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Date:   Fri, 24 Mar 2023 12:13:29 -0500
From:   Rob Herring <robh@kernel.org>
To:     Dipen Patel <dipenp@nvidia.com>
Cc:     thierry.reding@gmail.com, jonathanh@nvidia.com,
        linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-gpio@vger.kernel.org, linus.walleij@linaro.org,
        devicetree@vger.kernel.org, linux-doc@vger.kernel.org,
        timestamp@lists.linux.dev, krzysztof.kozlowski+dt@linaro.org,
        brgl@bgdev.pl, corbet@lwn.net, gregkh@linuxfoundation.org
Subject: Re: [PATCH V4 04/10] dt-bindings: timestamp: Add
 nvidia,gpio-controller
Message-ID: <20230324171329.GA2062332-robh@kernel.org>
References: <20230323012929.10815-1-dipenp@nvidia.com>
 <20230323012929.10815-5-dipenp@nvidia.com>
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On Wed, Mar 22, 2023 at 06:29:23PM -0700, Dipen Patel wrote:
> Introducing nvidia,gpio-controller property from Tegra234 SoCs onwards.
> This is done to help below case.
> 
> Without this property code would look like:
> if (of_device_is_compatible(dev->of_node, "nvidia,tegra194-gte-aon"))
> 	hte_dev->c = gpiochip_find("tegra194-gpio-aon",
> 				   tegra_get_gpiochip_from_name);
> else if (of_device_is_compatible(dev->of_node, "nvidia,tegra234-gte-aon"))
> 	hte_dev->c = gpiochip_find("tegra234-gpio-aon",
> 				   tegra_get_gpiochip_from_name);
> else
> 	return -ENODEV;

Or you just put the name in match data.

> 
> This means for every future addition of the compatible string, if else
> condition statements have to be expanded.
> 
> With the property:
> gpio_ctrl = of_parse_phandle(dev->of_node, "nvidia,gpio-controller", 0);
> ....
> hte_dev->c = gpiochip_find(gpio_ctrl, tegra_get_gpiochip_from_of_node);
> 
> This simplifies the code significantly. The introdunction of this

typo 

> property/binding does not break existing Tegra194 provider driver.

Making a new property required is an ABI break.

> Signed-off-by: Dipen Patel <dipenp@nvidia.com>
> ---
>  .../timestamp/nvidia,tegra194-hte.yaml        | 31 +++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml b/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> index eafc33e9ae2e..841273a3d8ae 100644
> --- a/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> +++ b/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> @@ -51,6 +51,12 @@ properties:
>        LIC instance has 11 slices and Tegra234 LIC has 17 slices.
>      enum: [3, 11, 17]
>  
> +  nvidia,gpio-controller:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      The phandle to AON gpio controller instance. This is required to handle
> +      namespace conversion between GPIO and GTE.

Explain what the GPIO controller is needed for rather than how this 
changes the driver.

> +
>    '#timestamp-cells':
>      description:
>        This represents number of line id arguments as specified by the
> @@ -65,22 +71,43 @@ required:
>    - interrupts
>    - "#timestamp-cells"
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - nvidia,tegra234-gte-aon
> +    then:
> +      required:
> +        - nvidia,gpio-controller

> +
>  additionalProperties: false
>  
>  examples:
>    - |
>      tegra_hte_aon: timestamp@c1e0000 {
>                compatible = "nvidia,tegra194-gte-aon";
> -              reg = <0xc1e0000 0x10000>;
> +              reg = <0x0 0xc1e0000 0x0 0x10000>;
> +              interrupts = <0 13 0x4>;
> +              nvidia,int-threshold = <1>;
> +              #timestamp-cells = <1>;
> +    };
> +
> +  - |
> +    tegra234_hte_aon: timestamp@c1e0000 {
> +              compatible = "nvidia,tegra234-gte-aon";
> +              reg = <0x0 0xc1e0000 0x0 0x10000>;
>                interrupts = <0 13 0x4>;
>                nvidia,int-threshold = <1>;
> +              nvidia,gpio-controller = <&gpio_aon>;
>                #timestamp-cells = <1>;
>      };
>  
>    - |
>      tegra_hte_lic: timestamp@3aa0000 {
>                compatible = "nvidia,tegra194-gte-lic";
> -              reg = <0x3aa0000 0x10000>;
> +              reg = <0x0 0x3aa0000 0x0 0x10000>;
>                interrupts = <0 11 0x4>;
>                nvidia,int-threshold = <1>;
>                #timestamp-cells = <1>;
> -- 
> 2.17.1
>