/*
 * ALSA SoC I2S Audio Layer for Broadcom BCM2835 SoC
 *
 * Author:      Florian Meier <florian.meier@koalo.de>
 *              Copyright 2013
 *
 * Based on
 *      Raspberry Pi PCM I2S ALSA Driver
 *      Copyright (c) by Phil Poole 2013
 *
 *      ALSA SoC I2S (McBSP) Audio Layer for TI DAVINCI processor
 *      Vladimir Barinov, <vbarinov@embeddedalley.com>
 *      Copyright (C) 2007 MontaVista Software, Inc., <source@mvista.com>
 *
 *      OMAP ALSA SoC DAI driver using McBSP port
 *      Copyright (C) 2008 Nokia Corporation
 *      Contact: Jarkko Nikula <jarkko.nikula@bitmer.com>
 *               Peter Ujfalusi <peter.ujfalusi@ti.com>
 *
 *      Freescale SSI ALSA SoC Digital Audio Interface (DAI) driver
 *      Author: Timur Tabi <timur@freescale.com>
 *      Copyright 2007-2010 Freescale Semiconductor, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/slab.h>

#include <sound/core.h>
#include <sound/dmaengine_pcm.h>
#include <sound/initval.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <sound/soc.h>

/* I2S registers */
#define BCM2835_I2S_CS_A_REG            0x00
#define BCM2835_I2S_FIFO_A_REG          0x04
#define BCM2835_I2S_MODE_A_REG          0x08
#define BCM2835_I2S_RXC_A_REG           0x0c
#define BCM2835_I2S_TXC_A_REG           0x10
#define BCM2835_I2S_DREQ_A_REG          0x14
#define BCM2835_I2S_INTEN_A_REG 0x18
#define BCM2835_I2S_INTSTC_A_REG        0x1c
#define BCM2835_I2S_GRAY_REG            0x20

/* I2S register settings */
#define BCM2835_I2S_STBY                BIT(25)
#define BCM2835_I2S_SYNC                BIT(24)
#define BCM2835_I2S_RXSEX               BIT(23)
#define BCM2835_I2S_RXF         BIT(22)
#define BCM2835_I2S_TXE         BIT(21)
#define BCM2835_I2S_RXD         BIT(20)
#define BCM2835_I2S_TXD         BIT(19)
#define BCM2835_I2S_RXR         BIT(18)
#define BCM2835_I2S_TXW         BIT(17)
#define BCM2835_I2S_CS_RXERR            BIT(16)
#define BCM2835_I2S_CS_TXERR            BIT(15)
#define BCM2835_I2S_RXSYNC              BIT(14)
#define BCM2835_I2S_TXSYNC              BIT(13)
#define BCM2835_I2S_DMAEN               BIT(9)
#define BCM2835_I2S_RXTHR(v)            ((v) << 7)
#define BCM2835_I2S_TXTHR(v)            ((v) << 5)
#define BCM2835_I2S_RXCLR               BIT(4)
#define BCM2835_I2S_TXCLR               BIT(3)
#define BCM2835_I2S_TXON                BIT(2)
#define BCM2835_I2S_RXON                BIT(1)
#define BCM2835_I2S_EN                  (1)

#define BCM2835_I2S_CLKDIS              BIT(28)
#define BCM2835_I2S_PDMN                BIT(27)
#define BCM2835_I2S_PDME                BIT(26)
#define BCM2835_I2S_FRXP                BIT(25)
#define BCM2835_I2S_FTXP                BIT(24)
#define BCM2835_I2S_CLKM                BIT(23)
#define BCM2835_I2S_CLKI                BIT(22)
#define BCM2835_I2S_FSM         BIT(21)
#define BCM2835_I2S_FSI         BIT(20)
#define BCM2835_I2S_FLEN(v)             ((v) << 10)
#define BCM2835_I2S_FSLEN(v)            (v)

#define BCM2835_I2S_CHWEX               BIT(15)
#define BCM2835_I2S_CHEN                BIT(14)
#define BCM2835_I2S_CHPOS(v)            ((v) << 4)
#define BCM2835_I2S_CHWID(v)            (v)
#define BCM2835_I2S_CH1(v)              ((v) << 16)
#define BCM2835_I2S_CH2(v)              (v)
#define BCM2835_I2S_CH1_POS(v)          BCM2835_I2S_CH1(BCM2835_I2S_CHPOS(v))
#define BCM2835_I2S_CH2_POS(v)          BCM2835_I2S_CH2(BCM2835_I2S_CHPOS(v))

#define BCM2835_I2S_TX_PANIC(v) ((v) << 24)
#define BCM2835_I2S_RX_PANIC(v) ((v) << 16)
#define BCM2835_I2S_TX(v)               ((v) << 8)
#define BCM2835_I2S_RX(v)               (v)

#define BCM2835_I2S_INT_RXERR           BIT(3)
#define BCM2835_I2S_INT_TXERR           BIT(2)
#define BCM2835_I2S_INT_RXR             BIT(1)
#define BCM2835_I2S_INT_TXW             BIT(0)

/* Frame length register is 10 bit, maximum length 1024 */
#define BCM2835_I2S_MAX_FRAME_LENGTH    1024

/* General device struct */
struct bcm2835_i2s_dev {
        struct device                           *dev;
        struct snd_dmaengine_dai_dma_data       dma_data[2];
        unsigned int                            fmt;
        unsigned int                            tdm_slots;
        unsigned int                            rx_mask;
        unsigned int                            tx_mask;
        unsigned int                            slot_width;
        unsigned int                            frame_length;

        struct regmap                           *i2s_regmap;
        struct clk                              *clk;
        bool                                    clk_prepared;
        int                                     clk_rate;
};

static void bcm2835_i2s_start_clock(struct bcm2835_i2s_dev *dev)
{
        unsigned int master = dev->fmt & SND_SOC_DAIFMT_MASTER_MASK;

        if (dev->clk_prepared)
                return;

        switch (master) {
        case SND_SOC_DAIFMT_CBS_CFS:
        case SND_SOC_DAIFMT_CBS_CFM:
                clk_prepare_enable(dev->clk);
                dev->clk_prepared = true;
                break;
        default:
                break;
        }
}

static void bcm2835_i2s_stop_clock(struct bcm2835_i2s_dev *dev)
{
        if (dev->clk_prepared)
                clk_disable_unprepare(dev->clk);
        dev->clk_prepared = false;
}

static void bcm2835_i2s_clear_fifos(struct bcm2835_i2s_dev *dev,
                                    bool tx, bool rx)
{
        int timeout = 1000;
        uint32_t syncval;
        uint32_t csreg;
        uint32_t i2s_active_state;
        bool clk_was_prepared;
        uint32_t off;
        uint32_t clr;

        off =  tx ? BCM2835_I2S_TXON : 0;
        off |= rx ? BCM2835_I2S_RXON : 0;

        clr =  tx ? BCM2835_I2S_TXCLR : 0;
        clr |= rx ? BCM2835_I2S_RXCLR : 0;

        /* Backup the current state */
        regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
        i2s_active_state = csreg & (BCM2835_I2S_RXON | BCM2835_I2S_TXON);

        /* Start clock if not running */
        clk_was_prepared = dev->clk_prepared;
        if (!clk_was_prepared)
                bcm2835_i2s_start_clock(dev);

        /* Stop I2S module */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, off, 0);

        /*
         * Clear the FIFOs
         * Requires at least 2 PCM clock cycles to take effect
         */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, clr, clr);

        /* Wait for 2 PCM clock cycles */

        /*
         * Toggle the SYNC flag. After 2 PCM clock cycles it can be read back
         * FIXME: This does not seem to work for slave mode!
         */
        regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &syncval);
        syncval &= BCM2835_I2S_SYNC;

        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_SYNC, ~syncval);

        /* Wait for the SYNC flag changing it's state */
        while (--timeout) {
                regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
                if ((csreg & BCM2835_I2S_SYNC) != syncval)
                        break;
        }

        if (!timeout)
                dev_err(dev->dev, "I2S SYNC error!\n");

        /* Stop clock if it was not running before */
        if (!clk_was_prepared)
                bcm2835_i2s_stop_clock(dev);

        /* Restore I2S state */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_RXON | BCM2835_I2S_TXON, i2s_active_state);
}

static int bcm2835_i2s_set_dai_fmt(struct snd_soc_dai *dai,
                                      unsigned int fmt)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
        dev->fmt = fmt;
        return 0;
}

static int bcm2835_i2s_set_dai_bclk_ratio(struct snd_soc_dai *dai,
                                      unsigned int ratio)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);

        if (!ratio) {
                dev->tdm_slots = 0;
                return 0;
        }

        if (ratio > BCM2835_I2S_MAX_FRAME_LENGTH)
                return -EINVAL;

        dev->tdm_slots = 2;
        dev->rx_mask = 0x03;
        dev->tx_mask = 0x03;
        dev->slot_width = ratio / 2;
        dev->frame_length = ratio;

        return 0;
}

static int bcm2835_i2s_set_dai_tdm_slot(struct snd_soc_dai *dai,
        unsigned int tx_mask, unsigned int rx_mask,
        int slots, int width)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);

        if (slots) {
                if (slots < 0 || width < 0)
                        return -EINVAL;

                /* Limit masks to available slots */
                rx_mask &= GENMASK(slots - 1, 0);
                tx_mask &= GENMASK(slots - 1, 0);

                /*
                 * The driver is limited to 2-channel setups.
                 * Check that exactly 2 bits are set in the masks.
                 */
                if (hweight_long((unsigned long) rx_mask) != 2
                    || hweight_long((unsigned long) tx_mask) != 2)
                        return -EINVAL;

                if (slots * width > BCM2835_I2S_MAX_FRAME_LENGTH)
                        return -EINVAL;
        }

        dev->tdm_slots = slots;

        dev->rx_mask = rx_mask;
        dev->tx_mask = tx_mask;
        dev->slot_width = width;
        dev->frame_length = slots * width;

        return 0;
}

/*
 * Convert logical slot number into physical slot number.
 *
 * If odd_offset is 0 sequential number is identical to logical number.
 * This is used for DSP modes with slot numbering 0 1 2 3 ...
 *
 * Otherwise odd_offset defines the physical offset for odd numbered
 * slots. This is used for I2S and left/right justified modes to
 * translate from logical slot numbers 0 1 2 3 ... into physical slot
 * numbers 0 2 ... 3 4 ...
 */
static int bcm2835_i2s_convert_slot(unsigned int slot, unsigned int odd_offset)
{
        if (!odd_offset)
                return slot;

        if (slot & 1)
                return (slot >> 1) + odd_offset;

        return slot >> 1;
}

/*
 * Calculate channel position from mask and slot width.
 *
 * Mask must contain exactly 2 set bits.
 * Lowest set bit is channel 1 position, highest set bit channel 2.
 * The constant offset is added to both channel positions.
 *
 * If odd_offset is > 0 slot positions are translated to
 * I2S-style TDM slot numbering ( 0 2 ... 3 4 ...) with odd
 * logical slot numbers starting at physical slot odd_offset.
 */
static void bcm2835_i2s_calc_channel_pos(
        unsigned int *ch1_pos, unsigned int *ch2_pos,
        unsigned int mask, unsigned int width,
        unsigned int bit_offset, unsigned int odd_offset)
{
        *ch1_pos = bcm2835_i2s_convert_slot((ffs(mask) - 1), odd_offset)
                        * width + bit_offset;
        *ch2_pos = bcm2835_i2s_convert_slot((fls(mask) - 1), odd_offset)
                        * width + bit_offset;
}

static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
                                 struct snd_pcm_hw_params *params,
                                 struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
        unsigned int data_length, data_delay, framesync_length;
        unsigned int slots, slot_width, odd_slot_offset;
        int frame_length, bclk_rate;
        unsigned int rx_mask, tx_mask;
        unsigned int rx_ch1_pos, rx_ch2_pos, tx_ch1_pos, tx_ch2_pos;
        unsigned int mode, format;
        bool bit_clock_master = false;
        bool frame_sync_master = false;
        bool frame_start_falling_edge = false;
        uint32_t csreg;
        int ret = 0;

        /*
         * If a stream is already enabled,
         * the registers are already set properly.
         */
        regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);

        if (csreg & (BCM2835_I2S_TXON | BCM2835_I2S_RXON))
                return 0;

        data_length = params_width(params);
        data_delay = 0;
        odd_slot_offset = 0;
        mode = 0;

        if (dev->tdm_slots) {
                slots = dev->tdm_slots;
                slot_width = dev->slot_width;
                frame_length = dev->frame_length;
                rx_mask = dev->rx_mask;
                tx_mask = dev->tx_mask;
                bclk_rate = dev->frame_length * params_rate(params);
        } else {
                slots = 2;
                slot_width = params_width(params);
                rx_mask = 0x03;
                tx_mask = 0x03;

                frame_length = snd_soc_params_to_frame_size(params);
                if (frame_length < 0)
                        return frame_length;

                bclk_rate = snd_soc_params_to_bclk(params);
                if (bclk_rate < 0)
                        return bclk_rate;
        }

        /* Check if data fits into slots */
        if (data_length > slot_width)
                return -EINVAL;

        /* Check if CPU is bit clock master */
        switch (dev->fmt & SND_SOC_DAIFMT_MASTER_MASK) {
        case SND_SOC_DAIFMT_CBS_CFS:
        case SND_SOC_DAIFMT_CBS_CFM:
                bit_clock_master = true;
                break;
        case SND_SOC_DAIFMT_CBM_CFS:
        case SND_SOC_DAIFMT_CBM_CFM:
                bit_clock_master = false;
                break;
        default:
                return -EINVAL;
        }

        /* Check if CPU is frame sync master */
        switch (dev->fmt & SND_SOC_DAIFMT_MASTER_MASK) {
        case SND_SOC_DAIFMT_CBS_CFS:
        case SND_SOC_DAIFMT_CBM_CFS:
                frame_sync_master = true;
                break;
        case SND_SOC_DAIFMT_CBS_CFM:
        case SND_SOC_DAIFMT_CBM_CFM:
                frame_sync_master = false;
                break;
        default:
                return -EINVAL;
        }

        /* Clock should only be set up here if CPU is clock master */
        if (bit_clock_master &&
            (!dev->clk_prepared || dev->clk_rate != bclk_rate)) {
                if (dev->clk_prepared)
                        bcm2835_i2s_stop_clock(dev);

                if (dev->clk_rate != bclk_rate) {
                        ret = clk_set_rate(dev->clk, bclk_rate);
                        if (ret)
                                return ret;
                        dev->clk_rate = bclk_rate;
                }

                bcm2835_i2s_start_clock(dev);
        }

        /* Setup the frame format */
        format = BCM2835_I2S_CHEN;

        if (data_length >= 24)
                format |= BCM2835_I2S_CHWEX;

        format |= BCM2835_I2S_CHWID((data_length-8)&0xf);

        /* CH2 format is the same as for CH1 */
        format = BCM2835_I2S_CH1(format) | BCM2835_I2S_CH2(format);

        switch (dev->fmt & SND_SOC_DAIFMT_FORMAT_MASK) {
        case SND_SOC_DAIFMT_I2S:
                /* I2S mode needs an even number of slots */
                if (slots & 1)
                        return -EINVAL;

                /*
                 * Use I2S-style logical slot numbering: even slots
                 * are in first half of frame, odd slots in second half.
                 */
                odd_slot_offset = slots >> 1;

                /* MSB starts one cycle after frame start */
                data_delay = 1;

                /* Setup frame sync signal for 50% duty cycle */
                framesync_length = frame_length / 2;
                frame_start_falling_edge = true;
                break;
        case SND_SOC_DAIFMT_LEFT_J:
                if (slots & 1)
                        return -EINVAL;

                odd_slot_offset = slots >> 1;
                data_delay = 0;
                framesync_length = frame_length / 2;
                frame_start_falling_edge = false;
                break;
        case SND_SOC_DAIFMT_RIGHT_J:
                if (slots & 1)
                        return -EINVAL;

                /* Odd frame lengths aren't supported */
                if (frame_length & 1)
                        return -EINVAL;

                odd_slot_offset = slots >> 1;
                data_delay = slot_width - data_length;
                framesync_length = frame_length / 2;
                frame_start_falling_edge = false;
                break;
        case SND_SOC_DAIFMT_DSP_A:
                data_delay = 1;
                framesync_length = 1;
                frame_start_falling_edge = false;
                break;
        case SND_SOC_DAIFMT_DSP_B:
                data_delay = 0;
                framesync_length = 1;
                frame_start_falling_edge = false;
                break;
        default:
                return -EINVAL;
        }

        bcm2835_i2s_calc_channel_pos(&rx_ch1_pos, &rx_ch2_pos,
                rx_mask, slot_width, data_delay, odd_slot_offset);
        bcm2835_i2s_calc_channel_pos(&tx_ch1_pos, &tx_ch2_pos,
                tx_mask, slot_width, data_delay, odd_slot_offset);

        /*
         * Transmitting data immediately after frame start, eg
         * in left-justified or DSP mode A, only works stable
         * if bcm2835 is the frame clock master.
         */
        if ((!rx_ch1_pos || !tx_ch1_pos) && !frame_sync_master)
                dev_warn(dev->dev,
                        "Unstable slave config detected, L/R may be swapped");

        /*
         * Set format for both streams.
         * We cannot set another frame length
         * (and therefore word length) anyway,
         * so the format will be the same.
         */
        regmap_write(dev->i2s_regmap, BCM2835_I2S_RXC_A_REG, 
                  format
                | BCM2835_I2S_CH1_POS(rx_ch1_pos)
                | BCM2835_I2S_CH2_POS(rx_ch2_pos));
        regmap_write(dev->i2s_regmap, BCM2835_I2S_TXC_A_REG, 
                  format
                | BCM2835_I2S_CH1_POS(tx_ch1_pos)
                | BCM2835_I2S_CH2_POS(tx_ch2_pos));

        /* Setup the I2S mode */

        if (data_length <= 16) {
                /*
                 * Use frame packed mode (2 channels per 32 bit word)
                 * We cannot set another frame length in the second stream
                 * (and therefore word length) anyway,
                 * so the format will be the same.
                 */
                mode |= BCM2835_I2S_FTXP | BCM2835_I2S_FRXP;
        }

        mode |= BCM2835_I2S_FLEN(frame_length - 1);
        mode |= BCM2835_I2S_FSLEN(framesync_length);

        /* CLKM selects bcm2835 clock slave mode */
        if (!bit_clock_master)
                mode |= BCM2835_I2S_CLKM;

        /* FSM selects bcm2835 frame sync slave mode */
        if (!frame_sync_master)
                mode |= BCM2835_I2S_FSM;

        /* CLKI selects normal clocking mode, sampling on rising edge */
        switch (dev->fmt & SND_SOC_DAIFMT_INV_MASK) {
        case SND_SOC_DAIFMT_NB_NF:
        case SND_SOC_DAIFMT_NB_IF:
                mode |= BCM2835_I2S_CLKI;
                break;
        case SND_SOC_DAIFMT_IB_NF:
        case SND_SOC_DAIFMT_IB_IF:
                break;
        default:
                return -EINVAL;
        }

        /* FSI selects frame start on falling edge */
        switch (dev->fmt & SND_SOC_DAIFMT_INV_MASK) {
        case SND_SOC_DAIFMT_NB_NF:
        case SND_SOC_DAIFMT_IB_NF:
                if (frame_start_falling_edge)
                        mode |= BCM2835_I2S_FSI;
                break;
        case SND_SOC_DAIFMT_NB_IF:
        case SND_SOC_DAIFMT_IB_IF:
                if (!frame_start_falling_edge)
                        mode |= BCM2835_I2S_FSI;
                break;
        default:
                return -EINVAL;
        }

        regmap_write(dev->i2s_regmap, BCM2835_I2S_MODE_A_REG, mode);

        /* Setup the DMA parameters */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_RXTHR(1)
                        | BCM2835_I2S_TXTHR(1)
                        | BCM2835_I2S_DMAEN, 0xffffffff);

        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_DREQ_A_REG,
                          BCM2835_I2S_TX_PANIC(0x10)
                        | BCM2835_I2S_RX_PANIC(0x30)
                        | BCM2835_I2S_TX(0x30)
                        | BCM2835_I2S_RX(0x20), 0xffffffff);

        /* Clear FIFOs */
        bcm2835_i2s_clear_fifos(dev, true, true);

        dev_dbg(dev->dev,
                "slots: %d width: %d rx mask: 0x%02x tx_mask: 0x%02x\n",
                slots, slot_width, rx_mask, tx_mask);

        dev_dbg(dev->dev, "frame len: %d sync len: %d data len: %d\n",
                frame_length, framesync_length, data_length);

        dev_dbg(dev->dev, "rx pos: %d,%d tx pos: %d,%d\n",
                rx_ch1_pos, rx_ch2_pos, tx_ch1_pos, tx_ch2_pos);

        dev_dbg(dev->dev, "sampling rate: %d bclk rate: %d\n",
                params_rate(params), bclk_rate);

        dev_dbg(dev->dev, "CLKM: %d CLKI: %d FSM: %d FSI: %d frame start: %s edge\n",
                !!(mode & BCM2835_I2S_CLKM),
                !!(mode & BCM2835_I2S_CLKI),
                !!(mode & BCM2835_I2S_FSM),
                !!(mode & BCM2835_I2S_FSI),
                (mode & BCM2835_I2S_FSI) ? "falling" : "rising");

        return ret;
}

static int bcm2835_i2s_prepare(struct snd_pcm_substream *substream,
                struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
        uint32_t cs_reg;

        /*
         * Clear both FIFOs if the one that should be started
         * is not empty at the moment. This should only happen
         * after overrun. Otherwise, hw_params would have cleared
         * the FIFO.
         */
        regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &cs_reg);

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK
                        && !(cs_reg & BCM2835_I2S_TXE))
                bcm2835_i2s_clear_fifos(dev, true, false);
        else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE
                        && (cs_reg & BCM2835_I2S_RXD))
                bcm2835_i2s_clear_fifos(dev, false, true);

        return 0;
}

static void bcm2835_i2s_stop(struct bcm2835_i2s_dev *dev,
                struct snd_pcm_substream *substream,
                struct snd_soc_dai *dai)
{
        uint32_t mask;

        if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
                mask = BCM2835_I2S_RXON;
        else
                mask = BCM2835_I2S_TXON;

        regmap_update_bits(dev->i2s_regmap,
                        BCM2835_I2S_CS_A_REG, mask, 0);

        /* Stop also the clock when not SND_SOC_DAIFMT_CONT */
        if (!dai->active && !(dev->fmt & SND_SOC_DAIFMT_CONT))
                bcm2835_i2s_stop_clock(dev);
}

static int bcm2835_i2s_trigger(struct snd_pcm_substream *substream, int cmd,
                               struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
        uint32_t mask;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
        case SNDRV_PCM_TRIGGER_RESUME:
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
                bcm2835_i2s_start_clock(dev);

                if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
                        mask = BCM2835_I2S_RXON;
                else
                        mask = BCM2835_I2S_TXON;

                regmap_update_bits(dev->i2s_regmap,
                                BCM2835_I2S_CS_A_REG, mask, mask);
                break;

        case SNDRV_PCM_TRIGGER_STOP:
        case SNDRV_PCM_TRIGGER_SUSPEND:
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
                bcm2835_i2s_stop(dev, substream, dai);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int bcm2835_i2s_startup(struct snd_pcm_substream *substream,
                               struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);

        if (dai->active)
                return 0;

        /* Should this still be running stop it */
        bcm2835_i2s_stop_clock(dev);

        /* Enable PCM block */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_EN, BCM2835_I2S_EN);

        /*
         * Disable STBY.
         * Requires at least 4 PCM clock cycles to take effect.
         */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_STBY, BCM2835_I2S_STBY);

        return 0;
}

static void bcm2835_i2s_shutdown(struct snd_pcm_substream *substream,
                struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);

        bcm2835_i2s_stop(dev, substream, dai);

        /* If both streams are stopped, disable module and clock */
        if (dai->active)
                return;

        /* Disable the module */
        regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
                        BCM2835_I2S_EN, 0);

        /*
         * Stopping clock is necessary, because stop does
         * not stop the clock when SND_SOC_DAIFMT_CONT
         */
        bcm2835_i2s_stop_clock(dev);
}

static const struct snd_soc_dai_ops bcm2835_i2s_dai_ops = {
        .startup        = bcm2835_i2s_startup,
        .shutdown       = bcm2835_i2s_shutdown,
        .prepare        = bcm2835_i2s_prepare,
        .trigger        = bcm2835_i2s_trigger,
        .hw_params      = bcm2835_i2s_hw_params,
        .set_fmt        = bcm2835_i2s_set_dai_fmt,
        .set_bclk_ratio = bcm2835_i2s_set_dai_bclk_ratio,
        .set_tdm_slot   = bcm2835_i2s_set_dai_tdm_slot,
};

static int bcm2835_i2s_dai_probe(struct snd_soc_dai *dai)
{
        struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);

        snd_soc_dai_init_dma_data(dai,
                        &dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK],
                        &dev->dma_data[SNDRV_PCM_STREAM_CAPTURE]);

        return 0;
}

static struct snd_soc_dai_driver bcm2835_i2s_dai = {
        .name   = "bcm2835-i2s",
        .probe  = bcm2835_i2s_dai_probe,
        .playback = {
                .channels_min = 2,
                .channels_max = 2,
                .rates =        SNDRV_PCM_RATE_CONTINUOUS,
                .rate_min =     8000,
                .rate_max =     384000,
                .formats =      SNDRV_PCM_FMTBIT_S16_LE
                                | SNDRV_PCM_FMTBIT_S24_LE
                                | SNDRV_PCM_FMTBIT_S32_LE
                },
        .capture = {
                .channels_min = 2,
                .channels_max = 2,
                .rates =        SNDRV_PCM_RATE_CONTINUOUS,
                .rate_min =     8000,
                .rate_max =     384000,
                .formats =      SNDRV_PCM_FMTBIT_S16_LE
                                | SNDRV_PCM_FMTBIT_S24_LE
                                | SNDRV_PCM_FMTBIT_S32_LE
                },
        .ops = &bcm2835_i2s_dai_ops,
        .symmetric_rates = 1,
        .symmetric_samplebits = 1,
};

static bool bcm2835_i2s_volatile_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case BCM2835_I2S_CS_A_REG:
        case BCM2835_I2S_FIFO_A_REG:
        case BCM2835_I2S_INTSTC_A_REG:
        case BCM2835_I2S_GRAY_REG:
                return true;
        default:
                return false;
        };
}

static bool bcm2835_i2s_precious_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case BCM2835_I2S_FIFO_A_REG:
                return true;
        default:
                return false;
        };
}

static const struct regmap_config bcm2835_regmap_config = {
        .reg_bits = 32,
        .reg_stride = 4,
        .val_bits = 32,
        .max_register = BCM2835_I2S_GRAY_REG,
        .precious_reg = bcm2835_i2s_precious_reg,
        .volatile_reg = bcm2835_i2s_volatile_reg,
        .cache_type = REGCACHE_RBTREE,
};

static const struct snd_soc_component_driver bcm2835_i2s_component = {
        .name           = "bcm2835-i2s-comp",
};

static int bcm2835_i2s_probe(struct platform_device *pdev)
{
        struct bcm2835_i2s_dev *dev;
        int ret;
        struct resource *mem;
        void __iomem *base;
        const __be32 *addr;
        dma_addr_t dma_base;

        dev = devm_kzalloc(&pdev->dev, sizeof(*dev),
                           GFP_KERNEL);
        if (!dev)
                return -ENOMEM;

        /* get the clock */
        dev->clk_prepared = false;
        dev->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(dev->clk)) {
                dev_err(&pdev->dev, "could not get clk: %ld\n",
                        PTR_ERR(dev->clk));
                return PTR_ERR(dev->clk);
        }

        /* Request ioarea */
        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        base = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(base))
                return PTR_ERR(base);

        dev->i2s_regmap = devm_regmap_init_mmio(&pdev->dev, base,
                                &bcm2835_regmap_config);
        if (IS_ERR(dev->i2s_regmap))
                return PTR_ERR(dev->i2s_regmap);

        /* Set the DMA address - we have to parse DT ourselves */
        addr = of_get_address(pdev->dev.of_node, 0, NULL, NULL);
        if (!addr) {
                dev_err(&pdev->dev, "could not get DMA-register address\n");
                return -EINVAL;
        }
        dma_base = be32_to_cpup(addr);

        dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].addr =
                dma_base + BCM2835_I2S_FIFO_A_REG;

        dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].addr =
                dma_base + BCM2835_I2S_FIFO_A_REG;

        /* Set the bus width */
        dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].addr_width =
                DMA_SLAVE_BUSWIDTH_4_BYTES;
        dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].addr_width =
                DMA_SLAVE_BUSWIDTH_4_BYTES;

        /* Set burst */
        dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].maxburst = 2;
        dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].maxburst = 2;

        /*
         * Set the PACK flag to enable S16_LE support (2 S16_LE values
         * packed into 32-bit transfers).
         */
        dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].flags =
                SND_DMAENGINE_PCM_DAI_FLAG_PACK;
        dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].flags =
                SND_DMAENGINE_PCM_DAI_FLAG_PACK;

        /* Store the pdev */
        dev->dev = &pdev->dev;
        dev_set_drvdata(&pdev->dev, dev);

        ret = devm_snd_soc_register_component(&pdev->dev,
                        &bcm2835_i2s_component, &bcm2835_i2s_dai, 1);
        if (ret) {
                dev_err(&pdev->dev, "Could not register DAI: %d\n", ret);
                return ret;
        }

        ret = devm_snd_dmaengine_pcm_register(&pdev->dev, NULL, 0);
        if (ret) {
                dev_err(&pdev->dev, "Could not register PCM: %d\n", ret);
                return ret;
        }

        return 0;
}

static const struct of_device_id bcm2835_i2s_of_match[] = {
        { .compatible = "brcm,bcm2835-i2s", },
        {},
};

MODULE_DEVICE_TABLE(of, bcm2835_i2s_of_match);

static struct platform_driver bcm2835_i2s_driver = {
        .probe          = bcm2835_i2s_probe,
        .driver         = {
                .name   = "bcm2835-i2s",
                .of_match_table = bcm2835_i2s_of_match,
        },
};

module_platform_driver(bcm2835_i2s_driver);

MODULE_ALIAS("platform:bcm2835-i2s");
MODULE_DESCRIPTION("BCM2835 I2S interface");
MODULE_AUTHOR("Florian Meier <florian.meier@koalo.de>");
MODULE_LICENSE("GPL v2");