Subject: Re: [PATCH v3 6/6] arm64: dts: imx8m: Add ddr controller nodes

From: Rob Herring <[email-masked]>
Date: Mon, 4 Nov 2019 16:01:44 -0600

On Thu, Oct 31, 2019 at 11:50:27PM +0200, Leonard Crestez wrote:
> This is used by the imx-ddrc devfreq driver to implement dynamic
> frequency scaling of DRAM.
> 
> Add a devfreq-event link to the dram PMU in order to support on-demand
> scaling of ddrc based on measured dram bandwidth usage.
> 
> Support for proactive scaling via interconnect will come later. The
> high-performance bus masters which need that (display, vpu, gpu) are not
> yet enabled in upstream anyway.
> 
> Signed-off-by: Leonard Crestez <[email-masked]>
> ---
>  arch/arm64/boot/dts/freescale/imx8mm-evk.dts  | 18 ++++++++++++++
>  arch/arm64/boot/dts/freescale/imx8mm.dtsi     | 17 ++++++++++++-
>  .../boot/dts/freescale/imx8mn-ddr4-evk.dts    | 18 ++++++++++++++
>  arch/arm64/boot/dts/freescale/imx8mn.dtsi     | 16 ++++++++++++-
>  arch/arm64/boot/dts/freescale/imx8mq-evk.dts  | 24 +++++++++++++++++++
>  arch/arm64/boot/dts/freescale/imx8mq.dtsi     | 16 ++++++++++++-
>  6 files changed, 106 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-evk.dts b/arch/arm64/boot/dts/freescale/imx8mm-evk.dts
> index 4f5e408d6e6a..be9abd8e4478 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mm-evk.dts
> @@ -69,16 +69,34 @@
>  		simple-audio-card,codec {
>  			sound-dai = <&wm8524>;
>  			clocks = <&clk IMX8MM_CLK_SAI3_ROOT>;
>  		};
>  	};
> +
> +	ddrc_opp_table: ddrc-opp-table {
> +		compatible = "operating-points-v2";
> +
> +		opp-25M {
> +			opp-hz = /bits/ 64 <25000000>;
> +		};
> +		opp-100M {
> +			opp-hz = /bits/ 64 <100000000>;
> +		};
> +		opp-750M {
> +			opp-hz = /bits/ 64 <750000000>;
> +		};
> +	};
>  };
>  
>  &A53_0 {
>  	cpu-supply = <&buck2_reg>;
>  };
>  
> +&ddrc {
> +	operating-points-v2 = <&ddrc_opp_table>;
> +};
> +
>  &fec1 {
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_fec1>;
>  	phy-mode = "rgmii-id";
>  	phy-handle = <&ethphy0>;
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> index 6edbdfe2d0d7..5404870d80d5 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> @@ -856,11 +856,26 @@
>  			#interrupt-cells = <3>;
>  			interrupt-controller;
>  			interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
>  		};
>  
> -		ddr-pmu@3d800000 {
> +		ddrc: dram-controller@3d400000 {
> +			compatible = "fsl,imx8mm-ddrc", "fsl,imx8m-ddrc";
> +			reg = <0x3d400000 0x400000>;

Do you really need the OS to map 4MB of register space? Virtual 
space on 64-bit doesn't matter, but it's still wasting 2KB of memory 
just to map all that if only a few pages are needed. Adds up if the 
whole DT is done this way.

> +			clock-names = "dram_core",
> +				      "dram_pll",
> +				      "dram_alt",
> +				      "dram_apb";
> +			clocks = <&clk IMX8MM_CLK_DRAM_CORE>,
> +				 <&clk IMX8MM_DRAM_PLL>,
> +				 <&clk IMX8MM_CLK_DRAM_ALT>,
> +				 <&clk IMX8MM_CLK_DRAM_APB>;
> +			devfreq-events = <&ddr_pmu>;
> +			operating-points-v2 = <&ddrc_opp_table>;
> +		};
> +
> +		ddr_pmu: ddr-pmu@3d800000 {
>  			compatible = "fsl,imx8mm-ddr-pmu", "fsl,imx8m-ddr-pmu";
>  			reg = <0x3d800000 0x400000>;
>  			interrupt-parent = <&gic>;
>  			interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
>  		};
> diff --git a/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts b/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> index 071949412caf..ab2060667671 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> @@ -9,16 +9,34 @@
>  #include "imx8mn-evk.dtsi"
>  
>  / {
>  	model = "NXP i.MX8MNano DDR4 EVK board";
>  	compatible = "fsl,imx8mn-ddr4-evk", "fsl,imx8mn";
> +
> +	ddrc_opp_table: ddrc-opp-table {

I think it would be better to put this under the ddrc node (and named 
'opp-table'). Yes, it's kind of silly to have a phandle to a child node, 
but that still works.

> +		compatible = "operating-points-v2";
> +
> +		opp-25M {
> +			opp-hz = /bits/ 64 <25000000>;
> +		};
> +		opp-100M {
> +			opp-hz = /bits/ 64 <100000000>;
> +		};
> +		opp-600M {
> +			opp-hz = /bits/ 64 <600000000>;
> +		};
> +	};
>  };
>  
>  &A53_0 {
>  	cpu-supply = <&buck2_reg>;
>  };
>  
> +&ddrc {
> +	operating-points-v2 = <&ddrc_opp_table>;
> +};
> +
>  &i2c1 {
>  	pmic@4b {
>  		compatible = "rohm,bd71847";
>  		reg = <0x4b>;
>  		pinctrl-0 = <&pinctrl_pmic>;
> diff --git a/arch/arm64/boot/dts/freescale/imx8mn.dtsi b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> index e91625063f8e..344dd777635f 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> @@ -757,11 +757,25 @@
>  			#interrupt-cells = <3>;
>  			interrupt-controller;
>  			interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
>  		};
>  
> -		ddr-pmu@3d800000 {
> +		ddrc: dram-controller@3d400000 {
> +			compatible = "fsl,imx8mn-ddrc", "fsl,imx8m-ddrc";
> +			reg = <0x3d400000 0x400000>;
> +			clock-names = "dram_core",
> +				      "dram_pll",
> +				      "dram_alt",
> +				      "dram_apb";
> +			clocks = <&clk IMX8MN_CLK_DRAM_CORE>,
> +				 <&clk IMX8MN_DRAM_PLL>,
> +				 <&clk IMX8MN_CLK_DRAM_ALT>,
> +				 <&clk IMX8MN_CLK_DRAM_APB>;
> +			devfreq-events = <&ddr_pmu>;
> +		};
> +
> +		ddr_pmu: ddr-pmu@3d800000 {
>  			compatible = "fsl,imx8mn-ddr-pmu", "fsl,imx8m-ddr-pmu";
>  			reg = <0x3d800000 0x400000>;
>  			interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
>  		};
>  	};
> diff --git a/arch/arm64/boot/dts/freescale/imx8mq-evk.dts b/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> index c36685916683..fc4c12ab8991 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> @@ -85,10 +85,30 @@
>  		link_codec: simple-audio-card,codec {
>  			sound-dai = <&wm8524>;
>  			clocks = <&clk IMX8MQ_CLK_SAI2_ROOT>;
>  		};
>  	};
> +
> +	ddrc_opp_table: ddrc-opp-table {
> +		compatible = "operating-points-v2";
> +
> +		opp-25M {
> +			opp-hz = /bits/ 64 <25000000>;
> +		};
> +		opp-100M {
> +			opp-hz = /bits/ 64 <100000000>;
> +		};
> +		/*
> +		 * On imx8mq B0 PLL can't be bypassed so low bus is 166M
> +		 */
> +		opp-166M {
> +			opp-hz = /bits/ 64 <166935483>;
> +		};
> +		opp-800M {
> +			opp-hz = /bits/ 64 <800000000>;
> +		};
> +	};
>  };
>  
>  &A53_0 {
>  	cpu-supply = <&buck2_reg>;
>  };
> @@ -103,10 +123,14 @@
>  
>  &A53_3 {
>  	cpu-supply = <&buck2_reg>;
>  };
>  
> +&ddrc {
> +	operating-points-v2 = <&ddrc_opp_table>;
> +};
> +
>  &fec1 {
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_fec1>;
>  	phy-mode = "rgmii-id";
>  	phy-handle = <&ethphy0>;
> diff --git a/arch/arm64/boot/dts/freescale/imx8mq.dtsi b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> index 7f9319452b58..6ef1af41ef68 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> @@ -1111,11 +1111,25 @@
>  			interrupt-controller;
>  			interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
>  			interrupt-parent = <&gic>;
>  		};
>  
> -		ddr-pmu@3d800000 {
> +		ddrc: dram-controller@3d400000 {
> +			compatible = "fsl,imx8mq-ddrc", "fsl,imx8m-ddrc";
> +			reg = <0x3d400000 0x400000>;
> +			clock-names = "dram_core",
> +				      "dram_pll",
> +				      "dram_alt",
> +				      "dram_apb";
> +			clocks = <&clk IMX8MQ_CLK_DRAM_CORE>,
> +				 <&clk IMX8MQ_DRAM_PLL_OUT>,
> +				 <&clk IMX8MQ_CLK_DRAM_ALT>,
> +				 <&clk IMX8MQ_CLK_DRAM_APB>;
> +			devfreq-events = <&ddr_pmu>;
> +		};
> +
> +		ddr_pmu: ddr-pmu@3d800000 {
>  			compatible = "fsl,imx8mq-ddr-pmu", "fsl,imx8m-ddr-pmu";
>  			reg = <0x3d800000 0x400000>;
>  			interrupt-parent = <&gic>;
>  			interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
>  		};
> -- 
> 2.17.1
> 

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