linux-kernel - Re: Question about fixed-clock

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Date:	Mon, 18 Feb 2013 22:33:48 -0300
From:	Fabio Estevam <festevam@...il.com>
To:	Daniel Mack <zonque@...il.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Question about fixed-clock

Hi Daniel,

On Mon, Feb 18, 2013 at 8:55 PM, Daniel Mack <zonque@...il.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@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.
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