[PATCH v7 5/7] qcom: cpuidle: Add cpuidle driver for QCOM cpus

[Nicolas Pitre]

On Tue, 30 Sep 2014, Kevin Hilman wrote:

> On Tue, Sep 30, 2014 at 10:51 AM, Nicolas Pitre
> <nicolas.pitre at linaro.org> wrote:
> > On Tue, 30 Sep 2014, Kevin Hilman wrote:
> >
> >> Lorenzo Pieralisi <lorenzo.pieralisi at arm.com> writes:
> >>
> >> > Hi Lina,
> >> >
> >> > On Sat, Sep 27, 2014 at 01:58:13AM +0100, Lina Iyer wrote:
> >> >> 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 <lina.iyer at linaro.org>
> >> >> ---
> >> >>  .../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.
> 
> Well, I would go even further in that none of the states should be
> called WFI, because WFI is used to enter all of them.

Fair enough.

So let's fix this by finding a name for that state that consists of only 
executing WFI and that every SOC has.

Suggestions?


Nicolas