On Wed, Mar 08, 2023 at 10:35:17PM +0100, Konrad Dybcio wrote: > Disabling RPMCC clocks can be a bit touchy. If we can't guarantee all > (or at least most) of the oneline peripherals ask the interconnect > framework to keep their buses online and guarantee enough bandwidth, > we're relying on bootloader defaults to keep the said buses alive through > RPM requests and rate setting on RPM clocks. > > Without that in place, the RPM clocks are never enabled in the CCF, which > qualifies them to be cleaned up, since - as far as Linux is concerned - > nobody's using them and they're just wasting power. Doing so will end > tragically, as within miliseconds we'll get *some* access attempt on an > unlocked bus which will cause a platform crash. > > On the other hand, if we want to save power and put well-supported > platforms to sleep, we should be shutting off at least some of these > clocks (this time with a clear distinction of which ones are *actually* > not in use, coming from the interconnect driver). > > To differentiate between these two cases while not breaking older DTs, > introduce an opt-in property to correctly mark RPM clocks as enabled > after handoff (the initial max freq vote) and hence qualify them for the > common unused clock cleanup. > > Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx> > --- > Documentation/devicetree/bindings/clock/qcom,rpmcc.yaml | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/devicetree/bindings/clock/qcom,rpmcc.yaml b/Documentation/devicetree/bindings/clock/qcom,rpmcc.yaml > index 2a95bf8664f9..386153f61971 100644 > --- a/Documentation/devicetree/bindings/clock/qcom,rpmcc.yaml > +++ b/Documentation/devicetree/bindings/clock/qcom,rpmcc.yaml > @@ -58,6 +58,12 @@ properties: > minItems: 1 > maxItems: 2 > > + qcom,clk-disable-unused: This is a Linux implementation detail, not a description of the hardware. So it unfortunately doesn't belong here. > + type: boolean > + description: > + Indicates whether unused RPM clocks can be shut down with the common > + unused clock cleanup. Requires a functional interconnect driver. This is an interesting aspect though, there's a lot of things that will break if any one of these building blocks are missing, for any reason. Regards, Bjorn > + > required: > - compatible > - '#clock-cells' > > -- > 2.39.2 >
