[Letux-kernel] [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module

H. Nikolaus Schaller hns at goldelico.com
Fri Jun 23 20:59:28 CEST 2017

Hi Suman,

> Am 23.06.2017 um 20:05 schrieb Suman Anna <s-anna at ti.com>:
>>>> Or does it just mean that it defines the property name?
>>> Please read the documentation link I sent - it's in the very bottom and
>>> should have an example.
>> I have seen it but it does not give me a good clue how to translate that into
>> correct omap3isp node setup in a specific DT. Rather it raises more questions.
>> Maybe because I don't understand completely what it is talking about.
>> The fundamental question is if this "assigned-clock-rates" is already
>> handled by ov965x->clk = devm_clk_get(&client->dev, NULL); ?
>> Or should we define that for the omap3isp node?
>> Then of course we need no new code and just use the right property names.
>> And N900, N9 camera DTs should be updated.
> Look up of_clk_set_defaults() function in drivers/clk/clk-conf.c. This
> function gets invoked usually during clock registration, and also gets
> called in platform_drv_probe(), so the parents and clocks do get
> configured before your driver gets probed. So, this provides a default
> configuration if these properties are supplied (in either clock nodes or
> actual device nodes), and if your driver needs to change the rates at
> runtime, then you would have to do that in the driver itself.

Ok, now I understand. Thanks!

Quite hidden, but nice feature. I would never have thought that it exists.
Especially as there are no examples around omap3isp cameras...

And an fgrep assigned-clock-rates shows not many use cases outside CPU/SoC
include files.

But interestingly arch/arm/boot/dts/at91sam9g25ek.dts uses it for an ovti,ov2640 camera...

So it seems that we just have to write:

	ov9655 at 30 {
		compatible = "ovti,ov9655";
		reg = <0x30>;
		clocks = <&isp 0>;	/* cam_clka */
		assigned-clocks = <&isp 0>;
		assigned-clock-rates = <24000000>;

instead of introducing a new clock-frequency property and code to handle it.

Or do I misinterpret what "parents" and "clocks" are in this context?

BR and thanks,

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