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

Hi Lorenzo,

On Wed, Oct 15, 2014 at 2:30 PM, Lorenzo Pieralisi
[off-list ref] wrote:

On Wed, Oct 15, 2014 at 07:35:20AM +0100, Chander Kashyap wrote:

quoted

Exynos7 has core power down state where cores can be powered off independently.
This patch adds support for this state.

Please tell us more about the idle-state values you are adding, in particular
entry, exit latencies and min-residency values.

Entry latency: This value is calculated as follows:

On entry to arm64_enter_idle_state:
timestamp1 = ktimeget();

after returning from cpu_suspend()

timestamp2 = ktimeget();

latency = timestamp2-timestamp1;

Cpu is not allowed to enter core powerdown by skipping wfi instruction at end.
Hence calculated time contains entry time + failure exit time.


Regarding
exit-latency and target-residency time, got these values from HW team.

I am using these as initial values and I will be working on optimizing
these values with further experiments.
If you could suggest any formal method of deriving these values, i can
try those methods as well.

quoted

Signed-off-by: Chander Kashyap <redacted>
---
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
      - [PATCH v9 0/8] ARM generic idle states
              http://permalink.gmane.org/gmane.linux.power-management.general/49224

Series above was merged, so dependency is stale.

i will remove this

quoted

 arch/arm64/boot/dts/exynos/exynos7.dtsi |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)dont

diff --git a/arch/arm64/boot/dts/exynos/exynos7.dtsi b/arch/arm64/boot/dts/exynos/exynos7.dtsi
index ce221ac..8e0a034 100644
--- a/arch/arm64/boot/dts/exynos/exynos7.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos7.dtsi

@@ -36,6 +36,7 @@
                      device_type = "cpu";
                      compatible = "arm,cortex-a57", "arm,armv8";
                      enable-method = "psci";
+                     cpu-idle-states = <&CPU_SLEEP>;

I would add cpu-idle-states phandle after the reg property, as defined
in the idle states bindings.

i will move this after reg property.

quoted

                      reg = <0x0>;
              };

@@ -43,6 +44,7 @@
                      device_type = "cpu";
                      compatible = "arm,cortex-a57", "arm,armv8";
                      enable-method = "psci";
+                     cpu-idle-states = <&CPU_SLEEP>;
                      reg = <0x1>;
              };

@@ -50,6 +52,7 @@
                      device_type = "cpu";
                      compatible = "arm,cortex-a57", "arm,armv8";
                      enable-method = "psci";
+                     cpu-idle-states = <&CPU_SLEEP>;
                      reg = <0x2>;
              };

@@ -57,8 +60,23 @@
                      device_type = "cpu";
                      compatible = "arm,cortex-a57", "arm,armv8";
                      enable-method = "psci";
+                     cpu-idle-states = <&CPU_SLEEP>;
                      reg = <0x3>;
              };
+
+             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>;
+                             status = "enabled";

status ? This is not a documented property. If you need it please explain
why, define its bindings and we can see how to accommodate it.

I will add okay for status property. As per the bindings posted by you.

regards,

Thank you,
Lorenzo

quoted

+                     };
+             };
      };

      psci {
--
1.7.9.5

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel at lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel