ASoC: cs4270: add Master Playback Switch

[firewire-audio.git] / sound / soc / codecs / cs4270.c

/*
 * CS4270 ALSA SoC (ASoC) codec driver
 *
 * Author: Timur Tabi <timur@freescale.com>
 *
 * Copyright 2007-2009 Freescale Semiconductor, Inc.  This file is licensed
 * under the terms of the GNU General Public License version 2.  This
 * program is licensed "as is" without any warranty of any kind, whether
 * express or implied.
 *
 * This is an ASoC device driver for the Cirrus Logic CS4270 codec.
 *
 * Current features/limitations:
 *
 * - Software mode is supported.  Stand-alone mode is not supported.
 * - Only I2C is supported, not SPI
 * - Support for master and slave mode
 * - The machine driver's 'startup' function must call
 *   cs4270_set_dai_sysclk() with the value of MCLK.
 * - Only I2S and left-justified modes are supported
 * - Power management is not supported
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <sound/core.h>
#include <sound/soc.h>
#include <sound/initval.h>
#include <linux/i2c.h>

#include "cs4270.h"

/*
 * The codec isn't really big-endian or little-endian, since the I2S
 * interface requires data to be sent serially with the MSbit first.
 * However, to support BE and LE I2S devices, we specify both here.  That
 * way, ALSA will always match the bit patterns.
 */
#define CS4270_FORMATS (SNDRV_PCM_FMTBIT_S8      | \
                        SNDRV_PCM_FMTBIT_S16_LE  | SNDRV_PCM_FMTBIT_S16_BE  | \
                        SNDRV_PCM_FMTBIT_S18_3LE | SNDRV_PCM_FMTBIT_S18_3BE | \
                        SNDRV_PCM_FMTBIT_S20_3LE | SNDRV_PCM_FMTBIT_S20_3BE | \
                        SNDRV_PCM_FMTBIT_S24_3LE | SNDRV_PCM_FMTBIT_S24_3BE | \
                        SNDRV_PCM_FMTBIT_S24_LE  | SNDRV_PCM_FMTBIT_S24_BE)

/* CS4270 registers addresses */
#define CS4270_CHIPID   0x01    /* Chip ID */
#define CS4270_PWRCTL   0x02    /* Power Control */
#define CS4270_MODE     0x03    /* Mode Control */
#define CS4270_FORMAT   0x04    /* Serial Format, ADC/DAC Control */
#define CS4270_TRANS    0x05    /* Transition Control */
#define CS4270_MUTE     0x06    /* Mute Control */
#define CS4270_VOLA     0x07    /* DAC Channel A Volume Control */
#define CS4270_VOLB     0x08    /* DAC Channel B Volume Control */

#define CS4270_FIRSTREG 0x01
#define CS4270_LASTREG  0x08
#define CS4270_NUMREGS  (CS4270_LASTREG - CS4270_FIRSTREG + 1)

/* Bit masks for the CS4270 registers */
#define CS4270_CHIPID_ID        0xF0
#define CS4270_CHIPID_REV       0x0F
#define CS4270_PWRCTL_FREEZE    0x80
#define CS4270_PWRCTL_PDN_ADC   0x20
#define CS4270_PWRCTL_PDN_DAC   0x02
#define CS4270_PWRCTL_PDN       0x01
#define CS4270_MODE_SPEED_MASK  0x30
#define CS4270_MODE_1X          0x00
#define CS4270_MODE_2X          0x10
#define CS4270_MODE_4X          0x20
#define CS4270_MODE_SLAVE       0x30
#define CS4270_MODE_DIV_MASK    0x0E
#define CS4270_MODE_DIV1        0x00
#define CS4270_MODE_DIV15       0x02
#define CS4270_MODE_DIV2        0x04
#define CS4270_MODE_DIV3        0x06
#define CS4270_MODE_DIV4        0x08
#define CS4270_MODE_POPGUARD    0x01
#define CS4270_FORMAT_FREEZE_A  0x80
#define CS4270_FORMAT_FREEZE_B  0x40
#define CS4270_FORMAT_LOOPBACK  0x20
#define CS4270_FORMAT_DAC_MASK  0x18
#define CS4270_FORMAT_DAC_LJ    0x00
#define CS4270_FORMAT_DAC_I2S   0x08
#define CS4270_FORMAT_DAC_RJ16  0x18
#define CS4270_FORMAT_DAC_RJ24  0x10
#define CS4270_FORMAT_ADC_MASK  0x01
#define CS4270_FORMAT_ADC_LJ    0x00
#define CS4270_FORMAT_ADC_I2S   0x01
#define CS4270_TRANS_ONE_VOL    0x80
#define CS4270_TRANS_SOFT       0x40
#define CS4270_TRANS_ZERO       0x20
#define CS4270_TRANS_INV_ADC_A  0x08
#define CS4270_TRANS_INV_ADC_B  0x10
#define CS4270_TRANS_INV_DAC_A  0x02
#define CS4270_TRANS_INV_DAC_B  0x04
#define CS4270_TRANS_DEEMPH     0x01
#define CS4270_MUTE_AUTO        0x20
#define CS4270_MUTE_ADC_A       0x08
#define CS4270_MUTE_ADC_B       0x10
#define CS4270_MUTE_POLARITY    0x04
#define CS4270_MUTE_DAC_A       0x01
#define CS4270_MUTE_DAC_B       0x02

/* Private data for the CS4270 */
struct cs4270_private {
        struct snd_soc_codec codec;
        u8 reg_cache[CS4270_NUMREGS];
        unsigned int mclk; /* Input frequency of the MCLK pin */
        unsigned int mode; /* The mode (I2S or left-justified) */
        unsigned int slave_mode;
        unsigned int manual_mute;
};

/**
 * struct cs4270_mode_ratios - clock ratio tables
 * @ratio: the ratio of MCLK to the sample rate
 * @speed_mode: the Speed Mode bits to set in the Mode Control register for
 *              this ratio
 * @mclk: the Ratio Select bits to set in the Mode Control register for this
 *        ratio
 *
 * The data for this chart is taken from Table 5 of the CS4270 reference
 * manual.
 *
 * This table is used to determine how to program the Mode Control register.
 * It is also used by cs4270_set_dai_sysclk() to tell ALSA which sampling
 * rates the CS4270 currently supports.
 *
 * @speed_mode is the corresponding bit pattern to be written to the
 * MODE bits of the Mode Control Register
 *
 * @mclk is the corresponding bit pattern to be wirten to the MCLK bits of
 * the Mode Control Register.
 *
 * In situations where a single ratio is represented by multiple speed
 * modes, we favor the slowest speed.  E.g, for a ratio of 128, we pick
 * double-speed instead of quad-speed.  However, the CS4270 errata states
 * that divide-By-1.5 can cause failures, so we avoid that mode where
 * possible.
 *
 * Errata: There is an errata for the CS4270 where divide-by-1.5 does not
 * work if Vd is 3.3V.  If this effects you, select the
 * CONFIG_SND_SOC_CS4270_VD33_ERRATA Kconfig option, and the driver will
 * never select any sample rates that require divide-by-1.5.
 */
struct cs4270_mode_ratios {
        unsigned int ratio;
        u8 speed_mode;
        u8 mclk;
};

static struct cs4270_mode_ratios cs4270_mode_ratios[] = {
        {64, CS4270_MODE_4X, CS4270_MODE_DIV1},
#ifndef CONFIG_SND_SOC_CS4270_VD33_ERRATA
        {96, CS4270_MODE_4X, CS4270_MODE_DIV15},
#endif
        {128, CS4270_MODE_2X, CS4270_MODE_DIV1},
        {192, CS4270_MODE_4X, CS4270_MODE_DIV3},
        {256, CS4270_MODE_1X, CS4270_MODE_DIV1},
        {384, CS4270_MODE_2X, CS4270_MODE_DIV3},
        {512, CS4270_MODE_1X, CS4270_MODE_DIV2},
        {768, CS4270_MODE_1X, CS4270_MODE_DIV3},
        {1024, CS4270_MODE_1X, CS4270_MODE_DIV4}
};

/* The number of MCLK/LRCK ratios supported by the CS4270 */
#define NUM_MCLK_RATIOS         ARRAY_SIZE(cs4270_mode_ratios)

/**
 * cs4270_set_dai_sysclk - determine the CS4270 samples rates.
 * @codec_dai: the codec DAI
 * @clk_id: the clock ID (ignored)
 * @freq: the MCLK input frequency
 * @dir: the clock direction (ignored)
 *
 * This function is used to tell the codec driver what the input MCLK
 * frequency is.
 *
 * The value of MCLK is used to determine which sample rates are supported
 * by the CS4270.  The ratio of MCLK / Fs must be equal to one of nine
 * supported values - 64, 96, 128, 192, 256, 384, 512, 768, and 1024.
 *
 * This function calculates the nine ratios and determines which ones match
 * a standard sample rate.  If there's a match, then it is added to the list
 * of supported sample rates.
 *
 * This function must be called by the machine driver's 'startup' function,
 * otherwise the list of supported sample rates will not be available in
 * time for ALSA.
 */
static int cs4270_set_dai_sysclk(struct snd_soc_dai *codec_dai,
                                 int clk_id, unsigned int freq, int dir)
{
        struct snd_soc_codec *codec = codec_dai->codec;
        struct cs4270_private *cs4270 = codec->private_data;
        unsigned int rates = 0;
        unsigned int rate_min = -1;
        unsigned int rate_max = 0;
        unsigned int i;

        cs4270->mclk = freq;

        for (i = 0; i < NUM_MCLK_RATIOS; i++) {
                unsigned int rate = freq / cs4270_mode_ratios[i].ratio;
                rates |= snd_pcm_rate_to_rate_bit(rate);
                if (rate < rate_min)
                        rate_min = rate;
                if (rate > rate_max)
                        rate_max = rate;
        }
        /* FIXME: soc should support a rate list */
        rates &= ~SNDRV_PCM_RATE_KNOT;

        if (!rates) {
                dev_err(codec->dev, "could not find a valid sample rate\n");
                return -EINVAL;
        }

        codec_dai->playback.rates = rates;
        codec_dai->playback.rate_min = rate_min;
        codec_dai->playback.rate_max = rate_max;

        codec_dai->capture.rates = rates;
        codec_dai->capture.rate_min = rate_min;
        codec_dai->capture.rate_max = rate_max;

        return 0;
}

/**
 * cs4270_set_dai_fmt - configure the codec for the selected audio format
 * @codec_dai: the codec DAI
 * @format: a SND_SOC_DAIFMT_x value indicating the data format
 *
 * This function takes a bitmask of SND_SOC_DAIFMT_x bits and programs the
 * codec accordingly.
 *
 * Currently, this function only supports SND_SOC_DAIFMT_I2S and
 * SND_SOC_DAIFMT_LEFT_J.  The CS4270 codec also supports right-justified
 * data for playback only, but ASoC currently does not support different
 * formats for playback vs. record.
 */
static int cs4270_set_dai_fmt(struct snd_soc_dai *codec_dai,
                              unsigned int format)
{
        struct snd_soc_codec *codec = codec_dai->codec;
        struct cs4270_private *cs4270 = codec->private_data;
        int ret = 0;

        /* set DAI format */
        switch (format & SND_SOC_DAIFMT_FORMAT_MASK) {
        case SND_SOC_DAIFMT_I2S:
        case SND_SOC_DAIFMT_LEFT_J:
                cs4270->mode = format & SND_SOC_DAIFMT_FORMAT_MASK;
                break;
        default:
                dev_err(codec->dev, "invalid dai format\n");
                ret = -EINVAL;
        }

        /* set master/slave audio interface */
        switch (format & SND_SOC_DAIFMT_MASTER_MASK) {
        case SND_SOC_DAIFMT_CBS_CFS:
                cs4270->slave_mode = 1;
                break;
        case SND_SOC_DAIFMT_CBM_CFM:
                cs4270->slave_mode = 0;
                break;
        default:
                /* all other modes are unsupported by the hardware */
                ret = -EINVAL;
        }

        return ret;
}

/**
 * cs4270_fill_cache - pre-fill the CS4270 register cache.
 * @codec: the codec for this CS4270
 *
 * This function fills in the CS4270 register cache by reading the register
 * values from the hardware.
 *
 * This CS4270 registers are cached to avoid excessive I2C I/O operations.
 * After the initial read to pre-fill the cache, the CS4270 never updates
 * the register values, so we won't have a cache coherency problem.
 *
 * We use the auto-increment feature of the CS4270 to read all registers in
 * one shot.
 */
static int cs4270_fill_cache(struct snd_soc_codec *codec)
{
        u8 *cache = codec->reg_cache;
        struct i2c_client *i2c_client = codec->control_data;
        s32 length;

        length = i2c_smbus_read_i2c_block_data(i2c_client,
                CS4270_FIRSTREG | 0x80, CS4270_NUMREGS, cache);

        if (length != CS4270_NUMREGS) {
                dev_err(codec->dev, "i2c read failure, addr=0x%x\n",
                       i2c_client->addr);
                return -EIO;
        }

        return 0;
}

/**
 * cs4270_read_reg_cache - read from the CS4270 register cache.
 * @codec: the codec for this CS4270
 * @reg: the register to read
 *
 * This function returns the value for a given register.  It reads only from
 * the register cache, not the hardware itself.
 *
 * This CS4270 registers are cached to avoid excessive I2C I/O operations.
 * After the initial read to pre-fill the cache, the CS4270 never updates
 * the register values, so we won't have a cache coherency problem.
 */
static unsigned int cs4270_read_reg_cache(struct snd_soc_codec *codec,
        unsigned int reg)
{
        u8 *cache = codec->reg_cache;

        if ((reg < CS4270_FIRSTREG) || (reg > CS4270_LASTREG))
                return -EIO;

        return cache[reg - CS4270_FIRSTREG];
}

/**
 * cs4270_i2c_write - write to a CS4270 register via the I2C bus.
 * @codec: the codec for this CS4270
 * @reg: the register to write
 * @value: the value to write to the register
 *
 * This function writes the given value to the given CS4270 register, and
 * also updates the register cache.
 *
 * Note that we don't use the hw_write function pointer of snd_soc_codec.
 * That's because it's too clunky: the hw_write_t prototype does not match
 * i2c_smbus_write_byte_data(), and it's just another layer of overhead.
 */
static int cs4270_i2c_write(struct snd_soc_codec *codec, unsigned int reg,
                            unsigned int value)
{
        u8 *cache = codec->reg_cache;

        if ((reg < CS4270_FIRSTREG) || (reg > CS4270_LASTREG))
                return -EIO;

        /* Only perform an I2C operation if the new value is different */
        if (cache[reg - CS4270_FIRSTREG] != value) {
                struct i2c_client *client = codec->control_data;
                if (i2c_smbus_write_byte_data(client, reg, value)) {
                        dev_err(codec->dev, "i2c write failed\n");
                        return -EIO;
                }

                /* We've written to the hardware, so update the cache */
                cache[reg - CS4270_FIRSTREG] = value;
        }

        return 0;
}

/**
 * cs4270_hw_params - program the CS4270 with the given hardware parameters.
 * @substream: the audio stream
 * @params: the hardware parameters to set
 * @dai: the SOC DAI (ignored)
 *
 * This function programs the hardware with the values provided.
 * Specifically, the sample rate and the data format.
 *
 * The .ops functions are used to provide board-specific data, like input
 * frequencies, to this driver.  This function takes that information,
 * combines it with the hardware parameters provided, and programs the
 * hardware accordingly.
 */
static int cs4270_hw_params(struct snd_pcm_substream *substream,
                            struct snd_pcm_hw_params *params,
                            struct snd_soc_dai *dai)
{
        struct snd_soc_pcm_runtime *rtd = substream->private_data;
        struct snd_soc_device *socdev = rtd->socdev;
        struct snd_soc_codec *codec = socdev->card->codec;
        struct cs4270_private *cs4270 = codec->private_data;
        int ret;
        unsigned int i;
        unsigned int rate;
        unsigned int ratio;
        int reg;

        /* Figure out which MCLK/LRCK ratio to use */

        rate = params_rate(params);     /* Sampling rate, in Hz */
        ratio = cs4270->mclk / rate;    /* MCLK/LRCK ratio */

        for (i = 0; i < NUM_MCLK_RATIOS; i++) {
                if (cs4270_mode_ratios[i].ratio == ratio)
                        break;
        }

        if (i == NUM_MCLK_RATIOS) {
                /* We did not find a matching ratio */
                dev_err(codec->dev, "could not find matching ratio\n");
                return -EINVAL;
        }

        /* Set the sample rate */

        reg = snd_soc_read(codec, CS4270_MODE);
        reg &= ~(CS4270_MODE_SPEED_MASK | CS4270_MODE_DIV_MASK);
        reg |= cs4270_mode_ratios[i].mclk;

        if (cs4270->slave_mode)
                reg |= CS4270_MODE_SLAVE;
        else
                reg |= cs4270_mode_ratios[i].speed_mode;

        ret = snd_soc_write(codec, CS4270_MODE, reg);
        if (ret < 0) {
                dev_err(codec->dev, "i2c write failed\n");
                return ret;
        }

        /* Set the DAI format */

        reg = snd_soc_read(codec, CS4270_FORMAT);
        reg &= ~(CS4270_FORMAT_DAC_MASK | CS4270_FORMAT_ADC_MASK);

        switch (cs4270->mode) {
        case SND_SOC_DAIFMT_I2S:
                reg |= CS4270_FORMAT_DAC_I2S | CS4270_FORMAT_ADC_I2S;
                break;
        case SND_SOC_DAIFMT_LEFT_J:
                reg |= CS4270_FORMAT_DAC_LJ | CS4270_FORMAT_ADC_LJ;
                break;
        default:
                dev_err(codec->dev, "unknown dai format\n");
                return -EINVAL;
        }

        ret = snd_soc_write(codec, CS4270_FORMAT, reg);
        if (ret < 0) {
                dev_err(codec->dev, "i2c write failed\n");
                return ret;
        }

        return ret;
}

/**
 * cs4270_dai_mute - enable/disable the CS4270 external mute
 * @dai: the SOC DAI
 * @mute: 0 = disable mute, 1 = enable mute
 *
 * This function toggles the mute bits in the MUTE register.  The CS4270's
 * mute capability is intended for external muting circuitry, so if the
 * board does not have the MUTEA or MUTEB pins connected to such circuitry,
 * then this function will do nothing.
 */
static int cs4270_dai_mute(struct snd_soc_dai *dai, int mute)
{
        struct snd_soc_codec *codec = dai->codec;
        struct cs4270_private *cs4270 = codec->private_data;
        int reg6;

        reg6 = snd_soc_read(codec, CS4270_MUTE);

        if (mute)
                reg6 |= CS4270_MUTE_DAC_A | CS4270_MUTE_DAC_B;
        else {
                reg6 &= ~(CS4270_MUTE_DAC_A | CS4270_MUTE_DAC_B);
                reg6 |= cs4270->manual_mute;
        }

        return snd_soc_write(codec, CS4270_MUTE, reg6);
}

/**
 * cs4270_soc_put_mute - put callback for the 'Master Playback switch'
 *                       alsa control.
 * @kcontrol: mixer control
 * @ucontrol: control element information
 *
 * This function basically passes the arguments on to the generic
 * snd_soc_put_volsw() function and saves the mute information in
 * our private data structure. This is because we want to prevent
 * cs4270_dai_mute() neglecting the user's decision to manually
 * mute the codec's output.
 *
 * Returns 0 for success.
 */
static int cs4270_soc_put_mute(struct snd_kcontrol *kcontrol,
                                struct snd_ctl_elem_value *ucontrol)
{
        struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
        struct cs4270_private *cs4270 = codec->private_data;
        int left = !ucontrol->value.integer.value[0];
        int right = !ucontrol->value.integer.value[1];

        cs4270->manual_mute = (left ? CS4270_MUTE_DAC_A : 0) |
                              (right ? CS4270_MUTE_DAC_B : 0);

        return snd_soc_put_volsw(kcontrol, ucontrol);
}

/* A list of non-DAPM controls that the CS4270 supports */
static const struct snd_kcontrol_new cs4270_snd_controls[] = {
        SOC_DOUBLE_R("Master Playback Volume",
                CS4270_VOLA, CS4270_VOLB, 0, 0xFF, 1),
        SOC_SINGLE("Digital Sidetone Switch", CS4270_FORMAT, 5, 1, 0),
        SOC_SINGLE("Soft Ramp Switch", CS4270_TRANS, 6, 1, 0),
        SOC_SINGLE("Zero Cross Switch", CS4270_TRANS, 5, 1, 0),
        SOC_SINGLE("Popguard Switch", CS4270_MODE, 0, 1, 1),
        SOC_SINGLE("Auto-Mute Switch", CS4270_MUTE, 5, 1, 0),
        SOC_DOUBLE("Master Capture Switch", CS4270_MUTE, 3, 4, 1, 1),
        SOC_DOUBLE_EXT("Master Playback Switch", CS4270_MUTE, 0, 1, 1, 1,
                snd_soc_get_volsw, cs4270_soc_put_mute),
};

/*
 * cs4270_codec - global variable to store codec for the ASoC probe function
 *
 * If struct i2c_driver had a private_data field, we wouldn't need to use
 * cs4270_codec.  This is the only way to pass the codec structure from
 * cs4270_i2c_probe() to cs4270_probe().  Unfortunately, there is no good
 * way to synchronize these two functions.  cs4270_i2c_probe() can be called
 * multiple times before cs4270_probe() is called even once.  So for now, we
 * also only allow cs4270_i2c_probe() to be run once.  That means that we do
 * not support more than one cs4270 device in the system, at least for now.
 */
static struct snd_soc_codec *cs4270_codec;

static struct snd_soc_dai_ops cs4270_dai_ops = {
        .hw_params      = cs4270_hw_params,
        .set_sysclk     = cs4270_set_dai_sysclk,
        .set_fmt        = cs4270_set_dai_fmt,
        .digital_mute   = cs4270_dai_mute,
};

struct snd_soc_dai cs4270_dai = {
        .name = "cs4270",
        .playback = {
                .stream_name = "Playback",
                .channels_min = 1,
                .channels_max = 2,
                .rates = 0,
                .formats = CS4270_FORMATS,
        },
        .capture = {
                .stream_name = "Capture",
                .channels_min = 1,
                .channels_max = 2,
                .rates = 0,
                .formats = CS4270_FORMATS,
        },
        .ops = &cs4270_dai_ops,
};
EXPORT_SYMBOL_GPL(cs4270_dai);

/**
 * cs4270_probe - ASoC probe function
 * @pdev: platform device
 *
 * This function is called when ASoC has all the pieces it needs to
 * instantiate a sound driver.
 */
static int cs4270_probe(struct platform_device *pdev)
{
        struct snd_soc_device *socdev = platform_get_drvdata(pdev);
        struct snd_soc_codec *codec = cs4270_codec;
        int ret;

        /* Connect the codec to the socdev.  snd_soc_new_pcms() needs this. */
        socdev->card->codec = codec;

        /* Register PCMs */
        ret = snd_soc_new_pcms(socdev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1);
        if (ret < 0) {
                dev_err(codec->dev, "failed to create pcms\n");
                return ret;
        }

        /* Add the non-DAPM controls */
        ret = snd_soc_add_controls(codec, cs4270_snd_controls,
                                ARRAY_SIZE(cs4270_snd_controls));
        if (ret < 0) {
                dev_err(codec->dev, "failed to add controls\n");
                goto error_free_pcms;
        }

        /* And finally, register the socdev */
        ret = snd_soc_init_card(socdev);
        if (ret < 0) {
                dev_err(codec->dev, "failed to register card\n");
                goto error_free_pcms;
        }

        return 0;

error_free_pcms:
        snd_soc_free_pcms(socdev);

        return ret;
}

/**
 * cs4270_remove - ASoC remove function
 * @pdev: platform device
 *
 * This function is the counterpart to cs4270_probe().
 */
static int cs4270_remove(struct platform_device *pdev)
{
        struct snd_soc_device *socdev = platform_get_drvdata(pdev);

        snd_soc_free_pcms(socdev);

        return 0;
};

/**
 * cs4270_i2c_probe - initialize the I2C interface of the CS4270
 * @i2c_client: the I2C client object
 * @id: the I2C device ID (ignored)
 *
 * This function is called whenever the I2C subsystem finds a device that
 * matches the device ID given via a prior call to i2c_add_driver().
 */
static int cs4270_i2c_probe(struct i2c_client *i2c_client,
        const struct i2c_device_id *id)
{
        struct snd_soc_codec *codec;
        struct cs4270_private *cs4270;
        unsigned int reg;
        int ret;

        /* For now, we only support one cs4270 device in the system.  See the
         * comment for cs4270_codec.
         */
        if (cs4270_codec) {
                dev_err(&i2c_client->dev, "ignoring CS4270 at addr %X\n",
                       i2c_client->addr);
                dev_err(&i2c_client->dev, "only one per board allowed\n");
                /* Should we return something other than ENODEV here? */
                return -ENODEV;
        }

        /* Verify that we have a CS4270 */

        ret = i2c_smbus_read_byte_data(i2c_client, CS4270_CHIPID);
        if (ret < 0) {
                dev_err(&i2c_client->dev, "failed to read i2c at addr %X\n",
                       i2c_client->addr);
                return ret;
        }
        /* The top four bits of the chip ID should be 1100. */
        if ((ret & 0xF0) != 0xC0) {
                dev_err(&i2c_client->dev, "device at addr %X is not a CS4270\n",
                       i2c_client->addr);
                return -ENODEV;
        }

        dev_info(&i2c_client->dev, "found device at i2c address %X\n",
                i2c_client->addr);
        dev_info(&i2c_client->dev, "hardware revision %X\n", ret & 0xF);

        /* Allocate enough space for the snd_soc_codec structure
           and our private data together. */
        cs4270 = kzalloc(sizeof(struct cs4270_private), GFP_KERNEL);
        if (!cs4270) {
                dev_err(&i2c_client->dev, "could not allocate codec\n");
                return -ENOMEM;
        }
        codec = &cs4270->codec;

        mutex_init(&codec->mutex);
        INIT_LIST_HEAD(&codec->dapm_widgets);
        INIT_LIST_HEAD(&codec->dapm_paths);

        codec->dev = &i2c_client->dev;
        codec->name = "CS4270";
        codec->owner = THIS_MODULE;
        codec->dai = &cs4270_dai;
        codec->num_dai = 1;
        codec->private_data = cs4270;
        codec->control_data = i2c_client;
        codec->read = cs4270_read_reg_cache;
        codec->write = cs4270_i2c_write;
        codec->reg_cache = cs4270->reg_cache;
        codec->reg_cache_size = CS4270_NUMREGS;

        /* The I2C interface is set up, so pre-fill our register cache */

        ret = cs4270_fill_cache(codec);
        if (ret < 0) {
                dev_err(&i2c_client->dev, "failed to fill register cache\n");
                goto error_free_codec;
        }

        /* Disable auto-mute.  This feature appears to be buggy.  In some
         * situations, auto-mute will not deactivate when it should, so we want
         * this feature disabled by default.  An application (e.g. alsactl) can
         * re-enabled it by using the controls.
         */

        reg = cs4270_read_reg_cache(codec, CS4270_MUTE);
        reg &= ~CS4270_MUTE_AUTO;
        ret = cs4270_i2c_write(codec, CS4270_MUTE, reg);
        if (ret < 0) {
                dev_err(&i2c_client->dev, "i2c write failed\n");
                return ret;
        }

        /* Disable automatic volume control.  The hardware enables, and it
         * causes volume change commands to be delayed, sometimes until after
         * playback has started.  An application (e.g. alsactl) can
         * re-enabled it by using the controls.
         */

        reg = cs4270_read_reg_cache(codec, CS4270_TRANS);
        reg &= ~(CS4270_TRANS_SOFT | CS4270_TRANS_ZERO);
        ret = cs4270_i2c_write(codec, CS4270_TRANS, reg);
        if (ret < 0) {
                dev_err(&i2c_client->dev, "i2c write failed\n");
                return ret;
        }

        /* Initialize the DAI. Normally, we'd prefer to have a kmalloc'd DAI
         * structure for each CS4270 device, but the machine driver needs to
         * have a pointer to the DAI structure, so for now it must be a global
         * variable.
         */
        cs4270_dai.dev = &i2c_client->dev;

        /* Register the DAI.  If all the other ASoC driver have already
         * registered, then this will call our probe function, so
         * cs4270_codec needs to be ready.
         */
        cs4270_codec = codec;
        ret = snd_soc_register_dai(&cs4270_dai);
        if (ret < 0) {
                dev_err(&i2c_client->dev, "failed to register DAIe\n");
                goto error_free_codec;
        }

        i2c_set_clientdata(i2c_client, cs4270);

        return 0;

error_free_codec:
        kfree(cs4270);
        cs4270_codec = NULL;
        cs4270_dai.dev = NULL;

        return ret;
}

/**
 * cs4270_i2c_remove - remove an I2C device
 * @i2c_client: the I2C client object
 *
 * This function is the counterpart to cs4270_i2c_probe().
 */
static int cs4270_i2c_remove(struct i2c_client *i2c_client)
{
        struct cs4270_private *cs4270 = i2c_get_clientdata(i2c_client);

        kfree(cs4270);
        cs4270_codec = NULL;
        cs4270_dai.dev = NULL;

        return 0;
}

/*
 * cs4270_id - I2C device IDs supported by this driver
 */
static struct i2c_device_id cs4270_id[] = {
        {"cs4270", 0},
        {}
};
MODULE_DEVICE_TABLE(i2c, cs4270_id);

/*
 * cs4270_i2c_driver - I2C device identification
 *
 * This structure tells the I2C subsystem how to identify and support a
 * given I2C device type.
 */
static struct i2c_driver cs4270_i2c_driver = {
        .driver = {
                .name = "cs4270",
                .owner = THIS_MODULE,
        },
        .id_table = cs4270_id,
        .probe = cs4270_i2c_probe,
        .remove = cs4270_i2c_remove,
};

/*
 * ASoC codec device structure
 *
 * Assign this variable to the codec_dev field of the machine driver's
 * snd_soc_device structure.
 */
struct snd_soc_codec_device soc_codec_device_cs4270 = {
        .probe =        cs4270_probe,
        .remove =       cs4270_remove
};
EXPORT_SYMBOL_GPL(soc_codec_device_cs4270);

static int __init cs4270_init(void)
{
        pr_info("Cirrus Logic CS4270 ALSA SoC Codec Driver\n");

        return i2c_add_driver(&cs4270_i2c_driver);
}
module_init(cs4270_init);

static void __exit cs4270_exit(void)
{
        i2c_del_driver(&cs4270_i2c_driver);
}
module_exit(cs4270_exit);

MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
MODULE_DESCRIPTION("Cirrus Logic CS4270 ALSA SoC Codec Driver");
MODULE_LICENSE("GPL");