linux-kernel - Re: [RFC PATCH v3 1/2] dt-bindings: nand: meson: add Amlogic NAND controller driver

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Date:   Fri, 7 Sep 2018 14:19:44 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Jianxin Pan <jianxin.pan@...ogic.com>
Cc:     <linux-mtd@...ts.infradead.org>,
        Liang Yang <liang.yang@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh@...nel.org>, Jian Hu <jian.hu@...ogic.com>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH v3 1/2] dt-bindings: nand: meson: add Amlogic NAND
 controller driver

On Fri, 7 Sep 2018 18:57:10 +0800
Jianxin Pan <jianxin.pan@...ogic.com> wrote:

> From: Liang Yang <liang.yang@...ogic.com>
> 
> Add Amlogic NAND controller dt-bindings for Meson SoC,
> Current this driver support GXBB/GXL/AXG platform.
> 
> Signed-off-by: Liang Yang <liang.yang@...ogic.com>
> Signed-off-by: Yixun Lan <yixun.lan@...ogic.com>
> ---
>  .../devicetree/bindings/mtd/amlogic,meson-nand.txt | 91 ++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/amlogic,meson-nand.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.txt b/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.txt
> new file mode 100644
> index 0000000..655a778
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.txt
> @@ -0,0 +1,91 @@
> +Amlogic NAND Flash Controller (NFC) for GXBB/GXL/AXG family SoCs
> +
> +This file documents the properties in addition to those available in
> +the MTD NAND bindings.
> +
> +Required properties:
> +- compatible : contains one of:
> +  - "amlogic,meson-gxl-nfc"
> +  - "amlogic,meson-axg-nfc"
> +- clocks     :
> +	A list of phandle + clock-specifier pairs for the clocks listed
> +	in clock-names.
> +
> +- clock-names: Should contain the following:
> +	"core" - NFC module gate clock
> +	"device" - device clock from eMMC sub clock controller
> +
> +- pins     : Select pins which NFC need.
> +- nand_pins: Detail NAND pins information.

You mean pinctrl-names and pinctrl-0, right? Not sure it's necessary to
document that, but if you do, please use the correct DT prop names.

> +- amlogic,mmc-syscon	: Required for NAND clocks, it's shared with SD/eMMC
> +				controller port C
> +
> +Optional children nodes:
> +Children nodes represent the available nand chips.
> +
> +
> +

One too many blank lines here.

> +Other properties:
> +see Documentation/devicetree/bindings/mtd/nand.txt for generic bindings.
> +
> +Example demonstrate on AXG SoC:
> +
> +	sd_emmc_c_clkc: mmc@...0 {
> +		compatible = "amlogic,meson-axg-mmc-clkc", "syscon";
> +		reg = <0x0 0x7000 0x0 0x800>;
> +		status = "okay";
> +	};
> +
> +	nand: nfc@...0 {
> +		compatible = "amlogic,meson-axg-nfc";
> +		reg = <0x0 0x7800 0x0 0x100>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		interrupts = <GIC_SPI 34 IRQ_TYPE_EDGE_RISING>;
> +		status = "disabled";
> +
> +		clocks = <&clkc CLKID_SD_EMMC_C>,
> +			<&sd_emmc_c_clkc CLKID_MMC_DIV>;
> +		clock-names = "core", "device";
> +		amlogic,mmc-syscon = <&sd_emmc_c_clkc>;
> +
> +		status = "okay";
> +
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&nand_pins>;
> +
> +		nand@0 {
> +			reg = <0>;
> +			#address-cells = <1>;
> +			#size-cells = <1>;
> +
> +			nand-on-flash-bbt;
> +			nand-ecc-mode = "hw";
> +			nand-ecc-strength = <8>;
> +			nand-ecc-step-size = <1024>;

Drop nand-ecc- props. I guess you have a sensible default value and I
prefer when ECC requirements are directly extracted during chip
detection. Defining that in the DT is a bad habit. The only one that
could make sense (assuming you support it) is nand-ecc-maximize.

> +
> +			amlogic,nand-enable-scrambler;

Please drop this property (it's not longer documented).

> +
> +			partition@0 {
> +				label = "boot";
> +				reg = <0x00000000 0x00200000>;
> +				read-only;
> +			};
> +			partition@...000 {
> +				label = "env";
> +				reg = <0x00200000 0x00400000>;
> +			};
> +			partition@...000 {
> +				label = "system";
> +				reg = <0x00600000 0x00a00000>;
> +			};
> +			partition@...0000 {
> +				label = "rootfs";
> +				reg = <0x01000000 0x03000000>;
> +			};
> +			partition@...0000 {
> +				label = "media";
> +				reg = <0x04000000 0x8000000>;
> +			};

No need to define the partitions in your example, especially since they
should be placed in a partitions subnode with a "fixed-partitions"
compat.

> +		};
> +	};