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

Suman Anna s-anna at ti.com
Sat Jun 24 00:24:26 CEST 2017

On 06/23/2017 01:59 PM, H. Nikolaus Schaller wrote:
> 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>;
> 	};

Yeah, that looks alright and should work.


> 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?

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