/*
 * rt5677-spi.c  --  RT5677 ALSA SoC audio codec driver
 *
 * Copyright 2013 Realtek Semiconductor Corp.
 * Author: Oder Chiou <oder_chiou@realtek.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/input.h>
#include <linux/spi/spi.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/slab.h>
#include <linux/gpio.h>
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/regulator/consumer.h>
#include <linux/pm_qos.h>
#include <linux/sysfs.h>
#include <linux/clk.h>
#include <linux/firmware.h>

#include "rt5677-spi.h"

#define RT5677_SPI_BURST_LEN    240
#define RT5677_SPI_HEADER       5
#define RT5677_SPI_FREQ         6000000

/* The AddressPhase and DataPhase of SPI commands are MSB first on the wire.
 * DataPhase word size of 16-bit commands is 2 bytes.
 * DataPhase word size of 32-bit commands is 4 bytes.
 * DataPhase word size of burst commands is 8 bytes.
 * The DSP CPU is little-endian.
 */
#define RT5677_SPI_WRITE_BURST  0x5
#define RT5677_SPI_READ_BURST   0x4
#define RT5677_SPI_WRITE_32     0x3
#define RT5677_SPI_READ_32      0x2
#define RT5677_SPI_WRITE_16     0x1
#define RT5677_SPI_READ_16      0x0

static struct spi_device *g_spi;
static DEFINE_MUTEX(spi_mutex);

/* Select a suitable transfer command for the next transfer to ensure
 * the transfer address is always naturally aligned while minimizing
 * the total number of transfers required.
 *
 * 3 transfer commands are available:
 * RT5677_SPI_READ/WRITE_16:    Transfer 2 bytes
 * RT5677_SPI_READ/WRITE_32:    Transfer 4 bytes
 * RT5677_SPI_READ/WRITE_BURST: Transfer any multiples of 8 bytes
 *
 * For example, reading 260 bytes at 0x60030002 uses the following commands:
 * 0x60030002 RT5677_SPI_READ_16        2 bytes
 * 0x60030004 RT5677_SPI_READ_32        4 bytes
 * 0x60030008 RT5677_SPI_READ_BURST     240 bytes
 * 0x600300F8 RT5677_SPI_READ_BURST     8 bytes
 * 0x60030100 RT5677_SPI_READ_32        4 bytes
 * 0x60030104 RT5677_SPI_READ_16        2 bytes
 *
 * Input:
 * @read: true for read commands; false for write commands
 * @align: alignment of the next transfer address
 * @remain: number of bytes remaining to transfer
 *
 * Output:
 * @len: number of bytes to transfer with the selected command
 * Returns the selected command
 */
static u8 rt5677_spi_select_cmd(bool read, u32 align, u32 remain, u32 *len)
{
        u8 cmd;

        if (align == 2 || align == 6 || remain == 2) {
                cmd = RT5677_SPI_READ_16;
                *len = 2;
        } else if (align == 4 || remain <= 6) {
                cmd = RT5677_SPI_READ_32;
                *len = 4;
        } else {
                cmd = RT5677_SPI_READ_BURST;
                *len = min_t(u32, remain & ~7, RT5677_SPI_BURST_LEN);
        }
        return read ? cmd : cmd + 1;
}

/* Copy dstlen bytes from src to dst, while reversing byte order for each word.
 * If srclen < dstlen, zeros are padded.
 */
static void rt5677_spi_reverse(u8 *dst, u32 dstlen, const u8 *src, u32 srclen)
{
        u32 w, i, si;
        u32 word_size = min_t(u32, dstlen, 8);

        for (w = 0; w < dstlen; w += word_size) {
                for (i = 0; i < word_size; i++) {
                        si = w + word_size - i - 1;
                        dst[w + i] = si < srclen ? src[si] : 0;
                }
        }
}

/* Read DSP address space using SPI. addr and len have to be 2-byte aligned. */
int rt5677_spi_read(u32 addr, void *rxbuf, size_t len)
{
        u32 offset;
        int status = 0;
        struct spi_transfer t[2];
        struct spi_message m;
        /* +4 bytes is for the DummyPhase following the AddressPhase */
        u8 header[RT5677_SPI_HEADER + 4];
        u8 body[RT5677_SPI_BURST_LEN];
        u8 spi_cmd;
        u8 *cb = rxbuf;

        if (!g_spi)
                return -ENODEV;

        if ((addr & 1) || (len & 1)) {
                dev_err(&g_spi->dev, "Bad read align 0x%x(%zu)\n", addr, len);
                return -EACCES;
        }

        memset(t, 0, sizeof(t));
        t[0].tx_buf = header;
        t[0].len = sizeof(header);
        t[0].speed_hz = RT5677_SPI_FREQ;
        t[1].rx_buf = body;
        t[1].speed_hz = RT5677_SPI_FREQ;
        spi_message_init_with_transfers(&m, t, ARRAY_SIZE(t));

        for (offset = 0; offset < len; offset += t[1].len) {
                spi_cmd = rt5677_spi_select_cmd(true, (addr + offset) & 7,
                                len - offset, &t[1].len);

                /* Construct SPI message header */
                header[0] = spi_cmd;
                header[1] = ((addr + offset) & 0xff000000) >> 24;
                header[2] = ((addr + offset) & 0x00ff0000) >> 16;
                header[3] = ((addr + offset) & 0x0000ff00) >> 8;
                header[4] = ((addr + offset) & 0x000000ff) >> 0;

                mutex_lock(&spi_mutex);
                status |= spi_sync(g_spi, &m);
                mutex_unlock(&spi_mutex);

                /* Copy data back to caller buffer */
                rt5677_spi_reverse(cb + offset, t[1].len, body, t[1].len);
        }
        return status;
}
EXPORT_SYMBOL_GPL(rt5677_spi_read);

/* Write DSP address space using SPI. addr has to be 2-byte aligned.
 * If len is not 2-byte aligned, an extra byte of zero is written at the end
 * as padding.
 */
int rt5677_spi_write(u32 addr, const void *txbuf, size_t len)
{
        u32 offset, len_with_pad = len;
        int status = 0;
        struct spi_transfer t;
        struct spi_message m;
        /* +1 byte is for the DummyPhase following the DataPhase */
        u8 buf[RT5677_SPI_HEADER + RT5677_SPI_BURST_LEN + 1];
        u8 *body = buf + RT5677_SPI_HEADER;
        u8 spi_cmd;
        const u8 *cb = txbuf;

        if (!g_spi)
                return -ENODEV;

        if (addr & 1) {
                dev_err(&g_spi->dev, "Bad write align 0x%x(%zu)\n", addr, len);
                return -EACCES;
        }

        if (len & 1)
                len_with_pad = len + 1;

        memset(&t, 0, sizeof(t));
        t.tx_buf = buf;
        t.speed_hz = RT5677_SPI_FREQ;
        spi_message_init_with_transfers(&m, &t, 1);

        for (offset = 0; offset < len_with_pad;) {
                spi_cmd = rt5677_spi_select_cmd(false, (addr + offset) & 7,
                                len_with_pad - offset, &t.len);

                /* Construct SPI message header */
                buf[0] = spi_cmd;
                buf[1] = ((addr + offset) & 0xff000000) >> 24;
                buf[2] = ((addr + offset) & 0x00ff0000) >> 16;
                buf[3] = ((addr + offset) & 0x0000ff00) >> 8;
                buf[4] = ((addr + offset) & 0x000000ff) >> 0;

                /* Fetch data from caller buffer */
                rt5677_spi_reverse(body, t.len, cb + offset, len - offset);
                offset += t.len;
                t.len += RT5677_SPI_HEADER + 1;

                mutex_lock(&spi_mutex);
                status |= spi_sync(g_spi, &m);
                mutex_unlock(&spi_mutex);
        }
        return status;
}
EXPORT_SYMBOL_GPL(rt5677_spi_write);

int rt5677_spi_write_firmware(u32 addr, const struct firmware *fw)
{
        return rt5677_spi_write(addr, fw->data, fw->size);
}
EXPORT_SYMBOL_GPL(rt5677_spi_write_firmware);

static int rt5677_spi_probe(struct spi_device *spi)
{
        g_spi = spi;
        return 0;
}

static struct spi_driver rt5677_spi_driver = {
        .driver = {
                .name = "rt5677",
                .owner = THIS_MODULE,
        },
        .probe = rt5677_spi_probe,
};
module_spi_driver(rt5677_spi_driver);

MODULE_DESCRIPTION("ASoC RT5677 SPI driver");
MODULE_AUTHOR("Oder Chiou <oder_chiou@realtek.com>");
MODULE_LICENSE("GPL v2");