Question about fixed-clock

Daniel Mack
2013-02-19T09:53:18Z

Hi Fabio,
Hi Afzal,

On 19.02.2013 02:33, Fabio Estevam wrote:
> On Mon, Feb 18, 2013 at 8:55 PM, Daniel Mack <zonque@gmail.com> wrote:
>> Hi,
>>
>> This might be a stupid question, but I'm somehow stuck here. I'm using a
>> driver with the following DTS sub-node:
>>
>> ref25: ref25M {
>> compatible = "fixed-clock";
>> #clock-cells = <0>;
>> clock-frequency = <25000000>;
>> };
>>
>> clock-generator at 0 {
>> /* ... */
>> #clock-cells = <1>;
>> clocks = <&ref25>;
>> }
>>
>> The device driver for clock-generator uses something like the following
>> call to get its clock:
>>
>> clk = of_clk_get(np, 0);
>>
>> but the return value is ERR_PTR(-ENOENT) and I also can't find this
>> clock in the clk debugfs tree.
>>
>> This is on a OMAP/AM33xx device with kernel 3.8-rc7 plus the -next tips
>> of arm-soc and omap, but with no other special clock options selected in
>> the config. Is there anything I'm missing to correctly instantiate the
>> dummy clock?
>
> Have you registered it with clk_register_fixed_rate() ?
>
> In imx we use imx_clk_fixed, which in turns call clk_register_fixed_rate().
>
> Take a look at arch/arm/mach-imx/clk-imx51-imx53.c for a reference.

Hmm no, I didn't do anything else than adding it to the DT in the first
place, hoping that a driver will pick it up and add the clock for me.
But it turns out that of_clk_init() is not called at all on my platform.

I'm doing this now from omap_generic_init() and it works. If that's an
appropriate place to call it, I can provide a patch.

Thanks,
Daniel