On Fri, Jun 10, 2016 at 11:12:34AM -0500, Andy Gross wrote:
> On Fri, Jun 10, 2016 at 04:48:57PM +0100, Mark Rutland wrote:
> > [+ Lorenzo]
> >
> > On Thu, May 19, 2016 at 12:00:18AM -0500, Andy Gross wrote:
> > > This patch adds the qcom,idle-state-spc compatible to the SPC idle
> > > state. This compatible indicates that the state is one which supports
> > > freeze.
> > >
> > > Signed-off-by: Andy Gross <andy.gross@xxxxxxxxxx>
> > > ---
> > > arch/arm64/boot/dts/qcom/msm8916.dtsi | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi b/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > > index 208af00..032e411 100644
> > > --- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > > @@ -104,7 +104,7 @@
> > >
> > > idle-states {
> > > CPU_SPC: spc {
> > > - compatible = "arm,idle-state";
> > > + compatible = "qcom,idle-state-spc", "arm,idle-state";
> > > arm,psci-suspend-param = <0x40000002>;
> > > entry-latency-us = <130>;
> > > exit-latency-us = <150>;
> >
> > This looks suspicious.
> >
> > This is a PSCI idle state, and we have a PSCI driver driven by the
> > generic ARM cpuidle driver.
> >
> > Why do we need a qcom-specific compatible here?
> >
> > Surely we should be able to use the idle code in a generic fashion to
> > driver suspend-to-idle?
>
> We need a way to identify specific idle states that support suspend-to-idle. In
> addition, when we have identified the states, we may have to configure the
> enter_freeze() function.
Could you elaborate on what you mean by a state supporting
suspend-to-idle? It was my understanding that any idle state should
function for suspend-to-idle (and the choice of state is potentially
subjective).
> I chose to do this outside of the arm cpuidle driver because I didn't want to
> add any more DT information aside from the compatible, and I needed a separate
> place for the Qualcomm specific suspend code.
Which suspend code is Qualcomm-specific? There shouldn't be anything on
the PSCI side, so I can only imagine that device management is left.
What am I missing?
> With the compatible, this makes
> my 32 and 64 bit processor suspend code identical, as we have our own cpuidle
> driver for the 32 bit procs.
>
> An alternative would be to add some facilities to communicate this to the arm
> cpuidle driver and configure the enter_freeze() function at some later point.
I would prefer that suspend-to-idle using PSCI occurred via the generic
PSCI and cpuidle code. I am happy to extend that code if there is
something lacking, and I would prefer to not have platform-specific
hooks.
Thanks,
Mark.
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