[mirror_ubuntu-bionic-kernel.git] / sound / soc / davinci / davinci-pcm.c

/*
 * ALSA PCM interface for the TI DAVINCI processor
 *
 * Author:      Vladimir Barinov, <vbarinov@embeddedalley.com>
 * Copyright:   (C) 2007 MontaVista Software, Inc., <source@mvista.com>
 * added SRAM ping/pong (C) 2008 Troy Kisky <troy.kisky@boundarydevices.com>
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/dma-mapping.h>
#include <linux/kernel.h>
#include <linux/genalloc.h>
#include <linux/platform_data/edma.h>

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

#include <asm/dma.h>

#include "davinci-pcm.h"

#ifdef DEBUG
static void print_buf_info(int slot, char *name)
{
        struct edmacc_param p;
        if (slot < 0)
                return;
        edma_read_slot(slot, &p);
        printk(KERN_DEBUG "%s: 0x%x, opt=%x, src=%x, a_b_cnt=%x dst=%x\n",
                        name, slot, p.opt, p.src, p.a_b_cnt, p.dst);
        printk(KERN_DEBUG "    src_dst_bidx=%x link_bcntrld=%x src_dst_cidx=%x ccnt=%x\n",
                        p.src_dst_bidx, p.link_bcntrld, p.src_dst_cidx, p.ccnt);
}
#else
static void print_buf_info(int slot, char *name)
{
}
#endif

#define DAVINCI_PCM_FMTBITS     (\
                                SNDRV_PCM_FMTBIT_S8     |\
                                SNDRV_PCM_FMTBIT_U8     |\
                                SNDRV_PCM_FMTBIT_S16_LE |\
                                SNDRV_PCM_FMTBIT_S16_BE |\
                                SNDRV_PCM_FMTBIT_U16_LE |\
                                SNDRV_PCM_FMTBIT_U16_BE |\
                                SNDRV_PCM_FMTBIT_S24_LE |\
                                SNDRV_PCM_FMTBIT_S24_BE |\
                                SNDRV_PCM_FMTBIT_U24_LE |\
                                SNDRV_PCM_FMTBIT_U24_BE |\
                                SNDRV_PCM_FMTBIT_S32_LE |\
                                SNDRV_PCM_FMTBIT_S32_BE |\
                                SNDRV_PCM_FMTBIT_U32_LE |\
                                SNDRV_PCM_FMTBIT_U32_BE)

static struct snd_pcm_hardware pcm_hardware_playback = {
        .info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER |
                 SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
                 SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME|
                 SNDRV_PCM_INFO_BATCH),
        .formats = DAVINCI_PCM_FMTBITS,
        .rates = SNDRV_PCM_RATE_8000_192000 | SNDRV_PCM_RATE_KNOT,
        .rate_min = 8000,
        .rate_max = 192000,
        .channels_min = 2,
        .channels_max = 384,
        .buffer_bytes_max = 128 * 1024,
        .period_bytes_min = 32,
        .period_bytes_max = 8 * 1024,
        .periods_min = 16,
        .periods_max = 255,
        .fifo_size = 0,
};

static struct snd_pcm_hardware pcm_hardware_capture = {
        .info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER |
                 SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
                 SNDRV_PCM_INFO_PAUSE |
                 SNDRV_PCM_INFO_BATCH),
        .formats = DAVINCI_PCM_FMTBITS,
        .rates = SNDRV_PCM_RATE_8000_192000 | SNDRV_PCM_RATE_KNOT,
        .rate_min = 8000,
        .rate_max = 192000,
        .channels_min = 2,
        .channels_max = 384,
        .buffer_bytes_max = 128 * 1024,
        .period_bytes_min = 32,
        .period_bytes_max = 8 * 1024,
        .periods_min = 16,
        .periods_max = 255,
        .fifo_size = 0,
};

/*
 * How ping/pong works....
 *
 * Playback:
 * ram_params - copys 2*ping_size from start of SDRAM to iram,
 *      links to ram_link2
 * ram_link2 - copys rest of SDRAM to iram in ping_size units,
 *      links to ram_link
 * ram_link - copys entire SDRAM to iram in ping_size uints,
 *      links to self
 *
 * asp_params - same as asp_link[0]
 * asp_link[0] - copys from lower half of iram to asp port
 *      links to asp_link[1], triggers iram copy event on completion
 * asp_link[1] - copys from upper half of iram to asp port
 *      links to asp_link[0], triggers iram copy event on completion
 *      triggers interrupt only needed to let upper SOC levels update position
 *      in stream on completion
 *
 * When playback is started:
 *      ram_params started
 *      asp_params started
 *
 * Capture:
 * ram_params - same as ram_link,
 *      links to ram_link
 * ram_link - same as playback
 *      links to self
 *
 * asp_params - same as playback
 * asp_link[0] - same as playback
 * asp_link[1] - same as playback
 *
 * When capture is started:
 *      asp_params started
 */
struct davinci_runtime_data {
        spinlock_t lock;
        int period;             /* current DMA period */
        int asp_channel;        /* Master DMA channel */
        int asp_link[2];        /* asp parameter link channel, ping/pong */
        struct davinci_pcm_dma_params *params;  /* DMA params */
        int ram_channel;
        int ram_link;
        int ram_link2;
        struct edmacc_param asp_params;
        struct edmacc_param ram_params;
};

static void davinci_pcm_period_elapsed(struct snd_pcm_substream *substream)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;
        struct snd_pcm_runtime *runtime = substream->runtime;

        prtd->period++;
        if (unlikely(prtd->period >= runtime->periods))
                prtd->period = 0;
}

static void davinci_pcm_period_reset(struct snd_pcm_substream *substream)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;

        prtd->period = 0;
}
/*
 * Not used with ping/pong
 */
static void davinci_pcm_enqueue_dma(struct snd_pcm_substream *substream)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;
        struct snd_pcm_runtime *runtime = substream->runtime;
        unsigned int period_size;
        unsigned int dma_offset;
        dma_addr_t dma_pos;
        dma_addr_t src, dst;
        unsigned short src_bidx, dst_bidx;
        unsigned short src_cidx, dst_cidx;
        unsigned int data_type;
        unsigned short acnt;
        unsigned int count;
        unsigned int fifo_level;

        period_size = snd_pcm_lib_period_bytes(substream);
        dma_offset = prtd->period * period_size;
        dma_pos = runtime->dma_addr + dma_offset;
        fifo_level = prtd->params->fifo_level;

        pr_debug("davinci_pcm: audio_set_dma_params_play channel = %d "
                "dma_ptr = %x period_size=%x\n", prtd->asp_link[0], dma_pos,
                period_size);

        data_type = prtd->params->data_type;
        count = period_size / data_type;
        if (fifo_level)
                count /= fifo_level;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                src = dma_pos;
                dst = prtd->params->dma_addr;
                src_bidx = data_type;
                dst_bidx = 4;
                src_cidx = data_type * fifo_level;
                dst_cidx = 0;
        } else {
                src = prtd->params->dma_addr;
                dst = dma_pos;
                src_bidx = 0;
                dst_bidx = data_type;
                src_cidx = 0;
                dst_cidx = data_type * fifo_level;
        }

        acnt = prtd->params->acnt;
        edma_set_src(prtd->asp_link[0], src, INCR, W8BIT);
        edma_set_dest(prtd->asp_link[0], dst, INCR, W8BIT);

        edma_set_src_index(prtd->asp_link[0], src_bidx, src_cidx);
        edma_set_dest_index(prtd->asp_link[0], dst_bidx, dst_cidx);

        if (!fifo_level)
                edma_set_transfer_params(prtd->asp_link[0], acnt, count, 1, 0,
                                                        ASYNC);
        else
                edma_set_transfer_params(prtd->asp_link[0], acnt,
                                                fifo_level,
                                                count, fifo_level,
                                                ABSYNC);
}

static void davinci_pcm_dma_irq(unsigned link, u16 ch_status, void *data)
{
        struct snd_pcm_substream *substream = data;
        struct davinci_runtime_data *prtd = substream->runtime->private_data;

        print_buf_info(prtd->ram_channel, "i ram_channel");
        pr_debug("davinci_pcm: link=%d, status=0x%x\n", link, ch_status);

        if (unlikely(ch_status != DMA_COMPLETE))
                return;

        if (snd_pcm_running(substream)) {
                spin_lock(&prtd->lock);
                if (prtd->ram_channel < 0) {
                        /* No ping/pong must fix up link dma data*/
                        davinci_pcm_enqueue_dma(substream);
                }
                davinci_pcm_period_elapsed(substream);
                spin_unlock(&prtd->lock);
                snd_pcm_period_elapsed(substream);
        }
}

#ifdef CONFIG_GENERIC_ALLOCATOR
static int allocate_sram(struct snd_pcm_substream *substream,
                struct gen_pool *sram_pool, unsigned size,
                struct snd_pcm_hardware *ppcm)
{
        struct snd_dma_buffer *buf = &substream->dma_buffer;
        struct snd_dma_buffer *iram_dma = NULL;
        dma_addr_t iram_phys = 0;
        void *iram_virt = NULL;

        if (buf->private_data || !size)
                return 0;

        ppcm->period_bytes_max = size;
        iram_virt = (void *)gen_pool_alloc(sram_pool, size);
        if (!iram_virt)
                goto exit1;
        iram_phys = gen_pool_virt_to_phys(sram_pool, (unsigned)iram_virt);
        iram_dma = kzalloc(sizeof(*iram_dma), GFP_KERNEL);
        if (!iram_dma)
                goto exit2;
        iram_dma->area = iram_virt;
        iram_dma->addr = iram_phys;
        memset(iram_dma->area, 0, size);
        iram_dma->bytes = size;
        buf->private_data = iram_dma;
        return 0;
exit2:
        if (iram_virt)
                gen_pool_free(sram_pool, (unsigned)iram_virt, size);
exit1:
        return -ENOMEM;
}

static void davinci_free_sram(struct snd_pcm_substream *substream,
                              struct snd_dma_buffer *iram_dma)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;
        struct gen_pool *sram_pool = prtd->params->sram_pool;

        gen_pool_free(sram_pool, (unsigned) iram_dma->area, iram_dma->bytes);
}
#else
static int allocate_sram(struct snd_pcm_substream *substream,
                struct gen_pool *sram_pool, unsigned size,
                struct snd_pcm_hardware *ppcm)
{
        return 0;
}

static void davinci_free_sram(struct snd_pcm_substream *substream,
                              struct snd_dma_buffer *iram_dma)
{
}
#endif

/*
 * Only used with ping/pong.
 * This is called after runtime->dma_addr, period_bytes and data_type are valid
 */
static int ping_pong_dma_setup(struct snd_pcm_substream *substream)
{
        unsigned short ram_src_cidx, ram_dst_cidx;
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct davinci_runtime_data *prtd = runtime->private_data;
        struct snd_dma_buffer *iram_dma =
                (struct snd_dma_buffer *)substream->dma_buffer.private_data;
        struct davinci_pcm_dma_params *params = prtd->params;
        unsigned int data_type = params->data_type;
        unsigned int acnt = params->acnt;
        /* divide by 2 for ping/pong */
        unsigned int ping_size = snd_pcm_lib_period_bytes(substream) >> 1;
        unsigned int fifo_level = prtd->params->fifo_level;
        unsigned int count;
        if ((data_type == 0) || (data_type > 4)) {
                printk(KERN_ERR "%s: data_type=%i\n", __func__, data_type);
                return -EINVAL;
        }
        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                dma_addr_t asp_src_pong = iram_dma->addr + ping_size;
                ram_src_cidx = ping_size;
                ram_dst_cidx = -ping_size;
                edma_set_src(prtd->asp_link[1], asp_src_pong, INCR, W8BIT);

                edma_set_src_index(prtd->asp_link[0], data_type,
                                data_type * fifo_level);
                edma_set_src_index(prtd->asp_link[1], data_type,
                                data_type * fifo_level);

                edma_set_src(prtd->ram_link, runtime->dma_addr, INCR, W32BIT);
        } else {
                dma_addr_t asp_dst_pong = iram_dma->addr + ping_size;
                ram_src_cidx = -ping_size;
                ram_dst_cidx = ping_size;
                edma_set_dest(prtd->asp_link[1], asp_dst_pong, INCR, W8BIT);

                edma_set_dest_index(prtd->asp_link[0], data_type,
                                data_type * fifo_level);
                edma_set_dest_index(prtd->asp_link[1], data_type,
                                data_type * fifo_level);

                edma_set_dest(prtd->ram_link, runtime->dma_addr, INCR, W32BIT);
        }

        if (!fifo_level) {
                count = ping_size / data_type;
                edma_set_transfer_params(prtd->asp_link[0], acnt, count,
                                1, 0, ASYNC);
                edma_set_transfer_params(prtd->asp_link[1], acnt, count,
                                1, 0, ASYNC);
        } else {
                count = ping_size / (data_type * fifo_level);
                edma_set_transfer_params(prtd->asp_link[0], acnt, fifo_level,
                                count, fifo_level, ABSYNC);
                edma_set_transfer_params(prtd->asp_link[1], acnt, fifo_level,
                                count, fifo_level, ABSYNC);
        }

        edma_set_src_index(prtd->ram_link, ping_size, ram_src_cidx);
        edma_set_dest_index(prtd->ram_link, ping_size, ram_dst_cidx);
        edma_set_transfer_params(prtd->ram_link, ping_size, 2,
                        runtime->periods, 2, ASYNC);

        /* init master params */
        edma_read_slot(prtd->asp_link[0], &prtd->asp_params);
        edma_read_slot(prtd->ram_link, &prtd->ram_params);
        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                struct edmacc_param p_ram;
                /* Copy entire iram buffer before playback started */
                prtd->ram_params.a_b_cnt = (1 << 16) | (ping_size << 1);
                /* 0 dst_bidx */
                prtd->ram_params.src_dst_bidx = (ping_size << 1);
                /* 0 dst_cidx */
                prtd->ram_params.src_dst_cidx = (ping_size << 1);
                prtd->ram_params.ccnt = 1;

                /* Skip 1st period */
                edma_read_slot(prtd->ram_link, &p_ram);
                p_ram.src += (ping_size << 1);
                p_ram.ccnt -= 1;
                edma_write_slot(prtd->ram_link2, &p_ram);
                /*
                 * When 1st started, ram -> iram dma channel will fill the
                 * entire iram.  Then, whenever a ping/pong asp buffer finishes,
                 * 1/2 iram will be filled.
                 */
                prtd->ram_params.link_bcntrld =
                        EDMA_CHAN_SLOT(prtd->ram_link2) << 5;
        }
        return 0;
}

/* 1 asp tx or rx channel using 2 parameter channels
 * 1 ram to/from iram channel using 1 parameter channel
 *
 * Playback
 * ram copy channel kicks off first,
 * 1st ram copy of entire iram buffer completion kicks off asp channel
 * asp tcc always kicks off ram copy of 1/2 iram buffer
 *
 * Record
 * asp channel starts, tcc kicks off ram copy
 */
static int request_ping_pong(struct snd_pcm_substream *substream,
                struct davinci_runtime_data *prtd,
                struct snd_dma_buffer *iram_dma)
{
        dma_addr_t asp_src_ping;
        dma_addr_t asp_dst_ping;
        int ret;
        struct davinci_pcm_dma_params *params = prtd->params;

        /* Request ram master channel */
        ret = prtd->ram_channel = edma_alloc_channel(EDMA_CHANNEL_ANY,
                                  davinci_pcm_dma_irq, substream,
                                  prtd->params->ram_chan_q);
        if (ret < 0)
                goto exit1;

        /* Request ram link channel */
        ret = prtd->ram_link = edma_alloc_slot(
                        EDMA_CTLR(prtd->ram_channel), EDMA_SLOT_ANY);
        if (ret < 0)
                goto exit2;

        ret = prtd->asp_link[1] = edma_alloc_slot(
                        EDMA_CTLR(prtd->asp_channel), EDMA_SLOT_ANY);
        if (ret < 0)
                goto exit3;

        prtd->ram_link2 = -1;
        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                ret = prtd->ram_link2 = edma_alloc_slot(
                        EDMA_CTLR(prtd->ram_channel), EDMA_SLOT_ANY);
                if (ret < 0)
                        goto exit4;
        }
        /* circle ping-pong buffers */
        edma_link(prtd->asp_link[0], prtd->asp_link[1]);
        edma_link(prtd->asp_link[1], prtd->asp_link[0]);
        /* circle ram buffers */
        edma_link(prtd->ram_link, prtd->ram_link);

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                asp_src_ping = iram_dma->addr;
                asp_dst_ping = params->dma_addr;        /* fifo */
        } else {
                asp_src_ping = params->dma_addr;        /* fifo */
                asp_dst_ping = iram_dma->addr;
        }
        /* ping */
        edma_set_src(prtd->asp_link[0], asp_src_ping, INCR, W16BIT);
        edma_set_dest(prtd->asp_link[0], asp_dst_ping, INCR, W16BIT);
        edma_set_src_index(prtd->asp_link[0], 0, 0);
        edma_set_dest_index(prtd->asp_link[0], 0, 0);

        edma_read_slot(prtd->asp_link[0], &prtd->asp_params);
        prtd->asp_params.opt &= ~(TCCMODE | EDMA_TCC(0x3f) | TCINTEN);
        prtd->asp_params.opt |= TCCHEN |
                EDMA_TCC(prtd->ram_channel & 0x3f);
        edma_write_slot(prtd->asp_link[0], &prtd->asp_params);

        /* pong */
        edma_set_src(prtd->asp_link[1], asp_src_ping, INCR, W16BIT);
        edma_set_dest(prtd->asp_link[1], asp_dst_ping, INCR, W16BIT);
        edma_set_src_index(prtd->asp_link[1], 0, 0);
        edma_set_dest_index(prtd->asp_link[1], 0, 0);

        edma_read_slot(prtd->asp_link[1], &prtd->asp_params);
        prtd->asp_params.opt &= ~(TCCMODE | EDMA_TCC(0x3f));
        /* interrupt after every pong completion */
        prtd->asp_params.opt |= TCINTEN | TCCHEN |
                EDMA_TCC(prtd->ram_channel & 0x3f);
        edma_write_slot(prtd->asp_link[1], &prtd->asp_params);

        /* ram */
        edma_set_src(prtd->ram_link, iram_dma->addr, INCR, W32BIT);
        edma_set_dest(prtd->ram_link, iram_dma->addr, INCR, W32BIT);
        pr_debug("%s: audio dma channels/slots in use for ram:%u %u %u,"
                "for asp:%u %u %u\n", __func__,
                prtd->ram_channel, prtd->ram_link, prtd->ram_link2,
                prtd->asp_channel, prtd->asp_link[0],
                prtd->asp_link[1]);
        return 0;
exit4:
        edma_free_channel(prtd->asp_link[1]);
        prtd->asp_link[1] = -1;
exit3:
        edma_free_channel(prtd->ram_link);
        prtd->ram_link = -1;
exit2:
        edma_free_channel(prtd->ram_channel);
        prtd->ram_channel = -1;
exit1:
        return ret;
}

static int davinci_pcm_dma_request(struct snd_pcm_substream *substream)
{
        struct snd_dma_buffer *iram_dma;
        struct davinci_runtime_data *prtd = substream->runtime->private_data;
        struct davinci_pcm_dma_params *params = prtd->params;
        int ret;

        if (!params)
                return -ENODEV;

        /* Request asp master DMA channel */
        ret = prtd->asp_channel = edma_alloc_channel(params->channel,
                        davinci_pcm_dma_irq, substream,
                        prtd->params->asp_chan_q);
        if (ret < 0)
                goto exit1;

        /* Request asp link channels */
        ret = prtd->asp_link[0] = edma_alloc_slot(
                        EDMA_CTLR(prtd->asp_channel), EDMA_SLOT_ANY);
        if (ret < 0)
                goto exit2;

        iram_dma = (struct snd_dma_buffer *)substream->dma_buffer.private_data;
        if (iram_dma) {
                if (request_ping_pong(substream, prtd, iram_dma) == 0)
                        return 0;
                printk(KERN_WARNING "%s: dma channel allocation failed,"
                                "not using sram\n", __func__);
        }

        /* Issue transfer completion IRQ when the channel completes a
         * transfer, then always reload from the same slot (by a kind
         * of loopback link).  The completion IRQ handler will update
         * the reload slot with a new buffer.
         *
         * REVISIT save p_ram here after setting up everything except
         * the buffer and its length (ccnt) ... use it as a template
         * so davinci_pcm_enqueue_dma() takes less time in IRQ.
         */
        edma_read_slot(prtd->asp_link[0], &prtd->asp_params);
        prtd->asp_params.opt |= TCINTEN |
                EDMA_TCC(EDMA_CHAN_SLOT(prtd->asp_channel));
        prtd->asp_params.link_bcntrld = EDMA_CHAN_SLOT(prtd->asp_link[0]) << 5;
        edma_write_slot(prtd->asp_link[0], &prtd->asp_params);
        return 0;
exit2:
        edma_free_channel(prtd->asp_channel);
        prtd->asp_channel = -1;
exit1:
        return ret;
}

static int davinci_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;
        int ret = 0;

        spin_lock(&prtd->lock);

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                edma_start(prtd->asp_channel);
                if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
                    prtd->ram_channel >= 0) {
                        /* copy 1st iram buffer */
                        edma_start(prtd->ram_channel);
                }
                break;
        case SNDRV_PCM_TRIGGER_RESUME:
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
                edma_resume(prtd->asp_channel);
                break;
        case SNDRV_PCM_TRIGGER_STOP:
        case SNDRV_PCM_TRIGGER_SUSPEND:
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
                edma_pause(prtd->asp_channel);
                break;
        default:
                ret = -EINVAL;
                break;
        }

        spin_unlock(&prtd->lock);

        return ret;
}

static int davinci_pcm_prepare(struct snd_pcm_substream *substream)
{
        struct davinci_runtime_data *prtd = substream->runtime->private_data;

        davinci_pcm_period_reset(substream);
        if (prtd->ram_channel >= 0) {
                int ret = ping_pong_dma_setup(substream);
                if (ret < 0)
                        return ret;

                edma_write_slot(prtd->ram_channel, &prtd->ram_params);
                edma_write_slot(prtd->asp_channel, &prtd->asp_params);

                print_buf_info(prtd->ram_channel, "ram_channel");
                print_buf_info(prtd->ram_link, "ram_link");
                print_buf_info(prtd->ram_link2, "ram_link2");
                print_buf_info(prtd->asp_channel, "asp_channel");
                print_buf_info(prtd->asp_link[0], "asp_link[0]");
                print_buf_info(prtd->asp_link[1], "asp_link[1]");

                /*
                 * There is a phase offset of 2 periods between the position
                 * used by dma setup and the position reported in the pointer
                 * function.
                 *
                 * The phase offset, when not using ping-pong buffers, is due to
                 * the two consecutive calls to davinci_pcm_enqueue_dma() below.
                 *
                 * Whereas here, with ping-pong buffers, the phase is due to
                 * there being an entire buffer transfer complete before the
                 * first dma completion event triggers davinci_pcm_dma_irq().
                 */
                davinci_pcm_period_elapsed(substream);
                davinci_pcm_period_elapsed(substream);

                return 0;
        }
        davinci_pcm_enqueue_dma(substream);
        davinci_pcm_period_elapsed(substream);

        /* Copy self-linked parameter RAM entry into master channel */
        edma_read_slot(prtd->asp_link[0], &prtd->asp_params);
        edma_write_slot(prtd->asp_channel, &prtd->asp_params);
        davinci_pcm_enqueue_dma(substream);
        davinci_pcm_period_elapsed(substream);

        return 0;
}

static snd_pcm_uframes_t
davinci_pcm_pointer(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct davinci_runtime_data *prtd = runtime->private_data;
        unsigned int offset;
        int asp_count;
        unsigned int period_size = snd_pcm_lib_period_bytes(substream);

        /*
         * There is a phase offset of 2 periods between the position used by dma
         * setup and the position reported in the pointer function. Either +2 in
         * the dma setup or -2 here in the pointer function (with wrapping,
         * both) accounts for this offset -- choose the latter since it makes
         * the first-time setup clearer.
         */
        spin_lock(&prtd->lock);
        asp_count = prtd->period - 2;
        spin_unlock(&prtd->lock);

        if (asp_count < 0)
                asp_count += runtime->periods;
        asp_count *= period_size;

        offset = bytes_to_frames(runtime, asp_count);
        if (offset >= runtime->buffer_size)
                offset = 0;

        return offset;
}

static int davinci_pcm_open(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct davinci_runtime_data *prtd;
        struct snd_pcm_hardware *ppcm;
        int ret = 0;
        struct snd_soc_pcm_runtime *rtd = substream->private_data;
        struct davinci_pcm_dma_params *pa;
        struct davinci_pcm_dma_params *params;

        pa = snd_soc_dai_get_dma_data(rtd->cpu_dai, substream);
        if (!pa)
                return -ENODEV;
        params = &pa[substream->stream];

        ppcm = (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) ?
                        &pcm_hardware_playback : &pcm_hardware_capture;
        allocate_sram(substream, params->sram_pool, params->sram_size, ppcm);
        snd_soc_set_runtime_hwparams(substream, ppcm);
        /* ensure that buffer size is a multiple of period size */
        ret = snd_pcm_hw_constraint_integer(runtime,
                                                SNDRV_PCM_HW_PARAM_PERIODS);
        if (ret < 0)
                return ret;

        prtd = kzalloc(sizeof(struct davinci_runtime_data), GFP_KERNEL);
        if (prtd == NULL)
                return -ENOMEM;

        spin_lock_init(&prtd->lock);
        prtd->params = params;
        prtd->asp_channel = -1;
        prtd->asp_link[0] = prtd->asp_link[1] = -1;
        prtd->ram_channel = -1;
        prtd->ram_link = -1;
        prtd->ram_link2 = -1;

        runtime->private_data = prtd;

        ret = davinci_pcm_dma_request(substream);
        if (ret) {
                printk(KERN_ERR "davinci_pcm: Failed to get dma channels\n");
                kfree(prtd);
        }

        return ret;
}

static int davinci_pcm_close(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct davinci_runtime_data *prtd = runtime->private_data;

        if (prtd->ram_channel >= 0)
                edma_stop(prtd->ram_channel);
        if (prtd->asp_channel >= 0)
                edma_stop(prtd->asp_channel);
        if (prtd->asp_link[0] >= 0)
                edma_unlink(prtd->asp_link[0]);
        if (prtd->asp_link[1] >= 0)
                edma_unlink(prtd->asp_link[1]);
        if (prtd->ram_link >= 0)
                edma_unlink(prtd->ram_link);

        if (prtd->asp_link[0] >= 0)
                edma_free_slot(prtd->asp_link[0]);
        if (prtd->asp_link[1] >= 0)
                edma_free_slot(prtd->asp_link[1]);
        if (prtd->asp_channel >= 0)
                edma_free_channel(prtd->asp_channel);
        if (prtd->ram_link >= 0)
                edma_free_slot(prtd->ram_link);
        if (prtd->ram_link2 >= 0)
                edma_free_slot(prtd->ram_link2);
        if (prtd->ram_channel >= 0)
                edma_free_channel(prtd->ram_channel);

        kfree(prtd);

        return 0;
}

static int davinci_pcm_hw_params(struct snd_pcm_substream *substream,
                                 struct snd_pcm_hw_params *hw_params)
{
        return snd_pcm_lib_malloc_pages(substream,
                                        params_buffer_bytes(hw_params));
}

static int davinci_pcm_hw_free(struct snd_pcm_substream *substream)
{
        return snd_pcm_lib_free_pages(substream);
}

static int davinci_pcm_mmap(struct snd_pcm_substream *substream,
                            struct vm_area_struct *vma)
{
        struct snd_pcm_runtime *runtime = substream->runtime;

        return dma_mmap_writecombine(substream->pcm->card->dev, vma,
                                     runtime->dma_area,
                                     runtime->dma_addr,
                                     runtime->dma_bytes);
}

static struct snd_pcm_ops davinci_pcm_ops = {
        .open =         davinci_pcm_open,
        .close =        davinci_pcm_close,
        .ioctl =        snd_pcm_lib_ioctl,
        .hw_params =    davinci_pcm_hw_params,
        .hw_free =      davinci_pcm_hw_free,
        .prepare =      davinci_pcm_prepare,
        .trigger =      davinci_pcm_trigger,
        .pointer =      davinci_pcm_pointer,
        .mmap =         davinci_pcm_mmap,
};

static int davinci_pcm_preallocate_dma_buffer(struct snd_pcm *pcm, int stream,
                size_t size)
{
        struct snd_pcm_substream *substream = pcm->streams[stream].substream;
        struct snd_dma_buffer *buf = &substream->dma_buffer;

        buf->dev.type = SNDRV_DMA_TYPE_DEV;
        buf->dev.dev = pcm->card->dev;
        buf->private_data = NULL;
        buf->area = dma_alloc_writecombine(pcm->card->dev, size,
                                           &buf->addr, GFP_KERNEL);

        pr_debug("davinci_pcm: preallocate_dma_buffer: area=%p, addr=%p, "
                "size=%d\n", (void *) buf->area, (void *) buf->addr, size);

        if (!buf->area)
                return -ENOMEM;

        buf->bytes = size;
        return 0;
}

static void davinci_pcm_free(struct snd_pcm *pcm)
{
        struct snd_pcm_substream *substream;
        struct snd_dma_buffer *buf;
        int stream;

        for (stream = 0; stream < 2; stream++) {
                struct snd_dma_buffer *iram_dma;
                substream = pcm->streams[stream].substream;
                if (!substream)
                        continue;

                buf = &substream->dma_buffer;
                if (!buf->area)
                        continue;

                dma_free_writecombine(pcm->card->dev, buf->bytes,
                                      buf->area, buf->addr);
                buf->area = NULL;
                iram_dma = buf->private_data;
                if (iram_dma) {
                        davinci_free_sram(substream, iram_dma);
                        kfree(iram_dma);
                }
        }
}

static u64 davinci_pcm_dmamask = DMA_BIT_MASK(32);

static int davinci_pcm_new(struct snd_soc_pcm_runtime *rtd)
{
        struct snd_card *card = rtd->card->snd_card;
        struct snd_pcm *pcm = rtd->pcm;
        int ret;

        if (!card->dev->dma_mask)
                card->dev->dma_mask = &davinci_pcm_dmamask;
        if (!card->dev->coherent_dma_mask)
                card->dev->coherent_dma_mask = DMA_BIT_MASK(32);

        if (pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream) {
                ret = davinci_pcm_preallocate_dma_buffer(pcm,
                        SNDRV_PCM_STREAM_PLAYBACK,
                        pcm_hardware_playback.buffer_bytes_max);
                if (ret)
                        return ret;
        }

        if (pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream) {
                ret = davinci_pcm_preallocate_dma_buffer(pcm,
                        SNDRV_PCM_STREAM_CAPTURE,
                        pcm_hardware_capture.buffer_bytes_max);
                if (ret)
                        return ret;
        }

        return 0;
}

static struct snd_soc_platform_driver davinci_soc_platform = {
        .ops =          &davinci_pcm_ops,
        .pcm_new =      davinci_pcm_new,
        .pcm_free =     davinci_pcm_free,
};

int davinci_soc_platform_register(struct device *dev)
{
        return snd_soc_register_platform(dev, &davinci_soc_platform);
}
EXPORT_SYMBOL_GPL(davinci_soc_platform_register);

void davinci_soc_platform_unregister(struct device *dev)
{
        snd_soc_unregister_platform(dev);
}
EXPORT_SYMBOL_GPL(davinci_soc_platform_unregister);

MODULE_AUTHOR("Vladimir Barinov");
MODULE_DESCRIPTION("TI DAVINCI PCM DMA module");
MODULE_LICENSE("GPL");