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

[Leonard Crestez <leonard.crestez@nxp.com>]

On Mon, 2019-11-04 at 16:01 -0600, Rob Herring wrote:
> 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 <leonard.crestez@nxp.com>
> > ---
> >  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.

This driver doesn't actually map registers, they're only touched from
firmware.

Information is from memory map.

> > +			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.

That looks much nicer, fixed in v4.

I had to also update yaml to explicitly allow an "opp-table" child.

--
Regards,
Leonard