// SPDX-License-Identifier: GPL-2.0
//
// SH7760 ("camelot") DMABRG audio DMA unit support
//
// Copyright (C) 2007 Manuel Lauss <mano@roarinelk.homelinux.net>
//
// The SH7760 DMABRG provides 4 dma channels (2x rec, 2x play), which
// trigger an interrupt when one half of the programmed transfer size
// has been xmitted.
//
// FIXME: little-endian only for now

#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/dma-mapping.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <sound/soc.h>
#include <asm/dmabrg.h>


/* registers and bits */
#define BRGATXSAR       0x00
#define BRGARXDAR       0x04
#define BRGATXTCR       0x08
#define BRGARXTCR       0x0C
#define BRGACR          0x10
#define BRGATXTCNT      0x14
#define BRGARXTCNT      0x18

#define ACR_RAR         (1 << 18)
#define ACR_RDS         (1 << 17)
#define ACR_RDE         (1 << 16)
#define ACR_TAR         (1 << 2)
#define ACR_TDS         (1 << 1)
#define ACR_TDE         (1 << 0)

/* receiver/transmitter data alignment */
#define ACR_RAM_NONE    (0 << 24)
#define ACR_RAM_4BYTE   (1 << 24)
#define ACR_RAM_2WORD   (2 << 24)
#define ACR_TAM_NONE    (0 << 8)
#define ACR_TAM_4BYTE   (1 << 8)
#define ACR_TAM_2WORD   (2 << 8)


struct camelot_pcm {
        unsigned long mmio;  /* DMABRG audio channel control reg MMIO */
        unsigned int txid;    /* ID of first DMABRG IRQ for this unit */

        struct snd_pcm_substream *tx_ss;
        unsigned long tx_period_size;
        unsigned int  tx_period;

        struct snd_pcm_substream *rx_ss;
        unsigned long rx_period_size;
        unsigned int  rx_period;

} cam_pcm_data[2] = {
        {
                .mmio   =       0xFE3C0040,
                .txid   =       DMABRGIRQ_A0TXF,
        },
        {
                .mmio   =       0xFE3C0060,
                .txid   =       DMABRGIRQ_A1TXF,
        },
};

#define BRGREG(x)       (*(unsigned long *)(cam->mmio + (x)))

/*
 * set a minimum of 16kb per period, to avoid interrupt-"storm" and
 * resulting skipping. In general, the bigger the minimum size, the
 * better for overall system performance. (The SH7760 is a puny CPU
 * with a slow SDRAM interface and poor internal bus bandwidth,
 * *especially* when the LCDC is active).  The minimum for the DMAC
 * is 8 bytes; 16kbytes are enough to get skip-free playback of a
 * 44kHz/16bit/stereo MP3 on a lightly loaded system, and maintain
 * reasonable responsiveness in MPlayer.
 */
#define DMABRG_PERIOD_MIN               16 * 1024
#define DMABRG_PERIOD_MAX               0x03fffffc
#define DMABRG_PREALLOC_BUFFER          32 * 1024
#define DMABRG_PREALLOC_BUFFER_MAX      32 * 1024

static const struct snd_pcm_hardware camelot_pcm_hardware = {
        .info = (SNDRV_PCM_INFO_MMAP |
                SNDRV_PCM_INFO_INTERLEAVED |
                SNDRV_PCM_INFO_BLOCK_TRANSFER |
                SNDRV_PCM_INFO_MMAP_VALID |
                SNDRV_PCM_INFO_BATCH),
        .buffer_bytes_max =     DMABRG_PERIOD_MAX,
        .period_bytes_min =     DMABRG_PERIOD_MIN,
        .period_bytes_max =     DMABRG_PERIOD_MAX / 2,
        .periods_min =          2,
        .periods_max =          2,
        .fifo_size =            128,
};

static void camelot_txdma(void *data)
{
        struct camelot_pcm *cam = data;
        cam->tx_period ^= 1;
        snd_pcm_period_elapsed(cam->tx_ss);
}

static void camelot_rxdma(void *data)
{
        struct camelot_pcm *cam = data;
        cam->rx_period ^= 1;
        snd_pcm_period_elapsed(cam->rx_ss);
}

static int camelot_pcm_open(struct snd_soc_component *component,
                            struct snd_pcm_substream *substream)
{
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];
        int recv = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0:1;
        int ret, dmairq;

        snd_soc_set_runtime_hwparams(substream, &camelot_pcm_hardware);

        /* DMABRG buffer half/full events */
        dmairq = (recv) ? cam->txid + 2 : cam->txid;
        if (recv) {
                cam->rx_ss = substream;
                ret = dmabrg_request_irq(dmairq, camelot_rxdma, cam);
                if (unlikely(ret)) {
                        pr_debug("audio unit %d irqs already taken!\n",
                             asoc_rtd_to_cpu(rtd, 0)->id);
                        return -EBUSY;
                }
                (void)dmabrg_request_irq(dmairq + 1,camelot_rxdma, cam);
        } else {
                cam->tx_ss = substream;
                ret = dmabrg_request_irq(dmairq, camelot_txdma, cam);
                if (unlikely(ret)) {
                        pr_debug("audio unit %d irqs already taken!\n",
                             asoc_rtd_to_cpu(rtd, 0)->id);
                        return -EBUSY;
                }
                (void)dmabrg_request_irq(dmairq + 1, camelot_txdma, cam);
        }
        return 0;
}

static int camelot_pcm_close(struct snd_soc_component *component,
                             struct snd_pcm_substream *substream)
{
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];
        int recv = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0:1;
        int dmairq;

        dmairq = (recv) ? cam->txid + 2 : cam->txid;

        if (recv)
                cam->rx_ss = NULL;
        else
                cam->tx_ss = NULL;

        dmabrg_free_irq(dmairq + 1);
        dmabrg_free_irq(dmairq);

        return 0;
}

static int camelot_hw_params(struct snd_soc_component *component,
                             struct snd_pcm_substream *substream,
                             struct snd_pcm_hw_params *hw_params)
{
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];
        int recv = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0:1;
        int ret;

        if (recv) {
                cam->rx_period_size = params_period_bytes(hw_params);
                cam->rx_period = 0;
        } else {
                cam->tx_period_size = params_period_bytes(hw_params);
                cam->tx_period = 0;
        }
        return 0;
}

static int camelot_prepare(struct snd_soc_component *component,
                           struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];

        pr_debug("PCM data: addr 0x%08lx len %d\n",
                 (u32)runtime->dma_addr, runtime->dma_bytes);
 
        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                BRGREG(BRGATXSAR) = (unsigned long)runtime->dma_area;
                BRGREG(BRGATXTCR) = runtime->dma_bytes;
        } else {
                BRGREG(BRGARXDAR) = (unsigned long)runtime->dma_area;
                BRGREG(BRGARXTCR) = runtime->dma_bytes;
        }

        return 0;
}

static inline void dmabrg_play_dma_start(struct camelot_pcm *cam)
{
        unsigned long acr = BRGREG(BRGACR) & ~(ACR_TDS | ACR_RDS);
        /* start DMABRG engine: XFER start, auto-addr-reload */
        BRGREG(BRGACR) = acr | ACR_TDE | ACR_TAR | ACR_TAM_2WORD;
}

static inline void dmabrg_play_dma_stop(struct camelot_pcm *cam)
{
        unsigned long acr = BRGREG(BRGACR) & ~(ACR_TDS | ACR_RDS);
        /* forcibly terminate data transmission */
        BRGREG(BRGACR) = acr | ACR_TDS;
}

static inline void dmabrg_rec_dma_start(struct camelot_pcm *cam)
{
        unsigned long acr = BRGREG(BRGACR) & ~(ACR_TDS | ACR_RDS);
        /* start DMABRG engine: recv start, auto-reload */
        BRGREG(BRGACR) = acr | ACR_RDE | ACR_RAR | ACR_RAM_2WORD;
}

static inline void dmabrg_rec_dma_stop(struct camelot_pcm *cam)
{
        unsigned long acr = BRGREG(BRGACR) & ~(ACR_TDS | ACR_RDS);
        /* forcibly terminate data receiver */
        BRGREG(BRGACR) = acr | ACR_RDS;
}

static int camelot_trigger(struct snd_soc_component *component,
                           struct snd_pcm_substream *substream, int cmd)
{
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];
        int recv = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0:1;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                if (recv)
                        dmabrg_rec_dma_start(cam);
                else
                        dmabrg_play_dma_start(cam);
                break;
        case SNDRV_PCM_TRIGGER_STOP:
                if (recv)
                        dmabrg_rec_dma_stop(cam);
                else
                        dmabrg_play_dma_stop(cam);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static snd_pcm_uframes_t camelot_pos(struct snd_soc_component *component,
                                     struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
        struct camelot_pcm *cam = &cam_pcm_data[asoc_rtd_to_cpu(rtd, 0)->id];
        int recv = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0:1;
        unsigned long pos;

        /* cannot use the DMABRG pointer register: under load, by the
         * time ALSA comes around to read the register, it is already
         * far ahead (or worse, already done with the fragment) of the
         * position at the time the IRQ was triggered, which results in
         * fast-playback sound in my test application (ScummVM)
         */
        if (recv)
                pos = cam->rx_period ? cam->rx_period_size : 0;
        else
                pos = cam->tx_period ? cam->tx_period_size : 0;

        return bytes_to_frames(runtime, pos);
}

static int camelot_pcm_new(struct snd_soc_component *component,
                           struct snd_soc_pcm_runtime *rtd)
{
        struct snd_pcm *pcm = rtd->pcm;

        /* dont use SNDRV_DMA_TYPE_DEV, since it will oops the SH kernel
         * in MMAP mode (i.e. aplay -M)
         */
        snd_pcm_set_managed_buffer_all(pcm,
                SNDRV_DMA_TYPE_CONTINUOUS,
                NULL,
                DMABRG_PREALLOC_BUFFER, DMABRG_PREALLOC_BUFFER_MAX);

        return 0;
}

static const struct snd_soc_component_driver sh7760_soc_component = {
        .open           = camelot_pcm_open,
        .close          = camelot_pcm_close,
        .hw_params      = camelot_hw_params,
        .prepare        = camelot_prepare,
        .trigger        = camelot_trigger,
        .pointer        = camelot_pos,
        .pcm_construct  = camelot_pcm_new,
};

static int sh7760_soc_platform_probe(struct platform_device *pdev)
{
        return devm_snd_soc_register_component(&pdev->dev, &sh7760_soc_component,
                                               NULL, 0);
}

static struct platform_driver sh7760_pcm_driver = {
        .driver = {
                        .name = "sh7760-pcm-audio",
        },

        .probe = sh7760_soc_platform_probe,
};

module_platform_driver(sh7760_pcm_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("SH7760 Audio DMA (DMABRG) driver");
MODULE_AUTHOR("Manuel Lauss <mano@roarinelk.homelinux.net>");