/*
   * Analog Devices AD-FMCOMMS1-EBZ board I2C-SPI bridge driver
   *
   * Copyright 2012 Analog Devices Inc.
   * Author: Lars-Peter Clausen <lars@metafoo.de>
   *
   * Licensed under the GPL-2 or later.
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/delay.h>
  #include <linux/i2c.h>
  #include <linux/spi/spi.h>
  #include <asm/unaligned.h>
  
  #define SPI_XCOMM_SETTINGS_LEN_OFFSET		10
  #define SPI_XCOMM_SETTINGS_3WIRE		BIT(6)
  #define SPI_XCOMM_SETTINGS_CS_HIGH		BIT(5)
  #define SPI_XCOMM_SETTINGS_SAMPLE_END		BIT(4)
  #define SPI_XCOMM_SETTINGS_CPHA			BIT(3)
  #define SPI_XCOMM_SETTINGS_CPOL			BIT(2)
  #define SPI_XCOMM_SETTINGS_CLOCK_DIV_MASK	0x3
  #define SPI_XCOMM_SETTINGS_CLOCK_DIV_64		0x2
  #define SPI_XCOMM_SETTINGS_CLOCK_DIV_16		0x1
  #define SPI_XCOMM_SETTINGS_CLOCK_DIV_4		0x0
  
  #define SPI_XCOMM_CMD_UPDATE_CONFIG	0x03
  #define SPI_XCOMM_CMD_WRITE		0x04
  
  #define SPI_XCOMM_CLOCK 48000000
  
  struct spi_xcomm {
  	struct i2c_client *i2c;
  
  	uint16_t settings;
  	uint16_t chipselect;
  
  	unsigned int current_speed;
  
  	uint8_t buf[63];
  };
  
  static int spi_xcomm_sync_config(struct spi_xcomm *spi_xcomm, unsigned int len)
  {
  	uint16_t settings;
  	uint8_t *buf = spi_xcomm->buf;
  
  	settings = spi_xcomm->settings;
  	settings |= len << SPI_XCOMM_SETTINGS_LEN_OFFSET;
  
  	buf[0] = SPI_XCOMM_CMD_UPDATE_CONFIG;
  	put_unaligned_be16(settings, &buf[1]);
  	put_unaligned_be16(spi_xcomm->chipselect, &buf[3]);
  
  	return i2c_master_send(spi_xcomm->i2c, buf, 5);
  }
  
  static void spi_xcomm_chipselect(struct spi_xcomm *spi_xcomm,
  	struct spi_device *spi, int is_active)
  {
  	unsigned long cs = spi->chip_select;
  	uint16_t chipselect = spi_xcomm->chipselect;
  
  	if (is_active)
  		chipselect |= BIT(cs);
  	else
  		chipselect &= ~BIT(cs);
  
  	spi_xcomm->chipselect = chipselect;
  }
  
  static int spi_xcomm_setup_transfer(struct spi_xcomm *spi_xcomm,
  	struct spi_device *spi, struct spi_transfer *t, unsigned int *settings)
  {
  	if (t->len > 62)
  		return -EINVAL;
  
  	if (t->speed_hz != spi_xcomm->current_speed) {
  		unsigned int divider;
  
  		divider = DIV_ROUND_UP(SPI_XCOMM_CLOCK, t->speed_hz);
  		if (divider >= 64)
  			*settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_64;
  		else if (divider >= 16)
  			*settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_16;
  		else
  			*settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_4;
  
  		spi_xcomm->current_speed = t->speed_hz;
  	}
  
  	if (spi->mode & SPI_CPOL)
  		*settings |= SPI_XCOMM_SETTINGS_CPOL;
  	else
  		*settings &= ~SPI_XCOMM_SETTINGS_CPOL;
  
  	if (spi->mode & SPI_CPHA)
  		*settings &= ~SPI_XCOMM_SETTINGS_CPHA;
  	else
  		*settings |= SPI_XCOMM_SETTINGS_CPHA;
  
  	if (spi->mode & SPI_3WIRE)
  		*settings |= SPI_XCOMM_SETTINGS_3WIRE;
  	else
  		*settings &= ~SPI_XCOMM_SETTINGS_3WIRE;
  
  	return 0;
  }
  
  static int spi_xcomm_txrx_bufs(struct spi_xcomm *spi_xcomm,
  	struct spi_device *spi, struct spi_transfer *t)
  {
  	int ret;
  
  	if (t->tx_buf) {
  		spi_xcomm->buf[0] = SPI_XCOMM_CMD_WRITE;
  		memcpy(spi_xcomm->buf + 1, t->tx_buf, t->len);
  
  		ret = i2c_master_send(spi_xcomm->i2c, spi_xcomm->buf, t->len + 1);
  		if (ret < 0)
  			return ret;
  		else if (ret != t->len + 1)
  			return -EIO;
  	} else if (t->rx_buf) {
  		ret = i2c_master_recv(spi_xcomm->i2c, t->rx_buf, t->len);
  		if (ret < 0)
  			return ret;
  		else if (ret != t->len)
  			return -EIO;
  	}
  
  	return t->len;
  }
  
  static int spi_xcomm_transfer_one(struct spi_master *master,
  	struct spi_message *msg)
  {
  	struct spi_xcomm *spi_xcomm = spi_master_get_devdata(master);
  	unsigned int settings = spi_xcomm->settings;
  	struct spi_device *spi = msg->spi;
  	unsigned cs_change = 0;
  	struct spi_transfer *t;
  	bool is_first = true;
  	int status = 0;
  	bool is_last;
  
  	spi_xcomm_chipselect(spi_xcomm, spi, true);
  
  	list_for_each_entry(t, &msg->transfers, transfer_list) {
  
  		if (!t->tx_buf && !t->rx_buf && t->len) {
  			status = -EINVAL;
  			break;
  		}
  
  		status = spi_xcomm_setup_transfer(spi_xcomm, spi, t, &settings);
  		if (status < 0)
  			break;
  
  		is_last = list_is_last(&t->transfer_list, &msg->transfers);
  		cs_change = t->cs_change;
  
  		if (cs_change ^ is_last)
  			settings |= BIT(5);
  		else
  			settings &= ~BIT(5);
  
  		if (t->rx_buf) {
  			spi_xcomm->settings = settings;
  			status = spi_xcomm_sync_config(spi_xcomm, t->len);
  			if (status < 0)
  				break;
  		} else if (settings != spi_xcomm->settings || is_first) {
  			spi_xcomm->settings = settings;
  			status = spi_xcomm_sync_config(spi_xcomm, 0);
  			if (status < 0)
  				break;
  		}
  
  		if (t->len) {
  			status = spi_xcomm_txrx_bufs(spi_xcomm, spi, t);
  
  			if (status < 0)
  				break;
  
  			if (status > 0)
  				msg->actual_length += status;
  		}
  		status = 0;
  
  		if (t->delay_usecs)
  			udelay(t->delay_usecs);
  
  		is_first = false;
  	}
  
  	if (status != 0 || !cs_change)
  		spi_xcomm_chipselect(spi_xcomm, spi, false);
  
  	msg->status = status;
  	spi_finalize_current_message(master);
  
  	return status;
  }
  
  static int spi_xcomm_probe(struct i2c_client *i2c,
  	const struct i2c_device_id *id)
  {
  	struct spi_xcomm *spi_xcomm;
  	struct spi_master *master;
  	int ret;
  
  	master = spi_alloc_master(&i2c->dev, sizeof(*spi_xcomm));
  	if (!master)
  		return -ENOMEM;
  
  	spi_xcomm = spi_master_get_devdata(master);
  	spi_xcomm->i2c = i2c;
  
  	master->num_chipselect = 16;
  	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_3WIRE;
  	master->bits_per_word_mask = SPI_BPW_MASK(8);
  	master->flags = SPI_MASTER_HALF_DUPLEX;
  	master->transfer_one_message = spi_xcomm_transfer_one;
  	master->dev.of_node = i2c->dev.of_node;
  	i2c_set_clientdata(i2c, master);
  
  	ret = devm_spi_register_master(&i2c->dev, master);
  	if (ret < 0)
  		spi_master_put(master);
  
  	return ret;
  }
  
  static const struct i2c_device_id spi_xcomm_ids[] = {
  	{ "spi-xcomm" },
  	{ },
  };
  MODULE_DEVICE_TABLE(i2c, spi_xcomm_ids);
  
  static struct i2c_driver spi_xcomm_driver = {
  	.driver = {
  		.name	= "spi-xcomm",
  	},
  	.id_table	= spi_xcomm_ids,
  	.probe		= spi_xcomm_probe,
  };
  module_i2c_driver(spi_xcomm_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
  MODULE_DESCRIPTION("Analog Devices AD-FMCOMMS1-EBZ board I2C-SPI bridge driver");