Re: [PATCH 2/2] arm64: dts: qcom: sc7280: Add cpu OPP tables

[Sibi Sankar]

Hey Sudeep,

Thanks for the review!

On 2021-05-04 20:12, Sudeep Holla wrote:
> On Fri, Apr 30, 2021 at 07:58:21PM +0530, Sibi Sankar wrote:
> > Add OPP tables required to scale DDR/L3 per freq-domain on SC7280 
> > SoCs.
> >
> > Signed-off-by: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
> > ---
> >  arch/arm64/boot/dts/qcom/sc7280.dtsi | 135 
> > +++++++++++++++++++++++++++++++++++
> >  1 file changed, 135 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi 
> > b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > index 0bb835aeae33..90220cecb368 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
>
>
> [...]
>
> > @@ -248,6 +273,116 @@
> >  		};
> >  	};
> >
> > +	cpu0_opp_table: cpu0_opp_table {
> > +		compatible = "operating-points-v2";
> > +		opp-shared;
> > +
> > +		cpu0_opp1: opp-300000000 {
> > +			opp-hz = /bits/ 64 <300000000>;
> > +			opp-peak-kBps = <800000 9600000>;
> > +		};
> > +
> > +		cpu0_opp2: opp-691200000 {
> > +			opp-hz = /bits/ 64 <691200000>;
> > +			opp-peak-kBps = <800000 17817600>;
> > +		};
> > +
> > +		cpu0_opp3: opp-806400000 {
> > +			opp-hz = /bits/ 64 <806400000>;
> > +			opp-peak-kBps = <800000 20889600>;
> > +		};
> > +
> > +		cpu0_opp4: opp-940800000 {
> > +			opp-hz = /bits/ 64 <940800000>;
> > +			opp-peak-kBps = <1804000 24576000>;
> > +		};
> > +
> > +		cpu0_opp5: opp-1152000000 {
> > +			opp-hz = /bits/ 64 <1152000000>;
> > +			opp-peak-kBps = <2188000 27033600>;
> > +		};
> > +
> > +		cpu0_opp6: opp-1324800000 {
> > +			opp-hz = /bits/ 64 <1324800000>;
> > +			opp-peak-kBps = <2188000 33792000>;
> > +		};
> > +
> > +		cpu0_opp7: opp-1516800000 {
> > +			opp-hz = /bits/ 64 <1516800000>;
> > +			opp-peak-kBps = <3072000 38092800>;
> > +		};
> > +
> > +		cpu0_opp8: opp-1651200000 {
> > +			opp-hz = /bits/ 64 <1651200000>;
> > +			opp-peak-kBps = <3072000 41779200>;
> > +		};
> > +
> > +		cpu0_opp9: opp-1804800000 {
> > +			opp-hz = /bits/ 64 <1804800000>;
> > +			opp-peak-kBps = <4068000 48537600>;
> > +		};
> > +
> > +		cpu0_opp10: opp-1958400000 {
> > +			opp-hz = /bits/ 64 <1958400000>;
> > +			opp-peak-kBps = <4068000 48537600>;
> > +		};
> > +	};
> > +
>
> NACK, this breaks if there is a mismatch from what is read from the 
> hardware
> and what is presented in this table above. Either add it from the some
> bootloader or other boot code to this table reading from the 
> hardware/firmware
> or find a way to link them without this.
>
> Sorry I had warned long back about this when such links were discussed 
> as
> part of interconnect binding.

Not sure why this warrants a NACK,
as this was consensus for mapping
cpu freq to DDR/L3 bandwidth votes.
(We use the same solution on SDM845
and SC7180). The opp tables are
optional and when specified puts in
votes for DDR/L3. In the future the
table can be safely dropped when more
useful devfreq governors are upstreamed.

cpufreq: qcom: Don't add frequencies without an OPP

I guess your main concern for breakage
is ^^ commit? The original design is
to list a super set of frequencies
supported by all variants of the SoC
along with the required DDR/L3 bandwidth
values. When we run into non-documented
frequency we just wouldn't put in bw
votes for it which should be fine since
the entire opp_table is optional. If
this is the reason for the NACK I can
try get it reverted with Matthias's ack.


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