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Date:   Tue, 7 Sep 2021 16:03:17 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Roger Quadros <rogerq@kernel.org>
Cc:     tony@atomide.com, robh+dt@kernel.org, grygorii.strashko@ti.com,
        nm@ti.com, lokeshvutla@ti.com, nsekhar@ti.com,
        krzysztof.kozlowski@canonical.com, devicetree@vger.kernel.org,
        linux-mtd@lists.infradead.org, linux-omap@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 5/8] dt-bindings: mtd: ti,gpmc-nand: Convert to yaml
Message-ID: <20210907160317.2ec5304a@xps13>
In-Reply-To: <20210907113226.31876-6-rogerq@kernel.org>
References: <20210907113226.31876-1-rogerq@kernel.org>
        <20210907113226.31876-6-rogerq@kernel.org>
Organization: Bootlin
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Hi Roger,

rogerq@kernel.org wrote on Tue,  7 Sep 2021 14:32:23 +0300:

> Convert gpmc-nand.txt to ti,gpmc-nand.yaml.
> 
> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> ---
>  .../devicetree/bindings/mtd/gpmc-nand.txt     | 147 ------------------
>  .../devicetree/bindings/mtd/ti,gpmc-nand.yaml | 110 +++++++++++++
>  2 files changed, 110 insertions(+), 147 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/mtd/gpmc-nand.txt
>  create mode 100644 Documentation/devicetree/bindings/mtd/ti,gpmc-nand.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> deleted file mode 100644
> index 44919d48d241..000000000000
> --- a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> +++ /dev/null
> @@ -1,147 +0,0 @@
> -Device tree bindings for GPMC connected NANDs
> -
> -GPMC connected NAND (found on OMAP boards) are represented as child nodes of
> -the GPMC controller with a name of "nand".
> -
> -All timing relevant properties as well as generic gpmc child properties are
> -explained in a separate documents - please refer to
> -Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
> -
> -For NAND specific properties such as ECC modes or bus width, please refer to
> -Documentation/devicetree/bindings/mtd/nand-controller.yaml
> -
> -
> -Required properties:
> -
> - - compatible:	"ti,omap2-nand"
> - - reg:		range id (CS number), base offset and length of the
> -		NAND I/O space
> - - interrupts:	Two interrupt specifiers, one for fifoevent, one for termcount.
> -
> -Optional properties:
> -
> - - nand-bus-width: 		Set this numeric value to 16 if the hardware
> -				is wired that way. If not specified, a bus
> -				width of 8 is assumed.
> -
> - - ti,nand-ecc-opt:		A string setting the ECC layout to use. One of:
> -		"sw"		1-bit Hamming ecc code via software
> -		"hw"		<deprecated> use "ham1" instead
> -		"hw-romcode"	<deprecated> use "ham1" instead
> -		"ham1"		1-bit Hamming ecc code
> -		"bch4"		4-bit BCH ecc code
> -		"bch8"		8-bit BCH ecc code
> -		"bch16"		16-bit BCH ECC code
> -		Refer below "How to select correct ECC scheme for your device ?"
> -
> - - ti,nand-xfer-type:		A string setting the data transfer type. One of:
> -
> -		"prefetch-polled"	Prefetch polled mode (default)
> -		"polled"		Polled mode, without prefetch
> -		"prefetch-dma"		Prefetch enabled DMA mode
> -		"prefetch-irq"		Prefetch enabled irq mode
> -
> - - elm_id:	<deprecated> use "ti,elm-id" instead
> - - ti,elm-id:	Specifies phandle of the ELM devicetree node.
> -		ELM is an on-chip hardware engine on TI SoC which is used for
> -		locating ECC errors for BCHx algorithms. SoC devices which have
> -		ELM hardware engines should specify this device node in .dtsi
> -		Using ELM for ECC error correction frees some CPU cycles.
> - - rb-gpios:	GPIO specifier for the ready/busy# pin.
> -
> -For inline partition table parsing (optional):
> -
> - - #address-cells: should be set to 1
> - - #size-cells: should be set to 1
> -
> -Example for an AM33xx board:
> -
> -	gpmc: gpmc@50000000 {
> -		compatible = "ti,am3352-gpmc";
> -		ti,hwmods = "gpmc";
> -		reg = <0x50000000 0x36c>;
> -		interrupts = <100>;
> -		gpmc,num-cs = <8>;
> -		gpmc,num-waitpins = <2>;
> -		#address-cells = <2>;
> -		#size-cells = <1>;
> -		ranges = <0 0 0x08000000 0x1000000>;	/* CS0 space, 16MB */
> -		elm_id = <&elm>;
> -		interrupt-controller;
> -		#interrupt-cells = <2>;
> -
> -		nand@0,0 {
> -			compatible = "ti,omap2-nand";
> -			reg = <0 0 4>;		/* CS0, offset 0, NAND I/O window 4 */
> -			interrupt-parent = <&gpmc>;
> -			interrupts = <0 IRQ_TYPE_NONE>, <1 IRQ_TYPE NONE>;
> -			nand-bus-width = <16>;
> -			ti,nand-ecc-opt = "bch8";
> -			ti,nand-xfer-type = "polled";
> -			rb-gpios = <&gpmc 0 GPIO_ACTIVE_HIGH>; /* gpmc_wait0 */
> -
> -			gpmc,sync-clk-ps = <0>;
> -			gpmc,cs-on-ns = <0>;
> -			gpmc,cs-rd-off-ns = <44>;
> -			gpmc,cs-wr-off-ns = <44>;
> -			gpmc,adv-on-ns = <6>;
> -			gpmc,adv-rd-off-ns = <34>;
> -			gpmc,adv-wr-off-ns = <44>;
> -			gpmc,we-off-ns = <40>;
> -			gpmc,oe-off-ns = <54>;
> -			gpmc,access-ns = <64>;
> -			gpmc,rd-cycle-ns = <82>;
> -			gpmc,wr-cycle-ns = <82>;
> -			gpmc,wr-access-ns = <40>;
> -			gpmc,wr-data-mux-bus-ns = <0>;
> -
> -			#address-cells = <1>;
> -			#size-cells = <1>;
> -
> -			/* partitions go here */
> -		};
> -	};
> -
> -How to select correct ECC scheme for your device ?
> ---------------------------------------------------
> -Higher ECC scheme usually means better protection against bit-flips and
> -increased system lifetime. However, selection of ECC scheme is dependent
> -on various other factors also like;
> -
> -(1) support of built in hardware engines.
> -	Some legacy OMAP SoC do not have ELM harware engine, so those SoC cannot
> -	support ecc-schemes with hardware error-correction (BCHx_HW). However
> -	such SoC can use ecc-schemes with software library for error-correction
> -	(BCHx_HW_DETECTION_SW). The error correction capability with software
> -	library remains equivalent to their hardware counter-part, but there is
> -	slight CPU penalty when too many bit-flips are detected during reads.
> -
> -(2) Device parameters like OOBSIZE.
> -	Other factor which governs the selection of ecc-scheme is oob-size.
> -	Higher ECC schemes require more OOB/Spare area to store ECC syndrome,
> -	so the device should have enough free bytes available its OOB/Spare
> -	area to accommodate ECC for entire page. In general following expression
> -	helps in determining if given device can accommodate ECC syndrome:
> -	"2 + (PAGESIZE / 512) * ECC_BYTES" >= OOBSIZE"
> -	where
> -		OOBSIZE		number of bytes in OOB/spare area
> -		PAGESIZE	number of bytes in main-area of device page
> -		ECC_BYTES	number of ECC bytes generated to protect
> -		                512 bytes of data, which is:
> -				'3' for HAM1_xx ecc schemes
> -				'7' for BCH4_xx ecc schemes
> -				'14' for BCH8_xx ecc schemes
> -				'26' for BCH16_xx ecc schemes
> -
> -	Example(a): For a device with PAGESIZE = 2048 and OOBSIZE = 64 and
> -		trying to use BCH16 (ECC_BYTES=26) ecc-scheme.
> -		Number of ECC bytes per page = (2 + (2048 / 512) * 26) = 106 B
> -		which is greater than capacity of NAND device (OOBSIZE=64)
> -		Hence, BCH16 cannot be supported on given device. But it can
> -		probably use lower ecc-schemes like BCH8.
> -
> -	Example(b): For a device with PAGESIZE = 2048 and OOBSIZE = 128 and
> -		trying to use BCH16 (ECC_BYTES=26) ecc-scheme.
> -		Number of ECC bytes per page = (2 + (2048 / 512) * 26) = 106 B
> -		which can be accommodated in the OOB/Spare area of this device
> -		(OOBSIZE=128). So this device can use BCH16 ecc-scheme.
> diff --git a/Documentation/devicetree/bindings/mtd/ti,gpmc-nand.yaml b/Documentation/devicetree/bindings/mtd/ti,gpmc-nand.yaml
> new file mode 100644
> index 000000000000..db36f2e944ef
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/ti,gpmc-nand.yaml
> @@ -0,0 +1,110 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mtd/ti,gpmc-nand.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Texas Instruments GPMC NAND Flash controller.
> +
> +maintainers:
> +  - Tony Lindgren <tony@atomide.com>
> +  - Roger Quadros <rogerq@kernel.org>
> +
> +description:
> +  GPMC NAND controller/Flash is represented as a child of the
> +  GPMC controller node.
> +
> +properties:
> +  compatible:
> +    const: ti,omap2-nand
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    items:
> +      - description: Interrupt for fifoevent
> +      - description: Interrupt for termcount
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 1
> +
> +  ti,nand-ecc-opt:
> +    description: Desired ECC algorithm
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [sw, ham1, bch4, bch8, bch16]
> +
> +  ti,nand-xfer-type:
> +    description: Data transfer method between controller and chip.
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [prefetch-polled, polled, prefetch-dma, prefetch-irq]
> +    default: prefetch-polled
> +
> +  ti,elm-id:
> +    description:
> +      phandle to the ELM (Error Location Module).
> +    $ref: /schemas/types.yaml#/definitions/phandle

Should perhaps keep the elm-id property documented but set to
'deprecated'.

> +
> +  nand-bus-width:
> +    description:
> +      Bus width to the NAND chip
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [8, 16]
> +    default: 8

This is part of nand-controller.yaml binding and should not be there.

> +
> +allOf:
> +  - $ref: "../memory-controllers/ti,gpmc-child.yaml"

Maybe you need to reference the nand controller bindings as well

> +
> +required:
> +  - compatible
> +  - reg
> +  - ti,nand-ecc-opt
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    gpmc: memory-controller@50000000 {
> +      compatible = "ti,am3352-gpmc";
> +      dmas = <&edma 52 0>;
> +      dma-names = "rxtx";
> +      clocks = <&l3s_gclk>;
> +      clock-names = "fck";
> +      reg = <0x50000000 0x2000>;
> +      interrupts = <GIC_SPI 100 IRQ_TYPE_LEVEL_HIGH>;
> +      gpmc,num-cs = <7>;
> +      gpmc,num-waitpins = <2>;
> +      #address-cells = <2>;
> +      #size-cells = <1>;
> +      interrupt-controller;
> +      #interrupt-cells = <2>;
> +      gpio-controller;
> +      #gpio-cells = <2>;
> +
> +      ranges = <0 0 0x08000000 0x01000000>;   /* CS0 space. Min partition = 16MB */
> +      nand@0,0 {
> +        compatible = "ti,omap2-nand";
> +        reg = <0 0 4>;          /* device IO registers */
> +        interrupt-parent = <&gpmc>;
> +        interrupts = <0 IRQ_TYPE_NONE>, /* fifoevent */
> +                     <1 IRQ_TYPE_NONE>; /* termcount */
> +        ti,nand-xfer-type = "prefetch-dma";
> +        ti,nand-ecc-opt = "bch16";
> +        ti,elm-id = <&elm>;
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +
> +        /* NAND generic properties */
> +        nand-bus-width = <8>;
> +        rb-gpios = <&gpmc 0 GPIO_ACTIVE_HIGH>;  /* gpmc_wait0 */
> +
> +        /* GPMC properties*/
> +        gpmc,device-width = <1>;
> +      };
> +    };


Thanks,
Miquèl