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Date:   Tue, 15 Jan 2019 22:18:02 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Cheng-Yi Chiang <cychiang@chromium.org>
Cc:     linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
        tzungbi@chromium.org, Benson Leung <bleung@chromium.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Brown <broonie@kernel.org>,
        Rohit kumar <rohitkr@codeaurora.org>,
        Guenter Roeck <groeck@chromium.org>, dgreid@chromium.org,
        Lee Jones <lee.jones@linaro.org>
Subject: Re: [alsa-devel] [PATCH v3 3/3] ASoC: cros_ec_codec: Add codec
 driver for Cros EC
Message-ID: <20190116061802.GA31405@roeck-us.net>
References: <20181226070317.72022-1-cychiang@chromium.org>
 <20181226070317.72022-3-cychiang@chromium.org>
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In-Reply-To: <20181226070317.72022-3-cychiang@chromium.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Wed, Dec 26, 2018 at 03:03:19PM +0800, Cheng-Yi Chiang wrote:
> Add a codec driver to control ChromeOS EC codec.
> 
> Use EC Host command to enable/disable I2S recording and control other
> configurations.
> 
> Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
> ---
> Changes in v3:
> 1.remove cros_ec_codec.h.
> 2.Fix error code overriding in
>     set_i2s_config
>     set_i2s_sample_depth
>     set_bclk
>     get_ec_mic_gain
>     set_ec_mic_gain
>     enable_i2s
> 3.Fix missing return code in cros_ec_i2s_set_dai_fmt.
> 4.Simplify return code in cros_ec_i2s_hw_params and mic_gain_put.
> 5.Remove useless debug message in cros_ec_codec_platform_probe.
> 
>  MAINTAINERS                      |   2 +
>  sound/soc/codecs/Kconfig         |   8 +
>  sound/soc/codecs/Makefile        |   2 +
>  sound/soc/codecs/cros_ec_codec.c | 454 +++++++++++++++++++++++++++++++
>  4 files changed, 466 insertions(+)
>  create mode 100644 sound/soc/codecs/cros_ec_codec.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 05e1922624e58..d66f80f3252d7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3638,8 +3638,10 @@ F:	drivers/platform/chrome/
>  
>  CHROMEOS EC CODEC DRIVER
>  M:	Cheng-Yi Chiang <cychiang@chromium.org>
> +R:	Enric Balletbo i Serra <enric.balletbo@collabora.com>
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/sound/google,cros-ec-codec.txt
> +F:	sound/soc/codecs/cros_ec_codec.*
>  
>  CIRRUS LOGIC AUDIO CODEC DRIVERS
>  M:	Brian Austin <brian.austin@cirrus.com>
> diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
> index 87cb9c51e6f5a..0b36428159b71 100644
> --- a/sound/soc/codecs/Kconfig
> +++ b/sound/soc/codecs/Kconfig
> @@ -50,6 +50,7 @@ config SND_SOC_ALL_CODECS
>  	select SND_SOC_BT_SCO
>  	select SND_SOC_BD28623
>  	select SND_SOC_CQ0093VC
> +	select SND_SOC_CROS_EC_CODEC

This unconditionally selects SND_SOC_CROS_EC_CODEC, but SND_SOC_CROS_EC_CODEC
depends on MFD_CROS_EC. This is missing an "if MFD_CROS_EC" qualifier.

>  	select SND_SOC_CS35L32 if I2C
>  	select SND_SOC_CS35L33 if I2C
>  	select SND_SOC_CS35L34 if I2C
> @@ -457,6 +458,13 @@ config SND_SOC_CPCAP
>  config SND_SOC_CQ0093VC
>  	tristate
>  
> +config SND_SOC_CROS_EC_CODEC
> +	tristate "codec driver for ChromeOS EC"
> +	depends on MFD_CROS_EC
> +	help
> +	  If you say yes here you will get support for the
> +	  ChromeOS Embedded Controller's Audio Codec.
> +
>  config SND_SOC_CS35L32
>  	tristate "Cirrus Logic CS35L32 CODEC"
>  	depends on I2C
> diff --git a/sound/soc/codecs/Makefile b/sound/soc/codecs/Makefile
> index 9bb3346fab2fe..3cfd8f5f61705 100644
> --- a/sound/soc/codecs/Makefile
> +++ b/sound/soc/codecs/Makefile
> @@ -42,6 +42,7 @@ snd-soc-bd28623-objs := bd28623.o
>  snd-soc-bt-sco-objs := bt-sco.o
>  snd-soc-cpcap-objs := cpcap.o
>  snd-soc-cq93vc-objs := cq93vc.o
> +snd-soc-cros-ec-codec-objs := cros_ec_codec.o
>  snd-soc-cs35l32-objs := cs35l32.o
>  snd-soc-cs35l33-objs := cs35l33.o
>  snd-soc-cs35l34-objs := cs35l34.o
> @@ -310,6 +311,7 @@ obj-$(CONFIG_SND_SOC_BD28623)	+= snd-soc-bd28623.o
>  obj-$(CONFIG_SND_SOC_BT_SCO)	+= snd-soc-bt-sco.o
>  obj-$(CONFIG_SND_SOC_CQ0093VC) += snd-soc-cq93vc.o
>  obj-$(CONFIG_SND_SOC_CPCAP)	+= snd-soc-cpcap.o
> +obj-$(CONFIG_SND_SOC_CROS_EC_CODEC)	+= snd-soc-cros-ec-codec.o
>  obj-$(CONFIG_SND_SOC_CS35L32)	+= snd-soc-cs35l32.o
>  obj-$(CONFIG_SND_SOC_CS35L33)	+= snd-soc-cs35l33.o
>  obj-$(CONFIG_SND_SOC_CS35L34)	+= snd-soc-cs35l34.o
> diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
> new file mode 100644
> index 0000000000000..85ea23f4b681c
> --- /dev/null
> +++ b/sound/soc/codecs/cros_ec_codec.c
> @@ -0,0 +1,454 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for ChromeOS Embedded Controller codec.
> + *
> + * This driver uses the cros-ec interface to communicate with the ChromeOS
> + * EC for audio function.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/mfd/cros_ec_commands.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <sound/pcm.h>
> +#include <sound/pcm_params.h>
> +#include <sound/soc.h>
> +#include <sound/tlv.h>
> +
> +#define MAX_GAIN 43

Is there some reason for this magic number ? What does it reflect ? 

> +
> +#define DRV_NAME "cros-ec-codec"
> +
> +/**
> + * struct cros_ec_codec_data - ChromeOS EC codec driver data.
> + * @dev:         Device structure used in sysfs.
> + * @ec_device:   cros_ec_device structure to talk to the physical device.
> + * @component:   Pointer to the component.
> + */
> +struct cros_ec_codec_data {
> +	struct device *dev;
> +	struct cros_ec_device *ec_device;
> +	struct snd_soc_component *component;
> +};
> +
> +static const DECLARE_TLV_DB_SCALE(ec_mic_gain_tlv, 0, 100, 0);
> +/*
> + * Wrapper for EC command.
> + */
> +static int ec_command(struct snd_soc_component *component, int version,
> +		      int command, u8 *outdata, int outsize,
> +		      u8 *indata, int insize)
> +{
> +	struct cros_ec_codec_data *codec_data =
> +		snd_soc_component_get_drvdata(component);
> +	struct cros_ec_device *ec_device = codec_data->ec_device;
> +	struct cros_ec_command *msg;
> +	int ret;
> +
> +	msg = kzalloc(sizeof(*msg) + max(insize, outsize), GFP_KERNEL);
> +	if (!msg)
> +		return -ENOMEM;

As far as I can see, the calling parameter is always "struct ec_param_codec_i2s".
With that in mind, this code seems unnecessarily complex. Is this code expected
to be called multiple times in parallel and requires multiple instances of
struct ec_param_codec_i2s to be allocated ? Even if so, why not just use
a local variable / array ?

[ This makes me wonder how EC transfers are synchronized in
  cros_ec_cmd_xfer_status() and below. Does anyone know ? I don't immedately
  see it.
]

> +
> +	msg->version = version;
> +	msg->command = command;
> +	msg->outsize = outsize;
> +	msg->insize = insize;
> +
> +	if (outsize)
> +		memcpy(msg->data, outdata, outsize);
> +
> +	ret = cros_ec_cmd_xfer_status(ec_device, msg);
> +	if (ret > 0 && insize)
> +		memcpy(indata, msg->data, insize);
> +
> +	kfree(msg);
> +	return ret;

I know this is wide-spread in cros_ec drivers, but that doesn't make it better.
The positive return value isn't used anywhere. On top of that, the called low
level code already generates error messages. As a result, the code calling this
function is unnecessarily complex. If the function was to return 0 for success
and a negative error code otherwise, pret much all all callers could be
simplified to

	return ec_command(...);

> +}
> +
> +static int set_i2s_config(struct snd_soc_component *component,
> +			  enum ec_i2s_config i2s_config)
> +{
> +	struct ec_param_codec_i2s param;
> +	int ret;
> +
> +	dev_dbg(component->dev, "%s set I2S format to %u\n", __func__,
> +		i2s_config);
> +
> +	param.cmd = EC_CODEC_I2S_SET_CONFIG;
> +	param.i2s_config = i2s_config;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 NULL, 0);
> +	if (ret < 0) {
> +		dev_err(component->dev,
> +			"set I2S format to %u command returned %d\n",
> +			i2s_config, ret);
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static int cros_ec_i2s_set_dai_fmt(struct snd_soc_dai *dai, unsigned int fmt)
> +{
> +	struct snd_soc_component *component = dai->component;
> +	enum ec_i2s_config i2s_config;
> +
> +	switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
> +	case SND_SOC_DAIFMT_CBS_CFS:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	switch (fmt & SND_SOC_DAIFMT_INV_MASK) {
> +	case SND_SOC_DAIFMT_NB_NF:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	switch (fmt & SND_SOC_DAIFMT_FORMAT_MASK) {
> +	case SND_SOC_DAIFMT_I2S:
> +		i2s_config = EC_DAI_FMT_I2S;
> +		break;
> +
> +	case SND_SOC_DAIFMT_RIGHT_J:
> +		i2s_config = EC_DAI_FMT_RIGHT_J;
> +		break;
> +
> +	case SND_SOC_DAIFMT_LEFT_J:
> +		i2s_config = EC_DAI_FMT_LEFT_J;
> +		break;
> +
> +	case SND_SOC_DAIFMT_DSP_A:
> +		i2s_config = EC_DAI_FMT_PCM_A;
> +		break;
> +
> +	case SND_SOC_DAIFMT_DSP_B:
> +		i2s_config = EC_DAI_FMT_PCM_B;
> +		break;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return set_i2s_config(component, i2s_config);
> +}
> +
> +static int set_i2s_sample_depth(struct snd_soc_component *component,
> +				enum ec_sample_depth_value depth)
> +{
> +	struct ec_param_codec_i2s param;
> +	int ret;
> +
> +	dev_dbg(component->dev, "%s set depth to %u\n", __func__, depth);
> +
> +	param.cmd = EC_CODEC_SET_SAMPLE_DEPTH;
> +	param.depth = depth;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 NULL, 0);
> +	if (ret < 0) {
> +		dev_err(component->dev, "I2S sample depth %u returned %d\n",
> +			depth, ret);
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static int set_bclk(struct snd_soc_component *component, uint32_t bclk)
> +{
> +	struct ec_param_codec_i2s param;
> +	int ret;
> +
> +	dev_dbg(component->dev, "%s set i2s bclk to %u\n", __func__, bclk);
> +
> +	param.cmd = EC_CODEC_I2S_SET_BCLK;
> +	param.bclk = bclk;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 NULL, 0);
> +	if (ret < 0) {
> +		dev_err(component->dev, "I2S set bclk %u command returned %d\n",
> +			bclk, ret);
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static int cros_ec_i2s_hw_params(struct snd_pcm_substream *substream,
> +				 struct snd_pcm_hw_params *params,
> +				 struct snd_soc_dai *dai)
> +{
> +	struct snd_soc_component *component = dai->component;
> +	int frame_size;
> +	unsigned int rate, bclk;
> +	int ret;
> +
> +	frame_size = snd_soc_params_to_frame_size(params);
> +	if (frame_size < 0) {
> +		dev_err(component->dev, "Unsupported frame size: %d\n",
> +			frame_size);
> +		return -EINVAL;
> +	}
> +
> +	rate = params_rate(params);
> +	if (rate != 48000) {
> +		dev_err(component->dev, "Unsupported rate\n");
> +		return -EINVAL;
> +	}
> +
> +	switch (params_format(params)) {
> +	case SNDRV_PCM_FORMAT_S16_LE:
> +		ret = set_i2s_sample_depth(component, EC_CODEC_SAMPLE_DEPTH_16);
> +		break;
> +	case SNDRV_PCM_FORMAT_S24_LE:
> +		ret = set_i2s_sample_depth(component, EC_CODEC_SAMPLE_DEPTH_24);
> +		break;
> +	default:
> +		return -EINVAL;

There is quite some inconsistency in error messages. Is there some kind of
plan behind it ? Do the error mesages above add value, but an error message
here wouldn't ?

> +	}
> +	if (ret < 0)
> +		return ret;
> +
> +	bclk = snd_soc_params_to_bclk(params);
> +	return set_bclk(component, bclk);
> +}
> +
> +static const struct snd_soc_dai_ops cros_ec_i2s_dai_ops = {
> +	.hw_params = cros_ec_i2s_hw_params,
> +	.set_fmt = cros_ec_i2s_set_dai_fmt,
> +};
> +
> +struct snd_soc_dai_driver cros_ec_dai[] = {
> +	{
> +		.name = "cros_ec_codec I2S",
> +		.id = 0,
> +		.capture = {
> +			.stream_name = "I2S Capture",
> +			.channels_min = 2,
> +			.channels_max = 2,
> +			.rates = SNDRV_PCM_RATE_48000,
> +			.formats = SNDRV_PCM_FMTBIT_S16_LE |
> +				   SNDRV_PCM_FMTBIT_S24_LE,
> +		},
> +		.ops = &cros_ec_i2s_dai_ops,
> +	}
> +};
> +
> +static int get_ec_mic_gain(struct snd_soc_component *component,
> +			   u8 *left, u8 *right)
> +{
> +	struct ec_param_codec_i2s param;
> +	struct ec_response_codec_gain resp;
> +	int ret;
> +
> +	param.cmd = EC_CODEC_GET_GAIN;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 (u8 *)&resp, sizeof(resp));
> +	if (ret < 0) {
> +		dev_err(component->dev, "I2S get gain command returned %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	*left = resp.left;
> +	*right = resp.right;
> +
> +	dev_dbg(component->dev, "%s get mic gain %u, %u\n", __func__,
> +		*left, *right);
> +
> +	return 0;
> +}
> +
> +static int mic_gain_get(struct snd_kcontrol *kcontrol,
> +			struct snd_ctl_elem_value *ucontrol)
> +{
> +	struct snd_soc_component *component =
> +		snd_soc_kcontrol_component(kcontrol);
> +	u8 left, right;
> +	int ret;
> +
> +	ret = get_ec_mic_gain(component, &left, &right);
> +	if (ret)
> +		return ret;
> +
> +	ucontrol->value.integer.value[0] = left;
> +	ucontrol->value.integer.value[1] = right;
> +
> +	return 0;
> +}
> +
> +static int set_ec_mic_gain(struct snd_soc_component *component,
> +			   u8 left, u8 right)
> +{
> +	struct ec_param_codec_i2s param;
> +	int ret;
> +
> +	dev_dbg(component->dev, "%s set mic gain to %u, %u\n",
> +		__func__, left, right);
> +
> +	param.cmd = EC_CODEC_SET_GAIN;
> +	param.gain.left = left;
> +	param.gain.right = right;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 NULL, 0);
> +	if (ret < 0) {
> +		dev_err(component->dev, "I2S set gain command returned %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mic_gain_put(struct snd_kcontrol *kcontrol,
> +			struct snd_ctl_elem_value *ucontrol)
> +{
> +	struct snd_soc_component *component =
> +		snd_soc_kcontrol_component(kcontrol);
> +	int left = ucontrol->value.integer.value[0];
> +	int right = ucontrol->value.integer.value[1];
> +
> +	if (left > MAX_GAIN || right > MAX_GAIN)
> +		return -EINVAL;
> +
> +	return set_ec_mic_gain(component, (u8)left, (u8)right);
> +}
> +
> +static const struct snd_kcontrol_new cros_ec_snd_controls[] = {
> +	SOC_DOUBLE_EXT_TLV("EC Mic Gain", SND_SOC_NOPM, SND_SOC_NOPM, 0, 43, 0,
> +			   mic_gain_get, mic_gain_put, ec_mic_gain_tlv)
> +};
> +
> +static int enable_i2s(struct snd_soc_component *component, int enable)
> +{
> +	struct ec_param_codec_i2s param;
> +	int ret;
> +
> +	dev_dbg(component->dev, "%s set i2s to %u\n", __func__, enable);
> +
> +	param.cmd = EC_CODEC_I2S_ENABLE;
> +	param.i2s_enable = enable;
> +
> +	ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> +			 (u8 *)&param, sizeof(param),
> +			 NULL, 0);
> +	if (ret < 0) {
> +		dev_err(component->dev, "I2S enable %d command returned %d\n",
> +			enable, ret);
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static int cros_ec_i2s_enable_event(struct snd_soc_dapm_widget *w,
> +				    struct snd_kcontrol *kcontrol, int event)
> +{
> +	struct snd_soc_component *component =
> +		snd_soc_dapm_to_component(w->dapm);
> +
> +	switch (event) {
> +	case SND_SOC_DAPM_PRE_PMU:
> +		dev_dbg(component->dev,
> +			"%s got SND_SOC_DAPM_PRE_PMU event\n", __func__);
> +		return enable_i2s(component, 1);
> +
> +	case SND_SOC_DAPM_PRE_PMD:
> +		dev_dbg(component->dev,
> +			"%s got SND_SOC_DAPM_PRE_PMD event\n", __func__);
> +		return enable_i2s(component, 0);
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * The goal of this DAPM route is to turn on/off I2S using EC
> + * host command when capture stream is started/stopped.
> + */
> +static const struct snd_soc_dapm_widget cros_ec_dapm_widgets[] = {
> +	SND_SOC_DAPM_INPUT("DMIC"),
> +
> +	/*
> +	 * Control EC to enable/disable I2S.
> +	 */
> +	SND_SOC_DAPM_SUPPLY("I2S Enable", SND_SOC_NOPM,
> +			    0, 0, cros_ec_i2s_enable_event,
> +			    SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_PRE_PMD),
> +
> +	SND_SOC_DAPM_AIF_OUT("I2STX", "I2S Capture", 0, SND_SOC_NOPM, 0, 0),
> +};
> +
> +static const struct snd_soc_dapm_route cros_ec_dapm_routes[] = {
> +	{ "I2STX", NULL, "DMIC" },
> +	{ "I2STX", NULL, "I2S Enable" },
> +};
> +
> +static const struct snd_soc_component_driver cros_ec_component_driver = {
> +	.controls		= cros_ec_snd_controls,
> +	.num_controls		= ARRAY_SIZE(cros_ec_snd_controls),
> +	.dapm_widgets		= cros_ec_dapm_widgets,
> +	.num_dapm_widgets	= ARRAY_SIZE(cros_ec_dapm_widgets),
> +	.dapm_routes		= cros_ec_dapm_routes,
> +	.num_dapm_routes	= ARRAY_SIZE(cros_ec_dapm_routes),
> +};
> +
> +/*
> + * Platform device and platform driver fro cros-ec-codec.
> + */
> +static int cros_ec_codec_platform_probe(struct platform_device *pd)
> +{
> +	struct device *dev = &pd->dev;
> +	struct cros_ec_device *ec_device = dev_get_drvdata(pd->dev.parent);
> +	struct cros_ec_codec_data *codec_data;
> +	int rc;
> +
> +	codec_data = devm_kzalloc(dev, sizeof(struct cros_ec_codec_data),
> +				  GFP_KERNEL);
> +	if (!codec_data)
> +		return -ENOMEM;
> +
> +	codec_data->dev = dev;
> +	codec_data->ec_device = ec_device;
> +
> +	platform_set_drvdata(pd, codec_data);
> +
> +	rc = snd_soc_register_component(dev, &cros_ec_component_driver,
> +					cros_ec_dai, ARRAY_SIZE(cros_ec_dai));
> +
> +	return 0;

Why ignore errors from snd_soc_register_component() ? Is this on purpose
or an oversight ?

> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id cros_ec_codec_of_match[] = {
> +	{ .compatible = "google,cros-ec-codec" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, cros_ec_codec_of_match);
> +#endif
> +
> +static struct platform_driver cros_ec_codec_platform_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +		.of_match_table = of_match_ptr(cros_ec_codec_of_match),
> +	},
> +	.probe = cros_ec_codec_platform_probe,
> +};
> +
> +module_platform_driver(cros_ec_codec_platform_driver);

The "platform" in the various variable and function names don't really
add any value.

> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("ChromeOS EC codec driver");
> +MODULE_AUTHOR("Cheng-Yi Chiang <cychiang@chromium.org>");
> +MODULE_ALIAS("platform:" DRV_NAME);