linux-kernel - Re: [PATCH v3 03/17] arm64: dts: sdm845: Add OPP table for all qup devices

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Message-ID: <20200429000234.GK4525@google.com>
Date:   Tue, 28 Apr 2020 17:02:34 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        bjorn.andersson@...aro.org, agross@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH v3 03/17] arm64: dts: sdm845: Add OPP table for all qup
 devices

Hi Rajendra,

On Tue, Apr 28, 2020 at 07:02:51PM +0530, Rajendra Nayak wrote:
> qup has a requirement to vote on the performance state of the CX domain
> in sdm845 devices. Add OPP tables for these and also add power-domains
> property for all qup instances.
> 
> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  arch/arm64/boot/dts/qcom/sdm845.dtsi | 115 +++++++++++++++++++++++++++++++++++
>  1 file changed, 115 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> index 8f926b5..36b9fb1 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> @@ -804,6 +804,25 @@
>  			clock-names = "core";
>  		};
>  
> +		qup_opp_table: qup-opp-table {
> +			compatible = "operating-points-v2";
> +
> +			opp-19200000 {
> +				opp-hz = /bits/ 64 <19200000>;
> +				required-opps = <&rpmhpd_opp_min_svs>;
> +			};
> +
> +			opp-75000000 {
> +				opp-hz = /bits/ 64 <75000000>;
> +				required-opps = <&rpmhpd_opp_low_svs>;
> +			};
> +
> +			opp-100000000 {
> +				opp-hz = /bits/ 64 <100000000>;
> +				required-opps = <&rpmhpd_opp_svs>;
> +			};
> +		};
> +

Judging from SDM845 (which has more OPP tables) the convention seems to be
to add OPP tables to the nodes that use them, which seems reasonable and
keeps them out of the device list.

Unfortunately this convention isn't completely suitable for cases like this
(and the DSI OPPs later in this series), where the same OPP table is used by
multiple devices. A possible compromise would be to add the table to the
node of the first device that uses them.