linux-kernel - Re: [alsa-devel] [PATCH] ASoC: rt5640: add master clock handling for rt5640

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Date:	Tue, 23 Feb 2016 08:50:04 -0600
From:	Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:	Sugar Zhang <sugar.zhang@...k-chips.com>, broonie@...nel.org,
	heiko@...ech.de
Cc:	Mark Rutland <mark.rutland@....com>,
	Oder Chiou <oder_chiou@...ltek.com>,
	alsa-devel@...a-project.org, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	linux-kernel@...r.kernel.org, Takashi Iwai <tiwai@...e.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Bard Liao <bardliao@...ltek.com>
Subject: Re: [alsa-devel] [PATCH] ASoC: rt5640: add master clock handling for
 rt5640

On 2/22/16 7:26 PM, Sugar Zhang wrote:
> enable/disable master clock when codec is active or not.
>
> Signed-off-by: Sugar Zhang <sugar.zhang@...k-chips.com>
> ---
>
>   Documentation/devicetree/bindings/sound/rt5640.txt |  3 +++
>   sound/soc/codecs/rt5640.c                          | 31 ++++++++++++++++++++++
>   sound/soc/codecs/rt5640.h                          |  2 ++
>   3 files changed, 36 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/sound/rt5640.txt b/Documentation/devicetree/bindings/sound/rt5640.txt
> index 9e62f6e..57fe646 100644
> --- a/Documentation/devicetree/bindings/sound/rt5640.txt
> +++ b/Documentation/devicetree/bindings/sound/rt5640.txt
> @@ -12,6 +12,9 @@ Required properties:
>
>   Optional properties:
>
> +- clocks: The phandle of the master clock to the CODEC
> +- clock-names: Should be "mclk"

This patch assumes that the information on mclk comes from DeviceTree. 
The mclk may also be enabled/disabled in the machine driver with an 
explicit transition to use an internal clock when the codec is not used.
I hope this patch doesn't preclude such usages or there will be a 
conflict with the patches we are about to upstream for Baytrail/cht devices.

> +
>   - realtek,in1-differential
>   - realtek,in2-differential
>   - realtek,in3-differential
> diff --git a/sound/soc/codecs/rt5640.c b/sound/soc/codecs/rt5640.c
> index 11d032c..6cd84fb 100644
> --- a/sound/soc/codecs/rt5640.c
> +++ b/sound/soc/codecs/rt5640.c
> @@ -1949,7 +1949,33 @@ static int rt5640_set_dai_pll(struct snd_soc_dai *dai, int pll_id, int source,
>   static int rt5640_set_bias_level(struct snd_soc_codec *codec,
>   			enum snd_soc_bias_level level)
>   {
> +	struct rt5640_priv *rt5640 = snd_soc_codec_get_drvdata(codec);
> +	int ret;
> +
>   	switch (level) {
> +	case SND_SOC_BIAS_ON:
> +		break;
> +
> +	case SND_SOC_BIAS_PREPARE:
> +		/*
> +		 * SND_SOC_BIAS_PREPARE is called while preparing for a
> +		 * transition to ON or away from ON. If current bias_level
> +		 * is SND_SOC_BIAS_ON, then it is preparing for a transition
> +		 * away from ON. Disable the clock in that case, otherwise
> +		 * enable it.
> +		 */
> +		if (IS_ERR(rt5640->mclk))
> +			break;
> +
> +		if (snd_soc_codec_get_bias_level(codec) == SND_SOC_BIAS_ON) {
> +			clk_disable_unprepare(rt5640->mclk);
> +		} else {
> +			ret = clk_prepare_enable(rt5640->mclk);
> +			if (ret)
> +				return ret;
> +		}
> +		break;
> +
>   	case SND_SOC_BIAS_STANDBY:
>   		if (SND_SOC_BIAS_OFF == snd_soc_codec_get_bias_level(codec)) {
>   			snd_soc_update_bits(codec, RT5640_PWR_ANLG1,
> @@ -2088,6 +2114,11 @@ static int rt5640_probe(struct snd_soc_codec *codec)
>   	struct snd_soc_dapm_context *dapm = snd_soc_codec_get_dapm(codec);
>   	struct rt5640_priv *rt5640 = snd_soc_codec_get_drvdata(codec);
>
> +	/* Check if MCLK provided */
> +	rt5640->mclk = devm_clk_get(codec->dev, "mclk");
> +	if (PTR_ERR(rt5640->mclk) == -EPROBE_DEFER)
> +		return -EPROBE_DEFER;
> +
>   	rt5640->codec = codec;
>
>   	snd_soc_codec_force_bias_level(codec, SND_SOC_BIAS_OFF);
> diff --git a/sound/soc/codecs/rt5640.h b/sound/soc/codecs/rt5640.h
> index 83a7150..1761c3a9 100644
> --- a/sound/soc/codecs/rt5640.h
> +++ b/sound/soc/codecs/rt5640.h
> @@ -12,6 +12,7 @@
>   #ifndef _RT5640_H
>   #define _RT5640_H
>
> +#include <linux/clk.h>
>   #include <sound/rt5640.h>
>
>   /* Info */
> @@ -2097,6 +2098,7 @@ struct rt5640_priv {
>   	struct snd_soc_codec *codec;
>   	struct rt5640_platform_data pdata;
>   	struct regmap *regmap;
> +	struct clk *mclk;
>
>   	int sysclk;
>   	int sysclk_src;
>