linux-kernel - Re: [PATCH v3 1/4] media: dt-bindings: media: i2c: Switch to assigned-clock-rates

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Date:   Fri, 13 Mar 2020 23:20:12 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        NXP Linux Team <linux-imx@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Fabio Estevam <festevam@...il.com>,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/4] media: dt-bindings: media: i2c: Switch to
 assigned-clock-rates

Hi Prabhakar,

Thank you for the patch.

On Fri, Mar 13, 2020 at 09:12:31PM +0000, Lad Prabhakar wrote:
> Use assigned-clock-rates to specify the clock rate. Also mark
> clock-frequency property as deprecated.

I would phrase it the other way around, this patch mainly deprecates
clock-frequency, and as a side effect recommends usage of
assigned-clock-rates.

"Deprecate usage of the clock-frequency propertly. The preferred method
to set clock rates is to use assigned-clock-rates."

> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
>  Documentation/devicetree/bindings/media/i2c/ov5645.txt | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ov5645.txt b/Documentation/devicetree/bindings/media/i2c/ov5645.txt
> index 72ad992..e62fe82 100644
> --- a/Documentation/devicetree/bindings/media/i2c/ov5645.txt
> +++ b/Documentation/devicetree/bindings/media/i2c/ov5645.txt
> @@ -8,7 +8,7 @@ Required Properties:
>  - compatible: Value should be "ovti,ov5645".
>  - clocks: Reference to the xclk clock.
>  - clock-names: Should be "xclk".
> -- clock-frequency: Frequency of the xclk clock.
> +- clock-frequency (deprecated): Frequency of the xclk clock.

I would drop this completely. Drivers need to ensure backward
compatibility, but DT bindings should only document the latest version,
the history is available in git.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

While at it, can I enlist you to convert these bindings to yaml ? :-)

>  - enable-gpios: Chip enable GPIO. Polarity is GPIO_ACTIVE_HIGH. This corresponds
>    to the hardware pin PWDNB which is physically active low.
>  - reset-gpios: Chip reset GPIO. Polarity is GPIO_ACTIVE_LOW. This corresponds to
> @@ -37,7 +37,8 @@ Example:
>  
>  			clocks = <&clks 200>;
>  			clock-names = "xclk";
> -			clock-frequency = <24000000>;
> +			assigned-clocks = <&clks 200>;
> +			assigned-clock-rates = <24000000>;
>  
>  			vdddo-supply = <&camera_dovdd_1v8>;
>  			vdda-supply = <&camera_avdd_2v8>;

-- 
Regards,

Laurent Pinchart