/*
   * Sequencer Serial Port (SSP) based SPI master driver
   *
   * Copyright (C) 2010 Texas Instruments Inc
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/kernel.h>
  #include <linux/err.h>
  #include <linux/completion.h>
  #include <linux/delay.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/spi/spi.h>
  #include <linux/mfd/ti_ssp.h>
  
  #define MODE_BITS	(SPI_CPHA | SPI_CPOL | SPI_CS_HIGH)
  
  struct ti_ssp_spi {
  	struct spi_master		*master;
  	struct device			*dev;
  	spinlock_t			lock;
  	struct list_head		msg_queue;
  	struct completion		complete;
  	bool				shutdown;
  	struct workqueue_struct		*workqueue;
  	struct work_struct		work;
  	u8				mode, bpw;
  	int				cs_active;
  	u32				pc_en, pc_dis, pc_wr, pc_rd;
  	void				(*select)(int cs);
  };
  
  static u32 ti_ssp_spi_rx(struct ti_ssp_spi *hw)
  {
  	u32 ret;
  
  	ti_ssp_run(hw->dev, hw->pc_rd, 0, &ret);
  	return ret;
  }
  
  static void ti_ssp_spi_tx(struct ti_ssp_spi *hw, u32 data)
  {
  	ti_ssp_run(hw->dev, hw->pc_wr, data << (32 - hw->bpw), NULL);
  }
  
  static int ti_ssp_spi_txrx(struct ti_ssp_spi *hw, struct spi_message *msg,
  		       struct spi_transfer *t)
  {
  	int count;
  
  	if (hw->bpw <= 8) {
  		u8		*rx = t->rx_buf;
  		const u8	*tx = t->tx_buf;
  
  		for (count = 0; count < t->len; count += 1) {
  			if (t->tx_buf)
  				ti_ssp_spi_tx(hw, *tx++);
  			if (t->rx_buf)
  				*rx++ = ti_ssp_spi_rx(hw);
  		}
  	} else if (hw->bpw <= 16) {
  		u16		*rx = t->rx_buf;
  		const u16	*tx = t->tx_buf;
  
  		for (count = 0; count < t->len; count += 2) {
  			if (t->tx_buf)
  				ti_ssp_spi_tx(hw, *tx++);
  			if (t->rx_buf)
  				*rx++ = ti_ssp_spi_rx(hw);
  		}
  	} else {
  		u32		*rx = t->rx_buf;
  		const u32	*tx = t->tx_buf;
  
  		for (count = 0; count < t->len; count += 4) {
  			if (t->tx_buf)
  				ti_ssp_spi_tx(hw, *tx++);
  			if (t->rx_buf)
  				*rx++ = ti_ssp_spi_rx(hw);
  		}
  	}
  
  	msg->actual_length += count; /* bytes transferred */
  
  	dev_dbg(&msg->spi->dev, "xfer %s%s, %d bytes, %d bpw, count %d%s
  ",
  		t->tx_buf ? "tx" : "", t->rx_buf ? "rx" : "", t->len,
  		hw->bpw, count, (count < t->len) ? " (under)" : "");
  
  	return (count < t->len) ? -EIO : 0; /* left over data */
  }
  
  static void ti_ssp_spi_chip_select(struct ti_ssp_spi *hw, int cs_active)
  {
  	cs_active = !!cs_active;
  	if (cs_active == hw->cs_active)
  		return;
  	ti_ssp_run(hw->dev, cs_active ? hw->pc_en : hw->pc_dis, 0, NULL);
  	hw->cs_active = cs_active;
  }
  
  #define __SHIFT_OUT(bits)	(SSP_OPCODE_SHIFT | SSP_OUT_MODE | \
  				 cs_en | clk | SSP_COUNT((bits) * 2 - 1))
  #define __SHIFT_IN(bits)	(SSP_OPCODE_SHIFT | SSP_IN_MODE  | \
  				 cs_en | clk | SSP_COUNT((bits) * 2 - 1))
  
  static int ti_ssp_spi_setup_transfer(struct ti_ssp_spi *hw, u8 bpw, u8 mode)
  {
  	int error, idx = 0;
  	u32 seqram[16];
  	u32 cs_en, cs_dis, clk;
  	u32 topbits, botbits;
  
  	mode &= MODE_BITS;
  	if (mode == hw->mode && bpw == hw->bpw)
  		return 0;
  
  	cs_en  = (mode & SPI_CS_HIGH) ? SSP_CS_HIGH : SSP_CS_LOW;
  	cs_dis = (mode & SPI_CS_HIGH) ? SSP_CS_LOW  : SSP_CS_HIGH;
  	clk    = (mode & SPI_CPOL)    ? SSP_CLK_HIGH : SSP_CLK_LOW;
  
  	/* Construct instructions */
  
  	/* Disable Chip Select */
  	hw->pc_dis = idx;
  	seqram[idx++] = SSP_OPCODE_DIRECT | SSP_OUT_MODE | cs_dis | clk;
  	seqram[idx++] = SSP_OPCODE_STOP   | SSP_OUT_MODE | cs_dis | clk;
  
  	/* Enable Chip Select */
  	hw->pc_en = idx;
  	seqram[idx++] = SSP_OPCODE_DIRECT | SSP_OUT_MODE | cs_en | clk;
  	seqram[idx++] = SSP_OPCODE_STOP   | SSP_OUT_MODE | cs_en | clk;
  
  	/* Reads and writes need to be split for bpw > 16 */
  	topbits = (bpw > 16) ? 16 : bpw;
  	botbits = bpw - topbits;
  
  	/* Write */
  	hw->pc_wr = idx;
  	seqram[idx++] = __SHIFT_OUT(topbits) | SSP_ADDR_REG;
  	if (botbits)
  		seqram[idx++] = __SHIFT_OUT(botbits)  | SSP_DATA_REG;
  	seqram[idx++] = SSP_OPCODE_STOP | SSP_OUT_MODE | cs_en | clk;
  
  	/* Read */
  	hw->pc_rd = idx;
  	if (botbits)
  		seqram[idx++] = __SHIFT_IN(botbits) | SSP_ADDR_REG;
  	seqram[idx++] = __SHIFT_IN(topbits) | SSP_DATA_REG;
  	seqram[idx++] = SSP_OPCODE_STOP | SSP_OUT_MODE | cs_en | clk;
  
  	error = ti_ssp_load(hw->dev, 0, seqram, idx);
  	if (error < 0)
  		return error;
  
  	error = ti_ssp_set_mode(hw->dev, ((mode & SPI_CPHA) ?
  					  0 : SSP_EARLY_DIN));
  	if (error < 0)
  		return error;
  
  	hw->bpw = bpw;
  	hw->mode = mode;
  
  	return error;
  }
  
  static void ti_ssp_spi_work(struct work_struct *work)
  {
  	struct ti_ssp_spi *hw = container_of(work, struct ti_ssp_spi, work);
  
  	spin_lock(&hw->lock);
  
  	 while (!list_empty(&hw->msg_queue)) {
  		struct spi_message	*m;
  		struct spi_device	*spi;
  		struct spi_transfer	*t = NULL;
  		int			status = 0;
  
  		m = container_of(hw->msg_queue.next, struct spi_message,
  				 queue);
  
  		list_del_init(&m->queue);
  
  		spin_unlock(&hw->lock);
  
  		spi = m->spi;
  
  		if (hw->select)
  			hw->select(spi->chip_select);
  
  		list_for_each_entry(t, &m->transfers, transfer_list) {
  			int bpw = spi->bits_per_word;
  			int xfer_status;
  
  			if (t->bits_per_word)
  				bpw = t->bits_per_word;
  
  			if (ti_ssp_spi_setup_transfer(hw, bpw, spi->mode) < 0)
  				break;
  
  			ti_ssp_spi_chip_select(hw, 1);
  
  			xfer_status = ti_ssp_spi_txrx(hw, m, t);
  			if (xfer_status < 0)
  				status = xfer_status;
  
  			if (t->delay_usecs)
  				udelay(t->delay_usecs);
  
  			if (t->cs_change)
  				ti_ssp_spi_chip_select(hw, 0);
  		}
  
  		ti_ssp_spi_chip_select(hw, 0);
  		m->status = status;
  		m->complete(m->context);
  
  		spin_lock(&hw->lock);
  	}
  
  	if (hw->shutdown)
  		complete(&hw->complete);
  
  	spin_unlock(&hw->lock);
  }
  
  static int ti_ssp_spi_transfer(struct spi_device *spi, struct spi_message *m)
  {
  	struct ti_ssp_spi	*hw;
  	struct spi_transfer	*t;
  	int			error = 0;
  
  	m->actual_length = 0;
  	m->status = -EINPROGRESS;
  
  	hw = spi_master_get_devdata(spi->master);
  
  	if (list_empty(&m->transfers) || !m->complete)
  		return -EINVAL;
  
  	list_for_each_entry(t, &m->transfers, transfer_list) {
  		if (t->len && !(t->rx_buf || t->tx_buf)) {
  			dev_err(&spi->dev, "invalid xfer, no buffer
  ");
  			return -EINVAL;
  		}
  
  		if (t->len && t->rx_buf && t->tx_buf) {
  			dev_err(&spi->dev, "invalid xfer, full duplex
  ");
  			return -EINVAL;
  		}
  	}
  
  	spin_lock(&hw->lock);
  	if (hw->shutdown) {
  		error = -ESHUTDOWN;
  		goto error_unlock;
  	}
  	list_add_tail(&m->queue, &hw->msg_queue);
  	queue_work(hw->workqueue, &hw->work);
  error_unlock:
  	spin_unlock(&hw->lock);
  	return error;
  }
  
  static int ti_ssp_spi_probe(struct platform_device *pdev)
  {
  	const struct ti_ssp_spi_data *pdata;
  	struct ti_ssp_spi *hw;
  	struct spi_master *master;
  	struct device *dev = &pdev->dev;
  	int error = 0;
  
  	pdata = dev_get_platdata(dev);
  	if (!pdata) {
  		dev_err(dev, "platform data not found
  ");
  		return -EINVAL;
  	}
  
  	master = spi_alloc_master(dev, sizeof(struct ti_ssp_spi));
  	if (!master) {
  		dev_err(dev, "cannot allocate SPI master
  ");
  		return -ENOMEM;
  	}
  
  	hw = spi_master_get_devdata(master);
  	platform_set_drvdata(pdev, hw);
  
  	hw->master = master;
  	hw->dev = dev;
  	hw->select = pdata->select;
  
  	spin_lock_init(&hw->lock);
  	init_completion(&hw->complete);
  	INIT_LIST_HEAD(&hw->msg_queue);
  	INIT_WORK(&hw->work, ti_ssp_spi_work);
  
  	hw->workqueue = create_singlethread_workqueue(dev_name(dev));
  	if (!hw->workqueue) {
  		error = -ENOMEM;
  		dev_err(dev, "work queue creation failed
  ");
  		goto error_wq;
  	}
  
  	error = ti_ssp_set_iosel(hw->dev, pdata->iosel);
  	if (error < 0) {
  		dev_err(dev, "io setup failed
  ");
  		goto error_iosel;
  	}
  
  	master->bus_num		= pdev->id;
  	master->num_chipselect	= pdata->num_cs;
  	master->mode_bits	= MODE_BITS;
  	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
  	master->flags		= SPI_MASTER_HALF_DUPLEX;
  	master->transfer	= ti_ssp_spi_transfer;
  
  	error = spi_register_master(master);
  	if (error) {
  		dev_err(dev, "master registration failed
  ");
  		goto error_reg;
  	}
  
  	return 0;
  
  error_reg:
  error_iosel:
  	destroy_workqueue(hw->workqueue);
  error_wq:
  	spi_master_put(master);
  	return error;
  }
  
  static int ti_ssp_spi_remove(struct platform_device *pdev)
  {
  	struct ti_ssp_spi *hw = platform_get_drvdata(pdev);
  	int error;
  
  	hw->shutdown = 1;
  	while (!list_empty(&hw->msg_queue)) {
  		error = wait_for_completion_interruptible(&hw->complete);
  		if (error < 0) {
  			hw->shutdown = 0;
  			return error;
  		}
  	}
  	destroy_workqueue(hw->workqueue);
  	spi_unregister_master(hw->master);
  
  	return 0;
  }
  
  static struct platform_driver ti_ssp_spi_driver = {
  	.probe		= ti_ssp_spi_probe,
  	.remove		= ti_ssp_spi_remove,
  	.driver		= {
  		.name	= "ti-ssp-spi",
  		.owner	= THIS_MODULE,
  	},
  };
  module_platform_driver(ti_ssp_spi_driver);
  
  MODULE_DESCRIPTION("SSP SPI Master");
  MODULE_AUTHOR("Cyril Chemparathy");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:ti-ssp-spi");