On Tue, 30 Sep 2014, Kevin Hilman wrote:

Lorenzo Pieralisi [off-list ref] writes:

quoted

Hi Lina,

On Sat, Sep 27, 2014 at 01:58:13AM +0100, Lina Iyer wrote:

quoted

Add cpuidle driver interface to allow cpus to go into C-States. Use the
cpuidle DT interface common across ARM architectures to provide the
C-State information to the cpuidle framework.

Supported modes at this time are clock gating (wfi) and cpu power down
(Standalone PC or spc).

Signed-off-by: Lina Iyer <redacted>
---
 .../bindings/arm/msm/qcom,idle-state.txt           | 72 +++++++++++++++++
 drivers/cpuidle/Kconfig.arm                        |  7 ++
 drivers/cpuidle/Makefile                           |  1 +
 drivers/cpuidle/cpuidle-qcom.c                     | 89 ++++++++++++++++++++++
 4 files changed, 169 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
 create mode 100644 drivers/cpuidle/cpuidle-qcom.c

diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
new file mode 100644
index 0000000..47095b9
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt

@@ -0,0 +1,72 @@
+QCOM Idle States for cpuidle driver
+
+ARM provides idle-state node to define the cpuidle states, as defined in [1].
+cpuidle-qcom is the cpuidle driver for Qualcomm SoCs and uses these idle
+states. Idle states have different enter/exit latency and residency values.
+The idle states supported by the QCOM SoC are defined as -
+
+    * WFI
+    * Retention
+    * Standalone Power Collapse (Standalone PC or SPC)
+    * Power Collapse (PC)
+
+WFI: WFI does a little more in addition to architectural clock gating.  ARM

This may be misleading. Call it PlatformWFI or something like that, not WFI if
that's not what it is.

This gets at a little pet peeve of mine: 

IMO, naming any state with "WFI" is a bit confusing, because typically
*every* idle state is entered by one (or more) CPU executing WFI, no?

Agreed.

The only state called "WFI" should be the one that only executes the WFI 
instruction without any other hardware setup around it.


Nicolas