linux-kernel - Re: [PATCH v5 1/4] dt-bindings: media: imx258: add bindings for IMX258 sensor

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Date:   Tue, 20 Oct 2020 13:38:33 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org
Subject: Re: [PATCH v5 1/4] dt-bindings: media: imx258: add bindings for
 IMX258 sensor

Hi Krzysztof,

On Mon, Oct 19, 2020 at 07:02:44PM +0200, Krzysztof Kozlowski wrote:
> Add bindings for the IMX258 camera sensor.  The bindings, just like the
> driver, are quite limited, e.g. do not support regulator supplies.
> 
> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> Reviewed-by: Rob Herring <robh@...nel.org>
> 
> ---
> 
> Changes since v4:
> 1. Add clock-lanes,
> 2. Add Rob's review,
> 3. Add one more example and extend existing one,
> 4. Add common clock properties (assigned-*).

Using the assigned-* clock properties may be workable for this driver at
the moment. But using these properties does not guarantee the external
clock frequency intended to be used on the hardware. Using other
frequencies *is not* expected to work. That applies to this driver as well.

This, instead of the clock-frequency property, effectively removes the
ability to set the correct frequency from the driver, at least with current
set of the used APIs.

I suppose you could add a function to set the assigned clock frequency and
keep it, just as clk_set_rate_exclusive does?

Cc the common clock framework list + maintainers.

-- 
Regards,

Sakari Ailus