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

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Message-ID: <20200319124452.3yfcvq754vi4q2rv@gilmour.lan>
Date:   Thu, 19 Mar 2020 13:44:52 +0100
From:   Maxime Ripard <maxime@...no.tech>
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>,
        Laurent Pinchart <laurent.pinchart@...asonboard.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,

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.
>
> 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.
>  - 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>;

clock-frequency is quite different from assigned-clock-rates though,
semantically speaking. clock-frequency is only about what the clock
frequency is, while assigned-clock-rates will change the rate as well,
and you have no idea how long it will last.

If you want to retrieve that through the clock framework, then just
making clock-frequency optional is enough and falling back to
clk_get_rate on the clocks property already provided is enough.

Maxime

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