linux-kernel - Re: [PATCH 04/11] MFD: twl4030-audio: Add DT support

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Date:	Wed, 08 Aug 2012 15:43:29 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Benoit Cousson <b-cousson@...com>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, Tony Lindgren <tony@...mide.com>,
	Dmitry Torokhov <dtor@...l.ru>, alsa-devel@...a-project.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org
Subject: Re: [PATCH 04/11] MFD: twl4030-audio: Add DT support

Hi Benoit,

On 08/08/2012 02:50 PM, Benoit Cousson wrote:
>> +Required properties:
>> +- compatible : must be "ti,twl4030-audio"
>> +- ti,audio_mclk: Master clock frequency used on the board. Supported
>> +	         frequencies: 19200000, 26000000 and 38400000
> 
> Since you care about the frequency only you can use the generic
> attribute: clock-frequency (in your example, I2C is using it).

I see, I'll use replace the property with clock-frequency.

> That being said, since we do have the clock binding now, maybe we should
> create a clock provider at board level for the sys_clk and thus you will
> just have to create a phandle to it in your audio description.
> 
> In theory OMAP and other components will thus have to use that sys_clock
> reference as well.

And in the driver I would need to do for example:
clkp = clk_get(NULL, "audio_mclk");
clk_rate = clk_get_rate(clkp);
clk_put(clkp);

to get the frequency in this way?
Note that the twl4030-audio stack itself does not handle clocks at the moment
since the clock needed for the audio module is always running (HFCLKIN ->
HFCLKOUT -> AUDIO_MCLK (USB_MCLK)). All of this is within twl4030. Do we
really want to model this?

-- 
Péter
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