linux-kernel - Re: [RFC V2 1/2] ASoC: img: Add binding document for Pistachio audio card

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Date:	Wed, 27 Jan 2016 20:14:57 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Damien Horsley <Damien.Horsley@...tec.com>
Cc:	alsa-devel@...a-project.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	James Hartley <james.hartley@...tec.com>
Subject: Re: [RFC V2 1/2] ASoC: img: Add binding document for Pistachio audio
 card

On Wed, Jan 27, 2016 at 05:13:09PM +0000, Damien Horsley wrote:

> audio_pll is referenced exclusively by the card device

That one *may* be plausible.

> i2s_mclk and dac_mclk can also be referenced by other devices. The i2s
> out controller references i2s_mclk, and codec devices can reference
> i2s_mclk/dac_mclk dependent on their system clock requirements

The clock API copes perfectly happily with this.

> without a reference to i2s_mclk and dac_mclk in the card driver, it
> would not be possible to control the divisors and gates for these clocks
> in the following cases:

> Simplistic codecs that do not have drivers

> Codec drivers that do not call clk_set_rate and clk_enable/clk_disable

Nonsense, if there is no driver or the driver doesn't do what you want
then fix that.  Don't bodge things at the wrong abstraction layer, that
just creates problems later on when someone comes along and does things
properly or tries to use the device tree outside of your particular
implementation (eg, when working with a differnet OS).

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