On Fri, May 10, 2019 at 04:59:45PM +0530, Amit Kucheria wrote:
> Add device bindings for cpuidle states for cpu devices.
>
> Cc: Marc Gonzalez <marc.w.gonzalez@free.fr>
> Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
> ---
> arch/arm64/boot/dts/qcom/msm8998.dtsi | 32 +++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/qcom/msm8998.dtsi b/arch/arm64/boot/dts/qcom/msm8998.dtsi
> index 3fd0769fe648..208281f318e2 100644
> --- a/arch/arm64/boot/dts/qcom/msm8998.dtsi
> +++ b/arch/arm64/boot/dts/qcom/msm8998.dtsi
> @@ -78,6 +78,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x0>;
> enable-method = "psci";
> + cpu-idle-states = <&LITTLE_CPU_PD>;
> efficiency = <1024>;
> next-level-cache = <&L2_0>;
> L2_0: l2-cache {
> @@ -97,6 +98,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x1>;
> enable-method = "psci";
> + cpu-idle-states = <&LITTLE_CPU_PD>;
> efficiency = <1024>;
> next-level-cache = <&L2_0>;
> L1_I_1: l1-icache {
> @@ -112,6 +114,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x2>;
> enable-method = "psci";
> + cpu-idle-states = <&LITTLE_CPU_PD>;
> efficiency = <1024>;
> next-level-cache = <&L2_0>;
> L1_I_2: l1-icache {
> @@ -127,6 +130,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x3>;
> enable-method = "psci";
> + cpu-idle-states = <&LITTLE_CPU_PD>;
> efficiency = <1024>;
> next-level-cache = <&L2_0>;
> L1_I_3: l1-icache {
> @@ -142,6 +146,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x100>;
> enable-method = "psci";
> + cpu-idle-states = <&BIG_CPU_PD>;
> efficiency = <1536>;
> next-level-cache = <&L2_1>;
> L2_1: l2-cache {
> @@ -161,6 +166,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x101>;
> enable-method = "psci";
> + cpu-idle-states = <&BIG_CPU_PD>;
> efficiency = <1536>;
> next-level-cache = <&L2_1>;
> L1_I_101: l1-icache {
> @@ -176,6 +182,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x102>;
> enable-method = "psci";
> + cpu-idle-states = <&BIG_CPU_PD>;
> efficiency = <1536>;
> next-level-cache = <&L2_1>;
> L1_I_102: l1-icache {
> @@ -191,6 +198,7 @@
> compatible = "arm,armv8";
> reg = <0x0 0x103>;
> enable-method = "psci";
> + cpu-idle-states = <&BIG_CPU_PD>;
> efficiency = <1536>;
> next-level-cache = <&L2_1>;
> L1_I_103: l1-icache {
> @@ -238,6 +246,30 @@
> };
> };
> };
> +
> + idle-states {
> + entry-method="psci";

Please add a space before and after "=".

> +
> + LITTLE_CPU_PD: little-power-down {

In Documentation/devicetree/bindings/arm/idle-states.txt
they seem to use labels such as CPU_SLEEP_0_0 for the first
cluster and CPU_SLEEP_1_0 for the second cluster.

Please also consider my comment in patch 4/8.

> + compatible = "arm,idle-state";
> + idle-state-name = "little-power-down";

Since all other idle-state-name in this series uses the qualcomm
terminology for idle states, I think this should as well.

> + arm,psci-suspend-param = <0x00000002>;

PSCI suspend param 0x2 is actually "retention":
https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/arch/arm/boot/dts/qcom/msm8998-pm.dtsi?h=msm-4.4#n155

So it actually feels incorrect to call this "power-down".

All other patches in this series has added support for standalone power
collapse, so why not add support for SPC rather than retention?

(For SPC arm,psci-suspend-param should be <0x40000003> .)

> + entry-latency-us = <43>;
> + exit-latency-us = <43>;

Shouldn't the latency be <86> ?
https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/arch/arm/boot/dts/qcom/msm8998-pm.dtsi?h=msm-4.4#n157
AFAICT downstream assigns the exit_latency to what is parses from "qcom,latency-us":
https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/drivers/cpuidle/lpm-levels.c?h=msm-4.4#n1712

> + min-residency-us = <200>;
> + local-timer-stop;

Are you sure that the local timer is stopped?
the equivalent DT property to "local-timer-stop" in downstream is
"qcom,use-broadcast-timer", and this property seems to be missing
from this node:
https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/arch/arm/boot/dts/qcom/msm8998-pm.dtsi?h=msm-4.4#n153

You could try to remove "local-timer-stop", if it is really needed,
then the system should hang without this property.

> + };
> +
> + BIG_CPU_PD: big-power-down {
> + compatible = "arm,idle-state";
> + idle-state-name = "big-power-down";
> + arm,psci-suspend-param = <0x00000002>;
> + entry-latency-us = <41>;
> + exit-latency-us = <41>;
> + min-residency-us = <200>;
> + local-timer-stop;
> + };
> + };
> };
>
> firmware {
> --
> 2.17.1
>

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