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Date:   Mon, 11 May 2020 11:09:24 -0500
From:   Rob Herring <robh@kernel.org>
To:     Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc:     Jarkko Nikula <jarkko.nikula@linux.intel.com>,
        Serge Semin <fancer.lancer@gmail.com>,
        Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Paul Burton <paulburton@kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Frank Rowand <frowand.list@gmail.com>,
        linux-mips@vger.kernel.org, linux-i2c@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 02/12] dt-bindings: i2c: Convert DW I2C binding to DT
 schema
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On Sun, May 10, 2020 at 12:50:08PM +0300, Serge Semin wrote:
> Modern device tree bindings are supposed to be created as YAML-files
> in accordance with dt-schema. This commit replaces Synopsys DW I2C
> legacy bare text bindings with YAML file. As before the bindings file
> states that the corresponding dts node is supposed to be compatible
> either with generic DW I2C controller or with Microsemi Ocelot SoC I2C
> one, to have registers, interrupts and clocks properties. In addition
> the node may have clock-frequency, i2c-sda-hold-time-ns,
> i2c-scl-falling-time-ns and i2c-sda-falling-time-ns optional properties.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Paul Burton <paulburton@kernel.org>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: Frank Rowand <frowand.list@gmail.com>
> Cc: linux-mips@vger.kernel.org
> 
> ---
> 
> Changelog v2:
> - Make sure that "mscc,ocelot-i2c" compatible node may have up to two
>   registers space defined, while normal DW I2C controller will have only
>   one registers space.
> - Add "mscc,ocelot-i2c" example to test the previous fix.
> - Declare "unevaluatedProperties" property instead of
>   "additionalProperties" one.
> - Due to the previous fix we can now discard the dummy boolean properties
>   definitions, since the proper type evaluation will be performed by the
>   generic i2c-controller.yaml schema.
> ---
>  .../bindings/i2c/i2c-designware.txt           |  73 ---------
>  .../bindings/i2c/snps,designware-i2c.yaml     | 154 ++++++++++++++++++
>  2 files changed, 154 insertions(+), 73 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/i2c/i2c-designware.txt
>  create mode 100644 Documentation/devicetree/bindings/i2c/snps,designware-i2c.yaml
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> deleted file mode 100644
> index 08be4d3846e5..000000000000
> --- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> +++ /dev/null
> @@ -1,73 +0,0 @@
> -* Synopsys DesignWare I2C
> -
> -Required properties :
> -
> - - compatible : should be "snps,designware-i2c"
> -                or "mscc,ocelot-i2c" with "snps,designware-i2c" for fallback
> - - reg : Offset and length of the register set for the device
> - - interrupts : <IRQ> where IRQ is the interrupt number.
> - - clocks : phandles for the clocks, see the description of clock-names below.
> -   The phandle for the "ic_clk" clock is required. The phandle for the "pclk"
> -   clock is optional. If a single clock is specified but no clock-name, it is
> -   the "ic_clk" clock. If both clocks are listed, the "ic_clk" must be first.
> -
> -Recommended properties :
> -
> - - clock-frequency : desired I2C bus clock frequency in Hz.
> -
> -Optional properties :
> -
> - - clock-names : Contains the names of the clocks:
> -    "ic_clk", for the core clock used to generate the external I2C clock.
> -    "pclk", the interface clock, required for register access.
> -
> - - reg : for "mscc,ocelot-i2c", a second register set to configure the SDA hold
> -   time, named ICPU_CFG:TWI_DELAY in the datasheet.
> -
> - - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
> -   This option is only supported in hardware blocks version 1.11a or newer and
> -   on Microsemi SoCs ("mscc,ocelot-i2c" compatible).
> -
> - - i2c-scl-falling-time-ns : should contain the SCL falling time in nanoseconds.
> -   This value which is by default 300ns is used to compute the tLOW period.
> -
> - - i2c-sda-falling-time-ns : should contain the SDA falling time in nanoseconds.
> -   This value which is by default 300ns is used to compute the tHIGH period.
> -
> -Examples :
> -
> -	i2c@f0000 {
> -		#address-cells = <1>;
> -		#size-cells = <0>;
> -		compatible = "snps,designware-i2c";
> -		reg = <0xf0000 0x1000>;
> -		interrupts = <11>;
> -		clock-frequency = <400000>;
> -	};
> -
> -	i2c@1120000 {
> -		#address-cells = <1>;
> -		#size-cells = <0>;
> -		compatible = "snps,designware-i2c";
> -		reg = <0x1120000 0x1000>;
> -		interrupt-parent = <&ictl>;
> -		interrupts = <12 1>;
> -		clock-frequency = <400000>;
> -		i2c-sda-hold-time-ns = <300>;
> -		i2c-sda-falling-time-ns = <300>;
> -		i2c-scl-falling-time-ns = <300>;
> -	};
> -
> -	i2c@1120000 {
> -		#address-cells = <1>;
> -		#size-cells = <0>;
> -		reg = <0x2000 0x100>;
> -		clock-frequency = <400000>;
> -		clocks = <&i2cclk>;
> -		interrupts = <0>;
> -
> -		eeprom@64 {
> -			compatible = "linux,slave-24c02";
> -			reg = <0x40000064>;
> -		};
> -	};
> diff --git a/Documentation/devicetree/bindings/i2c/snps,designware-i2c.yaml b/Documentation/devicetree/bindings/i2c/snps,designware-i2c.yaml
> new file mode 100644
> index 000000000000..8d4e5fccbd1c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/snps,designware-i2c.yaml
> @@ -0,0 +1,154 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/i2c/snps,designware-i2c.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Synopsys DesignWare APB I2C Controller
> +
> +maintainers:
> +  - Jarkko Nikula <jarkko.nikula@linux.intel.com>
> +
> +allOf:
> +  - $ref: /schemas/i2c/i2c-controller.yaml#
> +  - if:
> +      properties:
> +        compatible:
> +          not:
> +            contains:
> +              const: mscc,ocelot-i2c
> +    then:
> +      properties:
> +        reg:
> +          maxItems: 1
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - description: Generic Synopsys DesignWare I2C controller
> +        const: snps,designware-i2c
> +      - description: Microsemi Ocelot SoCs I2C controller
> +        items:
> +          - const: mscc,ocelot-i2c
> +          - const: snps,designware-i2c
> +
> +  reg:
> +    minItems: 1
> +    items:
> +      - description: DW APB I2C controller memory mapped registers
> +      - description: |
> +          ICPU_CFG:TWI_DELAY registers to setup the SDA hold time.
> +          This registers are specific to the Ocelot I2C-controller.
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clocks:
> +    minItems: 1
> +    items:
> +      - description: I2C controller reference clock source
> +      - description: APB interface clock source
> +
> +  clock-names:
> +    minItems: 1
> +    items:
> +      - const: ref
> +      - const: pclk
> +
> +  resets:
> +    maxItems: 1
> +
> +  clock-frequency:
> +    description: Desired I2C bus clock frequency in Hz
> +    enum: [100000, 400000, 1000000, 3400000]
> +    default: 400000
> +
> +  i2c-sda-hold-time-ns:
> +    $ref: /schemas/types.yaml#/definitions/uint32

Don't need a type ref as properties with a unit-suffix already have one.

> +    description: |
> +      The property should contain the SDA hold time in nanoseconds. This option
> +      is only supported in hardware blocks version 1.11a or newer or on
> +      Microsemi SoCs.
> +
> +  i2c-scl-falling-time-ns:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      The property should contain the SCL falling time in nanoseconds.
> +      This value is used to compute the tLOW period.
> +    default: 300
> +
> +  i2c-sda-falling-time-ns:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      The property should contain the SDA falling time in nanoseconds.
> +      This value is used to compute the tHIGH period.
> +    default: 300
> +
> +  dmas:
> +    items:
> +      - description: TX DMA Channel
> +      - description: RX DMA Channel
> +
> +  dma-names:
> +    items:
> +      - const: tx
> +      - const: rx
> +
> +unevaluatedProperties: false
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#address-cells"
> +  - "#size-cells"
> +  - interrupts
> +
> +examples:
> +  - |
> +    i2c@f0000 {
> +      compatible = "snps,designware-i2c";
> +      reg = <0xf0000 0x1000>;
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      interrupts = <11>;
> +      clock-frequency = <400000>;
> +    };
> +  - |
> +    i2c@1120000 {
> +      compatible = "snps,designware-i2c";
> +      reg = <0x1120000 0x1000>;
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      interrupts = <12 1>;
> +      clock-frequency = <400000>;
> +      i2c-sda-hold-time-ns = <300>;
> +      i2c-sda-falling-time-ns = <300>;
> +      i2c-scl-falling-time-ns = <300>;
> +    };
> +  - |
> +    i2c@2000 {
> +      compatible = "snps,designware-i2c";
> +      reg = <0x2000 0x100>;
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      clock-frequency = <400000>;
> +      clocks = <&i2cclk>;
> +      interrupts = <0>;
> +
> +      eeprom@64 {
> +        compatible = "linux,slave-24c02";
> +        reg = <0x40000064>;

This causes 'make dt_binding_check' to fail. The unit-address should be 
'40000064'. However, there's a bug in dtc not liking the high bits set 
either. There's a fix pending, but I'd just fix the example here to 
avoid the issue. 

> +      };
> +    };
> +  - |
> +    i2c@100400 {
> +      compatible = "mscc,ocelot-i2c", "snps,designware-i2c";
> +      reg = <0x100400 0x100>, <0x198 0x8>;
> +      pinctrl-0 = <&i2c_pins>;
> +      pinctrl-names = "default";
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      interrupts = <8>;
> +      clocks = <&ahb_clk>;
> +    };
> +...
> -- 
> 2.25.1
>