Re: [PATCH] arch: arm64: dts: apq8016-dbc: Add missing cpu opps

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 02 Apr 01:13 PDT 2020, Stephan Gerhold wrote:

> Hi,
> 
> On Wed, Apr 01, 2020 at 07:50:59PM +0200, Loic Poulain wrote:
> > The highest cpu frequency opps have been dropped because CPR is not
> > supported. However, we can simply specify operating voltage so that
> > they match the max corner voltages for each freq. With that, we can
> > support up to 1.36Ghz. Ideally, msm8916 CPR should be implemented to
> > fine tune operating voltages and optimize power consumption.
> 
> Thanks for the patch! I was wondering how to enable the higher CPU
> frequencies for a while now...
> 
> I was actually quite excited to see CPR being mainlined for QCS404.
> If we are trying to add such a workaround (rather than CPR) for MSM8916
> now, does that mean it's unlikely to see CPR working for MSM8916
> anytime soon?
> 
> AFAICT, there is a WIP branch from Niklas Cassel here:
> https://git.linaro.org/people/nicolas.dechesne/niklas.cassel/kernel.git/log/?h=cpr-msm8916-mainline
> but it hasn't been updated for a while. (Not sure if it was working
> already...)
> 
> Can someone explain what is missing to make CPR work for MSM8916?
> 

CPR needs to control 3 things; VDD_APC, VDD_MX and MEMACC. On QCS404 it
seems we don't have to adjust VDD_MX, so the code for this is missing
from the driver.

So, afaict, what's missing is that rpmpd.c needs to gain support for
8916, then the CPR driver needs to gain a cpr_acc_desc and compatible
for 8916, it needs to reference the VDDMX power domain and before/after
we're adjusting the corner of the CPR we need to adjust the MX according
to the mapping specified in the downstream kernel (i.e.  1->4, 2->5 and
3->7).


Unfortunately, the requirement that VDDMX (VDD_MEM I presume) must be
higher than VDD_APC most likely needs to be taken into consideration for
Loic's proposed static voltage scaling as well. Unless VDD_MEM is left
in Turbo mode from the boot loader I think we need to take VDDMX to
corner 7 for speeds 998MHz and above (i.e. where we pull VDD_APC to
1.35V).

Regards,
Bjorn

> One other minor comment/question below.
> 
> > 
> > This patch:
> > - Adds missing opps and corresponding target voltages to msm8916.dtsi.
> > - Adds cpu-supply to apq8016-sbc.dtsi (board level info).
> > - Adds pm8916 spmi regulator node to pm8916.dtsi.
> > 
> > Tested with a dragonboard-410c.
> > 
> > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi | 24 ++++++++++++++++++++++++
> >  arch/arm64/boot/dts/qcom/msm8916.dtsi     | 24 ++++++++++++++++++++++++
> >  arch/arm64/boot/dts/qcom/pm8916.dtsi      |  6 ++++++
> >  3 files changed, 54 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi b/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi
> > index 037e26b..f1c1216 100644
> > --- a/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi
> > @@ -560,6 +560,30 @@
> >  	qcom,mbhc-vthreshold-high = <75 150 237 450 500>;
> >  };
> >  
> > +&spm_regulators {
> > +	vdd_cpu: s2 {
> > +		regulator-always-on;
> > +		regulator-min-microvolt = <1050000>;
> > +		regulator-max-microvolt = <1350000>;
> > +	};
> > +};
> > +
> > +&CPU0 {
> > +	cpu-supply = <&vdd_cpu>;
> > +};
> > +
> > +&CPU1 {
> > +	cpu-supply = <&vdd_cpu>;
> > +};
> > +
> > +&CPU2 {
> > +	cpu-supply = <&vdd_cpu>;
> > +};
> > +
> > +&CPU3 {
> > +	cpu-supply = <&vdd_cpu>;
> > +};
> > +
> 
> I'm a bit confused about the separation here. The cpu-supply is defined
> in the board-specific device tree, yet the voltages are set in the
> common device tree below.
> 
> Is it even possible that the CPU is supplied by something other than S2
> and if yes, how likely is this?
> 
> I'm asking because I have two other MSM8916 devices in mainline
> (and a few more pending upstreaming), and it seems like I would need to
> duplicate this into each of them.
> 
> Thanks,
> Stephan
> 
> >  &smd_rpm_regulators {
> >  	vdd_l1_l2_l3-supply = <&pm8916_s3>;
> >  	vdd_l5-supply = <&pm8916_s3>;
> > diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi b/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > index 9f31064..9805af0 100644
> > --- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
> > @@ -342,15 +342,39 @@
> >  
> >  		opp-200000000 {
> >  			opp-hz = /bits/ 64 <200000000>;
> > +			opp-microvolt = <1050000>;
> >  		};
> >  		opp-400000000 {
> >  			opp-hz = /bits/ 64 <400000000>;
> > +			opp-microvolt = <1050000>;
> > +		};
> > +		opp-533330000 {
> > +			opp-hz = /bits/ 64 <533330000>;
> > +			opp-microvolt = <1150000>;
> >  		};
> >  		opp-800000000 {
> >  			opp-hz = /bits/ 64 <800000000>;
> > +			opp-microvolt = <1150000>;
> >  		};
> >  		opp-998400000 {
> >  			opp-hz = /bits/ 64 <998400000>;
> > +			opp-microvolt = <1350000>;
> > +		};
> > +		opp-1094400000 {
> > +			opp-hz = /bits/ 64 <1094400000>;
> > +			opp-microvolt = <1350000>;
> > +		};
> > +		opp-1152000000 {
> > +			opp-hz = /bits/ 64 <1152000000>;
> > +			opp-microvolt = <1350000>;
> > +		};
> > +		opp-1209600000 {
> > +			opp-hz = /bits/ 64 <1209600000>;
> > +			opp-microvolt = <1350000>;
> > +		};
> > +		opp-1363200000 {
> > +			opp-hz = /bits/ 64 <1363200000>;
> > +			opp-microvolt = <1350000>;
> >  		};
> >  	};
> >  
> > diff --git a/arch/arm64/boot/dts/qcom/pm8916.dtsi b/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > index 0bcdf04..c9b9c4f 100644
> > --- a/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > @@ -157,5 +157,11 @@
> >  			vdd-micbias-supply = <&pm8916_l13>;
> >  			#sound-dai-cells = <1>;
> >  		};
> > +
> > +		spm_regulators: spm_regulators  {
> > +			compatible = "qcom,pm8916-regulators";
> > +			#address-cells = <1>;
> > +			#size-cells = <1>;
> > +		};
> >  	};
> >  };
> > -- 
> > 2.7.4
> >