linux-kernel - Re: [PATCH v2 4/4] dt-bindings: interconnect: qcs404: Introduce qcom,qos DT property

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Message-ID: <20190418225150.GN27005@builder>
Date:   Thu, 18 Apr 2019 15:51:50 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Georgi Djakov <georgi.djakov@...aro.org>
Cc:     robh+dt@...nel.org, vkoul@...nel.org, evgreen@...omium.org,
        daidavid1@...eaurora.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 4/4] dt-bindings: interconnect: qcs404: Introduce
 qcom,qos DT property

On Mon 15 Apr 03:43 PDT 2019, Georgi Djakov wrote:

> There are separate hardware blocks per each interconnect that allow QoS
> configuration to be applied to each port (node). There are different kinds of
> priorities that could be set on these ports. Each port supports also various
> QoS modes such as "fixed", "limiter", "bypass" and "regulator". Depending on
> the mode, there are a few additional knobs that could be configured.
> 
> Introduce the qcom,qos property, so that we describe this relation in DT and
> allow the interconnect provider drivers can make use of it.
> 

As the example shows we will end up with two nodes describing the same
hardware with pretty much identical set of properties.

I really do think it's better to represent and implement the NoC
controllers on the mmio/platform bus and have a small "proxy" as a child
of the RPM.


By doing this you avoid the duplication of the clock properties and you
don't need the qcom,qos reference to pair up each "bus performance
driver" to the "bus qos driver".

And you still maintain the idea that the entity you request bandwidth
votes with are the NoC controller (which also will be the QoS
controller).

Regards,
Bjorn

> Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
> ---
> 
> v2:
> - New patch.
> 
>  .../bindings/interconnect/qcom,qcs404.txt     | 31 +++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/interconnect/qcom,qcs404.txt b/Documentation/devicetree/bindings/interconnect/qcom,qcs404.txt
> index 9befcd14a5b5..b971e0ee2963 100644
> --- a/Documentation/devicetree/bindings/interconnect/qcom,qcs404.txt
> +++ b/Documentation/devicetree/bindings/interconnect/qcom,qcs404.txt
> @@ -11,9 +11,37 @@ Required properties :
>  Optional properties :
>  clocks : list of phandles and specifiers to all interconnect bus clocks
>  clock-names : clock names should include both "bus_clk" and "bus_a_clk"
> +qcom,qos : phandle to the QoS device-tree node
>  
>  Example:
>  
> +soc {
> +	...
> +	bimc_qos: interconnect@...000 {
> +		compatible = "qcom,qcs404-bimc-qos";
> +		reg = <0x400000 0x80000>;
> +		clock-names = "bus_clk", "bus_a_clk";
> +		clocks = <&rpmcc RPM_SMD_BIMC_CLK>,
> +			<&rpmcc RPM_SMD_BIMC_A_CLK>;
> +	};
> +
> +	pcnoc_qos: interconnect@...000 {
> +		compatible = "qcom,qcs404-pcnoc-qos";
> +		reg = <0x500000 0x15080>;
> +		clock-names = "bus_clk", "bus_a_clk";
> +		clocks = <&rpmcc RPM_SMD_PNOC_CLK>,
> +			<&rpmcc RPM_SMD_PNOC_A_CLK>;
> +	};
> +
> +	snoc_qos: interconnect@...000 {
> +		compatible = "qcom,qcs404-snoc-qos";
> +		reg = <0x580000 0x14000>;
> +		clock-names = "bus_clk", "bus_a_clk";
> +		clocks = <&rpmcc RPM_SMD_SNOC_CLK>,
> +			<&rpmcc RPM_SMD_SNOC_A_CLK>;
> +	};
> +};
> +
>  rpm-glink {
>  	...
>  	rpm_requests: glink-channel {
> @@ -24,6 +52,7 @@ rpm-glink {
>  			clock-names = "bus_clk", "bus_a_clk";
>  			clocks = <&rpmcc RPM_SMD_BIMC_CLK>,
>  				<&rpmcc RPM_SMD_BIMC_A_CLK>;
> +			qcom,qos = <&bimc_qos>;
>  		};
>  
>  		pnoc: interconnect@1 {
> @@ -32,6 +61,7 @@ rpm-glink {
>  			clock-names = "bus_clk", "bus_a_clk";
>  			clocks = <&rpmcc RPM_SMD_PNOC_CLK>,
>  				<&rpmcc RPM_SMD_PNOC_A_CLK>;
> +			qcom,qos = <&pcnoc_qos>;
>  		};
>  
>  		snoc: interconnect@2 {
> @@ -40,6 +70,7 @@ rpm-glink {
>  			clock-names = "bus_clk", "bus_a_clk";
>  			clocks = <&rpmcc RPM_SMD_SNOC_CLK>,
>  				<&rpmcc RPM_SMD_SNOC_A_CLK>;
> +			qcom,qos = <&snoc_qos>;
>  		};
>  	};
>  };