// SPDX-License-Identifier: GPL-2.0-only

  /*
   * SPI driver for Nvidia's Tegra20/Tegra30 SLINK Controller.
   *
   * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.

   */
  
  #include <linux/clk.h>
  #include <linux/completion.h>
  #include <linux/delay.h>
  #include <linux/dmaengine.h>
  #include <linux/dma-mapping.h>
  #include <linux/dmapool.h>
  #include <linux/err.h>

  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/kthread.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/pm_runtime.h>
  #include <linux/of.h>
  #include <linux/of_device.h>

  #include <linux/reset.h>

  #include <linux/spi/spi.h>

  
  #define SLINK_COMMAND			0x000
  #define SLINK_BIT_LENGTH(x)		(((x) & 0x1f) << 0)
  #define SLINK_WORD_SIZE(x)		(((x) & 0x1f) << 5)
  #define SLINK_BOTH_EN			(1 << 10)
  #define SLINK_CS_SW			(1 << 11)
  #define SLINK_CS_VALUE			(1 << 12)
  #define SLINK_CS_POLARITY		(1 << 13)
  #define SLINK_IDLE_SDA_DRIVE_LOW	(0 << 16)
  #define SLINK_IDLE_SDA_DRIVE_HIGH	(1 << 16)
  #define SLINK_IDLE_SDA_PULL_LOW		(2 << 16)
  #define SLINK_IDLE_SDA_PULL_HIGH	(3 << 16)
  #define SLINK_IDLE_SDA_MASK		(3 << 16)
  #define SLINK_CS_POLARITY1		(1 << 20)
  #define SLINK_CK_SDA			(1 << 21)
  #define SLINK_CS_POLARITY2		(1 << 22)
  #define SLINK_CS_POLARITY3		(1 << 23)
  #define SLINK_IDLE_SCLK_DRIVE_LOW	(0 << 24)
  #define SLINK_IDLE_SCLK_DRIVE_HIGH	(1 << 24)
  #define SLINK_IDLE_SCLK_PULL_LOW	(2 << 24)
  #define SLINK_IDLE_SCLK_PULL_HIGH	(3 << 24)
  #define SLINK_IDLE_SCLK_MASK		(3 << 24)
  #define SLINK_M_S			(1 << 28)
  #define SLINK_WAIT			(1 << 29)
  #define SLINK_GO			(1 << 30)
  #define SLINK_ENB			(1 << 31)
  
  #define SLINK_MODES			(SLINK_IDLE_SCLK_MASK | SLINK_CK_SDA)
  
  #define SLINK_COMMAND2			0x004
  #define SLINK_LSBFE			(1 << 0)
  #define SLINK_SSOE			(1 << 1)
  #define SLINK_SPIE			(1 << 4)
  #define SLINK_BIDIROE			(1 << 6)
  #define SLINK_MODFEN			(1 << 7)
  #define SLINK_INT_SIZE(x)		(((x) & 0x1f) << 8)
  #define SLINK_CS_ACTIVE_BETWEEN		(1 << 17)
  #define SLINK_SS_EN_CS(x)		(((x) & 0x3) << 18)
  #define SLINK_SS_SETUP(x)		(((x) & 0x3) << 20)
  #define SLINK_FIFO_REFILLS_0		(0 << 22)
  #define SLINK_FIFO_REFILLS_1		(1 << 22)
  #define SLINK_FIFO_REFILLS_2		(2 << 22)
  #define SLINK_FIFO_REFILLS_3		(3 << 22)
  #define SLINK_FIFO_REFILLS_MASK		(3 << 22)
  #define SLINK_WAIT_PACK_INT(x)		(((x) & 0x7) << 26)
  #define SLINK_SPC0			(1 << 29)
  #define SLINK_TXEN			(1 << 30)
  #define SLINK_RXEN			(1 << 31)
  
  #define SLINK_STATUS			0x008
  #define SLINK_COUNT(val)		(((val) >> 0) & 0x1f)
  #define SLINK_WORD(val)			(((val) >> 5) & 0x1f)
  #define SLINK_BLK_CNT(val)		(((val) >> 0) & 0xffff)
  #define SLINK_MODF			(1 << 16)
  #define SLINK_RX_UNF			(1 << 18)
  #define SLINK_TX_OVF			(1 << 19)
  #define SLINK_TX_FULL			(1 << 20)
  #define SLINK_TX_EMPTY			(1 << 21)
  #define SLINK_RX_FULL			(1 << 22)
  #define SLINK_RX_EMPTY			(1 << 23)
  #define SLINK_TX_UNF			(1 << 24)
  #define SLINK_RX_OVF			(1 << 25)
  #define SLINK_TX_FLUSH			(1 << 26)
  #define SLINK_RX_FLUSH			(1 << 27)
  #define SLINK_SCLK			(1 << 28)
  #define SLINK_ERR			(1 << 29)
  #define SLINK_RDY			(1 << 30)
  #define SLINK_BSY			(1 << 31)
  #define SLINK_FIFO_ERROR		(SLINK_TX_OVF | SLINK_RX_UNF |	\
  					SLINK_TX_UNF | SLINK_RX_OVF)
  
  #define SLINK_FIFO_EMPTY		(SLINK_TX_EMPTY | SLINK_RX_EMPTY)
  
  #define SLINK_MAS_DATA			0x010
  #define SLINK_SLAVE_DATA		0x014
  
  #define SLINK_DMA_CTL			0x018
  #define SLINK_DMA_BLOCK_SIZE(x)		(((x) & 0xffff) << 0)
  #define SLINK_TX_TRIG_1			(0 << 16)
  #define SLINK_TX_TRIG_4			(1 << 16)
  #define SLINK_TX_TRIG_8			(2 << 16)
  #define SLINK_TX_TRIG_16		(3 << 16)
  #define SLINK_TX_TRIG_MASK		(3 << 16)
  #define SLINK_RX_TRIG_1			(0 << 18)
  #define SLINK_RX_TRIG_4			(1 << 18)
  #define SLINK_RX_TRIG_8			(2 << 18)
  #define SLINK_RX_TRIG_16		(3 << 18)
  #define SLINK_RX_TRIG_MASK		(3 << 18)
  #define SLINK_PACKED			(1 << 20)
  #define SLINK_PACK_SIZE_4		(0 << 21)
  #define SLINK_PACK_SIZE_8		(1 << 21)
  #define SLINK_PACK_SIZE_16		(2 << 21)
  #define SLINK_PACK_SIZE_32		(3 << 21)
  #define SLINK_PACK_SIZE_MASK		(3 << 21)
  #define SLINK_IE_TXC			(1 << 26)
  #define SLINK_IE_RXC			(1 << 27)
  #define SLINK_DMA_EN			(1 << 31)
  
  #define SLINK_STATUS2			0x01c
  #define SLINK_TX_FIFO_EMPTY_COUNT(val)	(((val) & 0x3f) >> 0)
  #define SLINK_RX_FIFO_FULL_COUNT(val)	(((val) & 0x3f0000) >> 16)
  #define SLINK_SS_HOLD_TIME(val)		(((val) & 0xF) << 6)
  
  #define SLINK_TX_FIFO			0x100
  #define SLINK_RX_FIFO			0x180
  
  #define DATA_DIR_TX			(1 << 0)
  #define DATA_DIR_RX			(1 << 1)
  
  #define SLINK_DMA_TIMEOUT		(msecs_to_jiffies(1000))
  
  #define DEFAULT_SPI_DMA_BUF_LEN		(16*1024)
  #define TX_FIFO_EMPTY_COUNT_MAX		SLINK_TX_FIFO_EMPTY_COUNT(0x20)
  #define RX_FIFO_FULL_COUNT_ZERO		SLINK_RX_FIFO_FULL_COUNT(0)
  
  #define SLINK_STATUS2_RESET \
  	(TX_FIFO_EMPTY_COUNT_MAX | RX_FIFO_FULL_COUNT_ZERO << 16)
  
  #define MAX_CHIP_SELECT			4
  #define SLINK_FIFO_DEPTH		32
  
  struct tegra_slink_chip_data {
  	bool cs_hold_time;
  };
  
  struct tegra_slink_data {
  	struct device				*dev;
  	struct spi_master			*master;
  	const struct tegra_slink_chip_data	*chip_data;
  	spinlock_t				lock;
  
  	struct clk				*clk;

  	struct reset_control			*rst;

  	void __iomem				*base;
  	phys_addr_t				phys;
  	unsigned				irq;

  	u32					cur_speed;
  
  	struct spi_device			*cur_spi;
  	unsigned				cur_pos;
  	unsigned				cur_len;
  	unsigned				words_per_32bit;
  	unsigned				bytes_per_word;
  	unsigned				curr_dma_words;
  	unsigned				cur_direction;
  
  	unsigned				cur_rx_pos;
  	unsigned				cur_tx_pos;
  
  	unsigned				dma_buf_size;
  	unsigned				max_buf_size;
  	bool					is_curr_dma_xfer;

  
  	struct completion			rx_dma_complete;
  	struct completion			tx_dma_complete;
  
  	u32					tx_status;
  	u32					rx_status;
  	u32					status_reg;
  	bool					is_packed;

  	u32					packed_size;

  
  	u32					command_reg;
  	u32					command2_reg;
  	u32					dma_control_reg;
  	u32					def_command_reg;
  	u32					def_command2_reg;
  
  	struct completion			xfer_completion;
  	struct spi_transfer			*curr_xfer;
  	struct dma_chan				*rx_dma_chan;
  	u32					*rx_dma_buf;
  	dma_addr_t				rx_dma_phys;
  	struct dma_async_tx_descriptor		*rx_dma_desc;
  
  	struct dma_chan				*tx_dma_chan;
  	u32					*tx_dma_buf;
  	dma_addr_t				tx_dma_phys;
  	struct dma_async_tx_descriptor		*tx_dma_desc;
  };
  
  static int tegra_slink_runtime_suspend(struct device *dev);
  static int tegra_slink_runtime_resume(struct device *dev);

  static inline u32 tegra_slink_readl(struct tegra_slink_data *tspi,

  		unsigned long reg)
  {
  	return readl(tspi->base + reg);
  }
  
  static inline void tegra_slink_writel(struct tegra_slink_data *tspi,

  		u32 val, unsigned long reg)

  {
  	writel(val, tspi->base + reg);
  
  	/* Read back register to make sure that register writes completed */
  	if (reg != SLINK_TX_FIFO)
  		readl(tspi->base + SLINK_MAS_DATA);
  }
  
  static void tegra_slink_clear_status(struct tegra_slink_data *tspi)
  {

  	u32 val_write;

  	tegra_slink_readl(tspi, SLINK_STATUS);

  
  	/* Write 1 to clear status register */
  	val_write = SLINK_RDY | SLINK_FIFO_ERROR;
  	tegra_slink_writel(tspi, val_write, SLINK_STATUS);
  }

  static u32 tegra_slink_get_packed_size(struct tegra_slink_data *tspi,

  				  struct spi_transfer *t)
  {

  	switch (tspi->bytes_per_word) {
  	case 0:

  		return SLINK_PACK_SIZE_4;

  	case 1:

  		return SLINK_PACK_SIZE_8;

  	case 2:

  		return SLINK_PACK_SIZE_16;

  	case 4:

  		return SLINK_PACK_SIZE_32;

  	default:

  		return 0;

  	}

  }
  
  static unsigned tegra_slink_calculate_curr_xfer_param(
  	struct spi_device *spi, struct tegra_slink_data *tspi,
  	struct spi_transfer *t)
  {
  	unsigned remain_len = t->len - tspi->cur_pos;
  	unsigned max_word;

  	unsigned bits_per_word;

  	unsigned max_len;
  	unsigned total_fifo_words;

  	bits_per_word = t->bits_per_word;

  	tspi->bytes_per_word = DIV_ROUND_UP(bits_per_word, 8);

  
  	if (bits_per_word == 8 || bits_per_word == 16) {

  		tspi->is_packed = true;

  		tspi->words_per_32bit = 32/bits_per_word;
  	} else {

  		tspi->is_packed = false;

  		tspi->words_per_32bit = 1;
  	}
  	tspi->packed_size = tegra_slink_get_packed_size(tspi, t);
  
  	if (tspi->is_packed) {
  		max_len = min(remain_len, tspi->max_buf_size);
  		tspi->curr_dma_words = max_len/tspi->bytes_per_word;
  		total_fifo_words = max_len/4;
  	} else {
  		max_word = (remain_len - 1) / tspi->bytes_per_word + 1;
  		max_word = min(max_word, tspi->max_buf_size/4);
  		tspi->curr_dma_words = max_word;
  		total_fifo_words = max_word;
  	}
  	return total_fifo_words;
  }
  
  static unsigned tegra_slink_fill_tx_fifo_from_client_txbuf(
  	struct tegra_slink_data *tspi, struct spi_transfer *t)
  {
  	unsigned nbytes;
  	unsigned tx_empty_count;

  	u32 fifo_status;

  	unsigned max_n_32bit;
  	unsigned i, count;

  	unsigned int written_words;
  	unsigned fifo_words_left;
  	u8 *tx_buf = (u8 *)t->tx_buf + tspi->cur_tx_pos;
  
  	fifo_status = tegra_slink_readl(tspi, SLINK_STATUS2);
  	tx_empty_count = SLINK_TX_FIFO_EMPTY_COUNT(fifo_status);
  
  	if (tspi->is_packed) {
  		fifo_words_left = tx_empty_count * tspi->words_per_32bit;
  		written_words = min(fifo_words_left, tspi->curr_dma_words);
  		nbytes = written_words * tspi->bytes_per_word;
  		max_n_32bit = DIV_ROUND_UP(nbytes, 4);
  		for (count = 0; count < max_n_32bit; count++) {

  			u32 x = 0;

  			for (i = 0; (i < 4) && nbytes; i++, nbytes--)

  				x |= (u32)(*tx_buf++) << (i * 8);

  			tegra_slink_writel(tspi, x, SLINK_TX_FIFO);
  		}
  	} else {
  		max_n_32bit = min(tspi->curr_dma_words,  tx_empty_count);
  		written_words = max_n_32bit;
  		nbytes = written_words * tspi->bytes_per_word;
  		for (count = 0; count < max_n_32bit; count++) {

  			u32 x = 0;

  			for (i = 0; nbytes && (i < tspi->bytes_per_word);
  							i++, nbytes--)

  				x |= (u32)(*tx_buf++) << (i * 8);

  			tegra_slink_writel(tspi, x, SLINK_TX_FIFO);
  		}
  	}
  	tspi->cur_tx_pos += written_words * tspi->bytes_per_word;
  	return written_words;
  }
  
  static unsigned int tegra_slink_read_rx_fifo_to_client_rxbuf(
  		struct tegra_slink_data *tspi, struct spi_transfer *t)
  {
  	unsigned rx_full_count;

  	u32 fifo_status;

  	unsigned i, count;

  	unsigned int read_words = 0;
  	unsigned len;
  	u8 *rx_buf = (u8 *)t->rx_buf + tspi->cur_rx_pos;
  
  	fifo_status = tegra_slink_readl(tspi, SLINK_STATUS2);
  	rx_full_count = SLINK_RX_FIFO_FULL_COUNT(fifo_status);
  	if (tspi->is_packed) {
  		len = tspi->curr_dma_words * tspi->bytes_per_word;
  		for (count = 0; count < rx_full_count; count++) {

  			u32 x = tegra_slink_readl(tspi, SLINK_RX_FIFO);

  			for (i = 0; len && (i < 4); i++, len--)
  				*rx_buf++ = (x >> i*8) & 0xFF;
  		}
  		tspi->cur_rx_pos += tspi->curr_dma_words * tspi->bytes_per_word;
  		read_words += tspi->curr_dma_words;
  	} else {

  		for (count = 0; count < rx_full_count; count++) {

  			u32 x = tegra_slink_readl(tspi, SLINK_RX_FIFO);

  			for (i = 0; (i < tspi->bytes_per_word); i++)
  				*rx_buf++ = (x >> (i*8)) & 0xFF;
  		}
  		tspi->cur_rx_pos += rx_full_count * tspi->bytes_per_word;
  		read_words += rx_full_count;
  	}
  	return read_words;
  }
  
  static void tegra_slink_copy_client_txbuf_to_spi_txbuf(
  		struct tegra_slink_data *tspi, struct spi_transfer *t)
  {

  	/* Make the dma buffer to read by cpu */
  	dma_sync_single_for_cpu(tspi->dev, tspi->tx_dma_phys,
  				tspi->dma_buf_size, DMA_TO_DEVICE);
  
  	if (tspi->is_packed) {

  		unsigned len = tspi->curr_dma_words * tspi->bytes_per_word;

  		memcpy(tspi->tx_dma_buf, t->tx_buf + tspi->cur_pos, len);
  	} else {
  		unsigned int i;
  		unsigned int count;
  		u8 *tx_buf = (u8 *)t->tx_buf + tspi->cur_tx_pos;
  		unsigned consume = tspi->curr_dma_words * tspi->bytes_per_word;

  
  		for (count = 0; count < tspi->curr_dma_words; count++) {

  			u32 x = 0;

  			for (i = 0; consume && (i < tspi->bytes_per_word);
  							i++, consume--)

  				x |= (u32)(*tx_buf++) << (i * 8);

  			tspi->tx_dma_buf[count] = x;
  		}
  	}
  	tspi->cur_tx_pos += tspi->curr_dma_words * tspi->bytes_per_word;
  
  	/* Make the dma buffer to read by dma */
  	dma_sync_single_for_device(tspi->dev, tspi->tx_dma_phys,
  				tspi->dma_buf_size, DMA_TO_DEVICE);
  }
  
  static void tegra_slink_copy_spi_rxbuf_to_client_rxbuf(
  		struct tegra_slink_data *tspi, struct spi_transfer *t)
  {
  	unsigned len;
  
  	/* Make the dma buffer to read by cpu */
  	dma_sync_single_for_cpu(tspi->dev, tspi->rx_dma_phys,
  		tspi->dma_buf_size, DMA_FROM_DEVICE);
  
  	if (tspi->is_packed) {
  		len = tspi->curr_dma_words * tspi->bytes_per_word;
  		memcpy(t->rx_buf + tspi->cur_rx_pos, tspi->rx_dma_buf, len);
  	} else {
  		unsigned int i;
  		unsigned int count;
  		unsigned char *rx_buf = t->rx_buf + tspi->cur_rx_pos;

  		u32 rx_mask = ((u32)1 << t->bits_per_word) - 1;

  		for (count = 0; count < tspi->curr_dma_words; count++) {

  			u32 x = tspi->rx_dma_buf[count] & rx_mask;

  			for (i = 0; (i < tspi->bytes_per_word); i++)
  				*rx_buf++ = (x >> (i*8)) & 0xFF;
  		}
  	}
  	tspi->cur_rx_pos += tspi->curr_dma_words * tspi->bytes_per_word;
  
  	/* Make the dma buffer to read by dma */
  	dma_sync_single_for_device(tspi->dev, tspi->rx_dma_phys,
  		tspi->dma_buf_size, DMA_FROM_DEVICE);
  }
  
  static void tegra_slink_dma_complete(void *args)
  {
  	struct completion *dma_complete = args;
  
  	complete(dma_complete);
  }
  
  static int tegra_slink_start_tx_dma(struct tegra_slink_data *tspi, int len)
  {

  	reinit_completion(&tspi->tx_dma_complete);

  	tspi->tx_dma_desc = dmaengine_prep_slave_single(tspi->tx_dma_chan,
  				tspi->tx_dma_phys, len, DMA_MEM_TO_DEV,

  				DMA_PREP_INTERRUPT |  DMA_CTRL_ACK);

  	if (!tspi->tx_dma_desc) {
  		dev_err(tspi->dev, "Not able to get desc for Tx
  ");
  		return -EIO;
  	}
  
  	tspi->tx_dma_desc->callback = tegra_slink_dma_complete;
  	tspi->tx_dma_desc->callback_param = &tspi->tx_dma_complete;
  
  	dmaengine_submit(tspi->tx_dma_desc);
  	dma_async_issue_pending(tspi->tx_dma_chan);
  	return 0;
  }
  
  static int tegra_slink_start_rx_dma(struct tegra_slink_data *tspi, int len)
  {

  	reinit_completion(&tspi->rx_dma_complete);

  	tspi->rx_dma_desc = dmaengine_prep_slave_single(tspi->rx_dma_chan,
  				tspi->rx_dma_phys, len, DMA_DEV_TO_MEM,

  				DMA_PREP_INTERRUPT |  DMA_CTRL_ACK);

  	if (!tspi->rx_dma_desc) {
  		dev_err(tspi->dev, "Not able to get desc for Rx
  ");
  		return -EIO;
  	}
  
  	tspi->rx_dma_desc->callback = tegra_slink_dma_complete;
  	tspi->rx_dma_desc->callback_param = &tspi->rx_dma_complete;
  
  	dmaengine_submit(tspi->rx_dma_desc);
  	dma_async_issue_pending(tspi->rx_dma_chan);
  	return 0;
  }
  
  static int tegra_slink_start_dma_based_transfer(
  		struct tegra_slink_data *tspi, struct spi_transfer *t)
  {

  	u32 val;

  	unsigned int len;
  	int ret = 0;

  	u32 status;

  
  	/* Make sure that Rx and Tx fifo are empty */
  	status = tegra_slink_readl(tspi, SLINK_STATUS);
  	if ((status & SLINK_FIFO_EMPTY) != SLINK_FIFO_EMPTY) {

  		dev_err(tspi->dev, "Rx/Tx fifo are not empty status 0x%08x
  ",
  			(unsigned)status);

  		return -EIO;
  	}
  
  	val = SLINK_DMA_BLOCK_SIZE(tspi->curr_dma_words - 1);
  	val |= tspi->packed_size;
  	if (tspi->is_packed)
  		len = DIV_ROUND_UP(tspi->curr_dma_words * tspi->bytes_per_word,
  					4) * 4;
  	else
  		len = tspi->curr_dma_words * 4;
  
  	/* Set attention level based on length of transfer */
  	if (len & 0xF)
  		val |= SLINK_TX_TRIG_1 | SLINK_RX_TRIG_1;
  	else if (((len) >> 4) & 0x1)
  		val |= SLINK_TX_TRIG_4 | SLINK_RX_TRIG_4;
  	else
  		val |= SLINK_TX_TRIG_8 | SLINK_RX_TRIG_8;
  
  	if (tspi->cur_direction & DATA_DIR_TX)
  		val |= SLINK_IE_TXC;
  
  	if (tspi->cur_direction & DATA_DIR_RX)
  		val |= SLINK_IE_RXC;
  
  	tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  	tspi->dma_control_reg = val;
  
  	if (tspi->cur_direction & DATA_DIR_TX) {
  		tegra_slink_copy_client_txbuf_to_spi_txbuf(tspi, t);
  		wmb();
  		ret = tegra_slink_start_tx_dma(tspi, len);
  		if (ret < 0) {
  			dev_err(tspi->dev,
  				"Starting tx dma failed, err %d
  ", ret);
  			return ret;
  		}
  
  		/* Wait for tx fifo to be fill before starting slink */

  		status = tegra_slink_readl(tspi, SLINK_STATUS);
  		while (!(status & SLINK_TX_FULL))
  			status = tegra_slink_readl(tspi, SLINK_STATUS);

  	}
  
  	if (tspi->cur_direction & DATA_DIR_RX) {
  		/* Make the dma buffer to read by dma */
  		dma_sync_single_for_device(tspi->dev, tspi->rx_dma_phys,
  				tspi->dma_buf_size, DMA_FROM_DEVICE);
  
  		ret = tegra_slink_start_rx_dma(tspi, len);
  		if (ret < 0) {
  			dev_err(tspi->dev,
  				"Starting rx dma failed, err %d
  ", ret);
  			if (tspi->cur_direction & DATA_DIR_TX)
  				dmaengine_terminate_all(tspi->tx_dma_chan);
  			return ret;
  		}
  	}
  	tspi->is_curr_dma_xfer = true;
  	if (tspi->is_packed) {
  		val |= SLINK_PACKED;
  		tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  		/* HW need small delay after settign Packed mode */
  		udelay(1);
  	}
  	tspi->dma_control_reg = val;
  
  	val |= SLINK_DMA_EN;
  	tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  	return ret;
  }
  
  static int tegra_slink_start_cpu_based_transfer(
  		struct tegra_slink_data *tspi, struct spi_transfer *t)
  {

  	u32 val;

  	unsigned cur_words;
  
  	val = tspi->packed_size;
  	if (tspi->cur_direction & DATA_DIR_TX)
  		val |= SLINK_IE_TXC;
  
  	if (tspi->cur_direction & DATA_DIR_RX)
  		val |= SLINK_IE_RXC;
  
  	tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  	tspi->dma_control_reg = val;
  
  	if (tspi->cur_direction & DATA_DIR_TX)
  		cur_words = tegra_slink_fill_tx_fifo_from_client_txbuf(tspi, t);
  	else
  		cur_words = tspi->curr_dma_words;
  	val |= SLINK_DMA_BLOCK_SIZE(cur_words - 1);
  	tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  	tspi->dma_control_reg = val;
  
  	tspi->is_curr_dma_xfer = false;
  	if (tspi->is_packed) {
  		val |= SLINK_PACKED;
  		tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  		udelay(1);
  		wmb();
  	}
  	tspi->dma_control_reg = val;
  	val |= SLINK_DMA_EN;
  	tegra_slink_writel(tspi, val, SLINK_DMA_CTL);
  	return 0;
  }
  
  static int tegra_slink_init_dma_param(struct tegra_slink_data *tspi,
  			bool dma_to_memory)
  {
  	struct dma_chan *dma_chan;
  	u32 *dma_buf;
  	dma_addr_t dma_phys;
  	int ret;
  	struct dma_slave_config dma_sconfig;

  	dma_chan = dma_request_chan(tspi->dev, dma_to_memory ? "rx" : "tx");

  	if (IS_ERR(dma_chan))
  		return dev_err_probe(tspi->dev, PTR_ERR(dma_chan),
  				     "Dma channel is not available
  ");

  
  	dma_buf = dma_alloc_coherent(tspi->dev, tspi->dma_buf_size,
  				&dma_phys, GFP_KERNEL);
  	if (!dma_buf) {
  		dev_err(tspi->dev, " Not able to allocate the dma buffer
  ");
  		dma_release_channel(dma_chan);
  		return -ENOMEM;
  	}

  	if (dma_to_memory) {
  		dma_sconfig.src_addr = tspi->phys + SLINK_RX_FIFO;
  		dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
  		dma_sconfig.src_maxburst = 0;
  	} else {
  		dma_sconfig.dst_addr = tspi->phys + SLINK_TX_FIFO;
  		dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
  		dma_sconfig.dst_maxburst = 0;
  	}
  
  	ret = dmaengine_slave_config(dma_chan, &dma_sconfig);
  	if (ret)
  		goto scrub;
  	if (dma_to_memory) {
  		tspi->rx_dma_chan = dma_chan;
  		tspi->rx_dma_buf = dma_buf;
  		tspi->rx_dma_phys = dma_phys;
  	} else {
  		tspi->tx_dma_chan = dma_chan;
  		tspi->tx_dma_buf = dma_buf;
  		tspi->tx_dma_phys = dma_phys;
  	}
  	return 0;
  
  scrub:
  	dma_free_coherent(tspi->dev, tspi->dma_buf_size, dma_buf, dma_phys);
  	dma_release_channel(dma_chan);
  	return ret;
  }
  
  static void tegra_slink_deinit_dma_param(struct tegra_slink_data *tspi,
  	bool dma_to_memory)
  {
  	u32 *dma_buf;
  	dma_addr_t dma_phys;
  	struct dma_chan *dma_chan;
  
  	if (dma_to_memory) {
  		dma_buf = tspi->rx_dma_buf;
  		dma_chan = tspi->rx_dma_chan;
  		dma_phys = tspi->rx_dma_phys;
  		tspi->rx_dma_chan = NULL;
  		tspi->rx_dma_buf = NULL;
  	} else {
  		dma_buf = tspi->tx_dma_buf;
  		dma_chan = tspi->tx_dma_chan;
  		dma_phys = tspi->tx_dma_phys;
  		tspi->tx_dma_buf = NULL;
  		tspi->tx_dma_chan = NULL;
  	}
  	if (!dma_chan)
  		return;
  
  	dma_free_coherent(tspi->dev, tspi->dma_buf_size, dma_buf, dma_phys);
  	dma_release_channel(dma_chan);
  }
  
  static int tegra_slink_start_transfer_one(struct spi_device *spi,

  		struct spi_transfer *t)

  {
  	struct tegra_slink_data *tspi = spi_master_get_devdata(spi->master);
  	u32 speed;
  	u8 bits_per_word;
  	unsigned total_fifo_words;
  	int ret;

  	u32 command;
  	u32 command2;

  	bits_per_word = t->bits_per_word;

  	speed = t->speed_hz;

  	if (speed != tspi->cur_speed) {
  		clk_set_rate(tspi->clk, speed * 4);
  		tspi->cur_speed = speed;
  	}
  
  	tspi->cur_spi = spi;
  	tspi->cur_pos = 0;
  	tspi->cur_rx_pos = 0;
  	tspi->cur_tx_pos = 0;
  	tspi->curr_xfer = t;
  	total_fifo_words = tegra_slink_calculate_curr_xfer_param(spi, tspi, t);

  	command = tspi->command_reg;
  	command &= ~SLINK_BIT_LENGTH(~0);
  	command |= SLINK_BIT_LENGTH(bits_per_word - 1);

  	command2 = tspi->command2_reg;
  	command2 &= ~(SLINK_RXEN | SLINK_TXEN);

  	tspi->cur_direction = 0;
  	if (t->rx_buf) {
  		command2 |= SLINK_RXEN;
  		tspi->cur_direction |= DATA_DIR_RX;
  	}
  	if (t->tx_buf) {
  		command2 |= SLINK_TXEN;
  		tspi->cur_direction |= DATA_DIR_TX;
  	}

  
  	/*
  	 * Writing to the command2 register bevore the command register prevents
  	 * a spike in chip_select line 0. This selects the chip_select line
  	 * before changing the chip_select value.
  	 */

  	tegra_slink_writel(tspi, command2, SLINK_COMMAND2);
  	tspi->command2_reg = command2;

  	tegra_slink_writel(tspi, command, SLINK_COMMAND);
  	tspi->command_reg = command;

  	if (total_fifo_words > SLINK_FIFO_DEPTH)
  		ret = tegra_slink_start_dma_based_transfer(tspi, t);
  	else
  		ret = tegra_slink_start_cpu_based_transfer(tspi, t);
  	return ret;
  }
  
  static int tegra_slink_setup(struct spi_device *spi)
  {

  	static const u32 cs_pol_bit[MAX_CHIP_SELECT] = {

  			SLINK_CS_POLARITY,
  			SLINK_CS_POLARITY1,
  			SLINK_CS_POLARITY2,
  			SLINK_CS_POLARITY3,
  	};

  	struct tegra_slink_data *tspi = spi_master_get_devdata(spi->master);
  	u32 val;
  	unsigned long flags;
  	int ret;

  	dev_dbg(&spi->dev, "setup %d bpw, %scpol, %scpha, %dHz
  ",
  		spi->bits_per_word,
  		spi->mode & SPI_CPOL ? "" : "~",
  		spi->mode & SPI_CPHA ? "" : "~",
  		spi->max_speed_hz);

  	ret = pm_runtime_get_sync(tspi->dev);
  	if (ret < 0) {

  		pm_runtime_put_noidle(tspi->dev);

  		dev_err(tspi->dev, "pm runtime failed, e = %d
  ", ret);
  		return ret;
  	}
  
  	spin_lock_irqsave(&tspi->lock, flags);
  	val = tspi->def_command_reg;
  	if (spi->mode & SPI_CS_HIGH)
  		val |= cs_pol_bit[spi->chip_select];
  	else
  		val &= ~cs_pol_bit[spi->chip_select];
  	tspi->def_command_reg = val;
  	tegra_slink_writel(tspi, tspi->def_command_reg, SLINK_COMMAND);
  	spin_unlock_irqrestore(&tspi->lock, flags);
  
  	pm_runtime_put(tspi->dev);
  	return 0;
  }

  static int tegra_slink_prepare_message(struct spi_master *master,
  				       struct spi_message *msg)

  {

  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);

  	struct spi_device *spi = msg->spi;

  	tegra_slink_clear_status(tspi);

  	tspi->command_reg = tspi->def_command_reg;
  	tspi->command_reg |= SLINK_CS_SW | SLINK_CS_VALUE;

  	tspi->command2_reg = tspi->def_command2_reg;
  	tspi->command2_reg |= SLINK_SS_EN_CS(spi->chip_select);
  
  	tspi->command_reg &= ~SLINK_MODES;
  	if (spi->mode & SPI_CPHA)
  		tspi->command_reg |= SLINK_CK_SDA;
  
  	if (spi->mode & SPI_CPOL)
  		tspi->command_reg |= SLINK_IDLE_SCLK_DRIVE_HIGH;
  	else
  		tspi->command_reg |= SLINK_IDLE_SCLK_DRIVE_LOW;

  	return 0;
  }

  static int tegra_slink_transfer_one(struct spi_master *master,
  				    struct spi_device *spi,
  				    struct spi_transfer *xfer)
  {
  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);
  	int ret;

  	reinit_completion(&tspi->xfer_completion);

  	ret = tegra_slink_start_transfer_one(spi, xfer);

  	if (ret < 0) {
  		dev_err(tspi->dev,
  			"spi can not start transfer, err %d
  ", ret);
  		return ret;

  	}

  	ret = wait_for_completion_timeout(&tspi->xfer_completion,
  					  SLINK_DMA_TIMEOUT);
  	if (WARN_ON(ret == 0)) {
  		dev_err(tspi->dev,

  			"spi transfer timeout, err %d
  ", ret);

  		return -EIO;
  	}
  
  	if (tspi->tx_status)
  		return tspi->tx_status;
  	if (tspi->rx_status)
  		return tspi->rx_status;
  
  	return 0;
  }
  
  static int tegra_slink_unprepare_message(struct spi_master *master,
  					 struct spi_message *msg)
  {
  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);

  	tegra_slink_writel(tspi, tspi->def_command_reg, SLINK_COMMAND);
  	tegra_slink_writel(tspi, tspi->def_command2_reg, SLINK_COMMAND2);

  
  	return 0;

  }
  
  static irqreturn_t handle_cpu_based_xfer(struct tegra_slink_data *tspi)
  {
  	struct spi_transfer *t = tspi->curr_xfer;
  	unsigned long flags;
  
  	spin_lock_irqsave(&tspi->lock, flags);
  	if (tspi->tx_status ||  tspi->rx_status ||
  				(tspi->status_reg & SLINK_BSY)) {
  		dev_err(tspi->dev,
  			"CpuXfer ERROR bit set 0x%x
  ", tspi->status_reg);
  		dev_err(tspi->dev,
  			"CpuXfer 0x%08x:0x%08x:0x%08x
  ", tspi->command_reg,
  				tspi->command2_reg, tspi->dma_control_reg);

  		reset_control_assert(tspi->rst);

  		udelay(2);

  		reset_control_deassert(tspi->rst);

  		complete(&tspi->xfer_completion);
  		goto exit;
  	}
  
  	if (tspi->cur_direction & DATA_DIR_RX)
  		tegra_slink_read_rx_fifo_to_client_rxbuf(tspi, t);
  
  	if (tspi->cur_direction & DATA_DIR_TX)
  		tspi->cur_pos = tspi->cur_tx_pos;
  	else
  		tspi->cur_pos = tspi->cur_rx_pos;
  
  	if (tspi->cur_pos == t->len) {
  		complete(&tspi->xfer_completion);
  		goto exit;
  	}
  
  	tegra_slink_calculate_curr_xfer_param(tspi->cur_spi, tspi, t);
  	tegra_slink_start_cpu_based_transfer(tspi, t);
  exit:
  	spin_unlock_irqrestore(&tspi->lock, flags);
  	return IRQ_HANDLED;
  }
  
  static irqreturn_t handle_dma_based_xfer(struct tegra_slink_data *tspi)
  {
  	struct spi_transfer *t = tspi->curr_xfer;
  	long wait_status;
  	int err = 0;
  	unsigned total_fifo_words;
  	unsigned long flags;
  
  	/* Abort dmas if any error */
  	if (tspi->cur_direction & DATA_DIR_TX) {
  		if (tspi->tx_status) {
  			dmaengine_terminate_all(tspi->tx_dma_chan);
  			err += 1;
  		} else {
  			wait_status = wait_for_completion_interruptible_timeout(
  				&tspi->tx_dma_complete, SLINK_DMA_TIMEOUT);
  			if (wait_status <= 0) {
  				dmaengine_terminate_all(tspi->tx_dma_chan);
  				dev_err(tspi->dev, "TxDma Xfer failed
  ");
  				err += 1;
  			}
  		}
  	}
  
  	if (tspi->cur_direction & DATA_DIR_RX) {
  		if (tspi->rx_status) {
  			dmaengine_terminate_all(tspi->rx_dma_chan);
  			err += 2;
  		} else {
  			wait_status = wait_for_completion_interruptible_timeout(
  				&tspi->rx_dma_complete, SLINK_DMA_TIMEOUT);
  			if (wait_status <= 0) {
  				dmaengine_terminate_all(tspi->rx_dma_chan);
  				dev_err(tspi->dev, "RxDma Xfer failed
  ");
  				err += 2;
  			}
  		}
  	}
  
  	spin_lock_irqsave(&tspi->lock, flags);
  	if (err) {
  		dev_err(tspi->dev,
  			"DmaXfer: ERROR bit set 0x%x
  ", tspi->status_reg);
  		dev_err(tspi->dev,
  			"DmaXfer 0x%08x:0x%08x:0x%08x
  ", tspi->command_reg,
  				tspi->command2_reg, tspi->dma_control_reg);

  		reset_control_assert(tspi->rst);

  		udelay(2);

  		reset_control_assert(tspi->rst);

  		complete(&tspi->xfer_completion);
  		spin_unlock_irqrestore(&tspi->lock, flags);
  		return IRQ_HANDLED;
  	}
  
  	if (tspi->cur_direction & DATA_DIR_RX)
  		tegra_slink_copy_spi_rxbuf_to_client_rxbuf(tspi, t);
  
  	if (tspi->cur_direction & DATA_DIR_TX)
  		tspi->cur_pos = tspi->cur_tx_pos;
  	else
  		tspi->cur_pos = tspi->cur_rx_pos;
  
  	if (tspi->cur_pos == t->len) {
  		complete(&tspi->xfer_completion);
  		goto exit;
  	}
  
  	/* Continue transfer in current message */
  	total_fifo_words = tegra_slink_calculate_curr_xfer_param(tspi->cur_spi,
  							tspi, t);
  	if (total_fifo_words > SLINK_FIFO_DEPTH)
  		err = tegra_slink_start_dma_based_transfer(tspi, t);
  	else
  		err = tegra_slink_start_cpu_based_transfer(tspi, t);
  
  exit:
  	spin_unlock_irqrestore(&tspi->lock, flags);
  	return IRQ_HANDLED;
  }
  
  static irqreturn_t tegra_slink_isr_thread(int irq, void *context_data)
  {
  	struct tegra_slink_data *tspi = context_data;
  
  	if (!tspi->is_curr_dma_xfer)
  		return handle_cpu_based_xfer(tspi);
  	return handle_dma_based_xfer(tspi);
  }
  
  static irqreturn_t tegra_slink_isr(int irq, void *context_data)
  {
  	struct tegra_slink_data *tspi = context_data;
  
  	tspi->status_reg = tegra_slink_readl(tspi, SLINK_STATUS);
  	if (tspi->cur_direction & DATA_DIR_TX)
  		tspi->tx_status = tspi->status_reg &
  					(SLINK_TX_OVF | SLINK_TX_UNF);
  
  	if (tspi->cur_direction & DATA_DIR_RX)
  		tspi->rx_status = tspi->status_reg &
  					(SLINK_RX_OVF | SLINK_RX_UNF);
  	tegra_slink_clear_status(tspi);
  
  	return IRQ_WAKE_THREAD;
  }

  static const struct tegra_slink_chip_data tegra30_spi_cdata = {

  	.cs_hold_time = true,
  };

  static const struct tegra_slink_chip_data tegra20_spi_cdata = {

  	.cs_hold_time = false,
  };

  static const struct of_device_id tegra_slink_of_match[] = {

  	{ .compatible = "nvidia,tegra30-slink", .data = &tegra30_spi_cdata, },

  	{ .compatible = "nvidia,tegra20-slink", .data = &tegra20_spi_cdata, },

  	{}
  };
  MODULE_DEVICE_TABLE(of, tegra_slink_of_match);

  static int tegra_slink_probe(struct platform_device *pdev)

  {
  	struct spi_master	*master;
  	struct tegra_slink_data	*tspi;
  	struct resource		*r;

  	int ret, spi_irq;
  	const struct tegra_slink_chip_data *cdata = NULL;
  	const struct of_device_id *match;

  	match = of_match_device(tegra_slink_of_match, &pdev->dev);

  	if (!match) {
  		dev_err(&pdev->dev, "Error: No device match found
  ");
  		return -ENODEV;
  	}
  	cdata = match->data;

  
  	master = spi_alloc_master(&pdev->dev, sizeof(*tspi));
  	if (!master) {
  		dev_err(&pdev->dev, "master allocation failed
  ");
  		return -ENOMEM;
  	}
  
  	/* the spi->mode bits understood by this driver: */
  	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
  	master->setup = tegra_slink_setup;

  	master->prepare_message = tegra_slink_prepare_message;
  	master->transfer_one = tegra_slink_transfer_one;
  	master->unprepare_message = tegra_slink_unprepare_message;

  	master->auto_runtime_pm = true;

  	master->num_chipselect = MAX_CHIP_SELECT;

  	platform_set_drvdata(pdev, master);

  	tspi = spi_master_get_devdata(master);
  	tspi->master = master;

  	tspi->dev = &pdev->dev;
  	tspi->chip_data = cdata;
  	spin_lock_init(&tspi->lock);

  	if (of_property_read_u32(tspi->dev->of_node, "spi-max-frequency",
  				 &master->max_speed_hz))
  		master->max_speed_hz = 25000000; /* 25MHz */

  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!r) {
  		dev_err(&pdev->dev, "No IO memory resource
  ");
  		ret = -ENODEV;
  		goto exit_free_master;
  	}
  	tspi->phys = r->start;

  	tspi->base = devm_ioremap_resource(&pdev->dev, r);
  	if (IS_ERR(tspi->base)) {
  		ret = PTR_ERR(tspi->base);

  		goto exit_free_master;
  	}

  	/* disabled clock may cause interrupt storm upon request */
  	tspi->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(tspi->clk)) {
  		ret = PTR_ERR(tspi->clk);
  		dev_err(&pdev->dev, "Can not get clock %d
  ", ret);
  		goto exit_free_master;
  	}
  	ret = clk_prepare(tspi->clk);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "Clock prepare failed %d
  ", ret);
  		goto exit_free_master;
  	}
  	ret = clk_enable(tspi->clk);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "Clock enable failed %d
  ", ret);

  		goto exit_clk_unprepare;

  	}

  	spi_irq = platform_get_irq(pdev, 0);
  	tspi->irq = spi_irq;
  	ret = request_threaded_irq(tspi->irq, tegra_slink_isr,
  			tegra_slink_isr_thread, IRQF_ONESHOT,
  			dev_name(&pdev->dev), tspi);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "Failed to register ISR for IRQ %d
  ",
  					tspi->irq);

  		goto exit_clk_disable;

  	}

  	tspi->rst = devm_reset_control_get_exclusive(&pdev->dev, "spi");

  	if (IS_ERR(tspi->rst)) {
  		dev_err(&pdev->dev, "can not get reset
  ");
  		ret = PTR_ERR(tspi->rst);
  		goto exit_free_irq;
  	}

  	tspi->max_buf_size = SLINK_FIFO_DEPTH << 2;
  	tspi->dma_buf_size = DEFAULT_SPI_DMA_BUF_LEN;

  	ret = tegra_slink_init_dma_param(tspi, true);
  	if (ret < 0)
  		goto exit_free_irq;
  	ret = tegra_slink_init_dma_param(tspi, false);
  	if (ret < 0)
  		goto exit_rx_dma_free;
  	tspi->max_buf_size = tspi->dma_buf_size;
  	init_completion(&tspi->tx_dma_complete);
  	init_completion(&tspi->rx_dma_complete);

  
  	init_completion(&tspi->xfer_completion);
  
  	pm_runtime_enable(&pdev->dev);
  	if (!pm_runtime_enabled(&pdev->dev)) {
  		ret = tegra_slink_runtime_resume(&pdev->dev);
  		if (ret)
  			goto exit_pm_disable;
  	}
  
  	ret = pm_runtime_get_sync(&pdev->dev);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "pm runtime get failed, e = %d
  ", ret);

  		pm_runtime_put_noidle(&pdev->dev);

  		goto exit_pm_disable;
  	}
  	tspi->def_command_reg  = SLINK_M_S;
  	tspi->def_command2_reg = SLINK_CS_ACTIVE_BETWEEN;
  	tegra_slink_writel(tspi, tspi->def_command_reg, SLINK_COMMAND);
  	tegra_slink_writel(tspi, tspi->def_command2_reg, SLINK_COMMAND2);
  	pm_runtime_put(&pdev->dev);
  
  	master->dev.of_node = pdev->dev.of_node;

  	ret = devm_spi_register_master(&pdev->dev, master);

  	if (ret < 0) {
  		dev_err(&pdev->dev, "can not register to master err %d
  ", ret);
  		goto exit_pm_disable;
  	}
  	return ret;
  
  exit_pm_disable:
  	pm_runtime_disable(&pdev->dev);
  	if (!pm_runtime_status_suspended(&pdev->dev))
  		tegra_slink_runtime_suspend(&pdev->dev);
  	tegra_slink_deinit_dma_param(tspi, false);
  exit_rx_dma_free:
  	tegra_slink_deinit_dma_param(tspi, true);
  exit_free_irq:
  	free_irq(spi_irq, tspi);

  exit_clk_disable:
  	clk_disable(tspi->clk);

  exit_clk_unprepare:
  	clk_unprepare(tspi->clk);

  exit_free_master:
  	spi_master_put(master);
  	return ret;
  }

  static int tegra_slink_remove(struct platform_device *pdev)

  {

  	struct spi_master *master = platform_get_drvdata(pdev);

  	struct tegra_slink_data	*tspi = spi_master_get_devdata(master);
  
  	free_irq(tspi->irq, tspi);

  	clk_disable(tspi->clk);

  	clk_unprepare(tspi->clk);

  	if (tspi->tx_dma_chan)
  		tegra_slink_deinit_dma_param(tspi, false);
  
  	if (tspi->rx_dma_chan)
  		tegra_slink_deinit_dma_param(tspi, true);
  
  	pm_runtime_disable(&pdev->dev);
  	if (!pm_runtime_status_suspended(&pdev->dev))
  		tegra_slink_runtime_suspend(&pdev->dev);
  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int tegra_slink_suspend(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  
  	return spi_master_suspend(master);
  }
  
  static int tegra_slink_resume(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);
  	int ret;
  
  	ret = pm_runtime_get_sync(dev);
  	if (ret < 0) {

  		pm_runtime_put_noidle(dev);

  		dev_err(dev, "pm runtime failed, e = %d
  ", ret);
  		return ret;
  	}
  	tegra_slink_writel(tspi, tspi->command_reg, SLINK_COMMAND);
  	tegra_slink_writel(tspi, tspi->command2_reg, SLINK_COMMAND2);
  	pm_runtime_put(dev);
  
  	return spi_master_resume(master);
  }
  #endif
  
  static int tegra_slink_runtime_suspend(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);
  
  	/* Flush all write which are in PPSB queue by reading back */
  	tegra_slink_readl(tspi, SLINK_MAS_DATA);
  
  	clk_disable_unprepare(tspi->clk);
  	return 0;
  }
  
  static int tegra_slink_runtime_resume(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_slink_data *tspi = spi_master_get_devdata(master);
  	int ret;
  
  	ret = clk_prepare_enable(tspi->clk);
  	if (ret < 0) {
  		dev_err(tspi->dev, "clk_prepare failed: %d
  ", ret);
  		return ret;
  	}
  	return 0;
  }
  
  static const struct dev_pm_ops slink_pm_ops = {
  	SET_RUNTIME_PM_OPS(tegra_slink_runtime_suspend,
  		tegra_slink_runtime_resume, NULL)
  	SET_SYSTEM_SLEEP_PM_OPS(tegra_slink_suspend, tegra_slink_resume)
  };
  static struct platform_driver tegra_slink_driver = {
  	.driver = {
  		.name		= "spi-tegra-slink",

  		.pm		= &slink_pm_ops,

  		.of_match_table	= tegra_slink_of_match,

  	},
  	.probe =	tegra_slink_probe,

  	.remove =	tegra_slink_remove,

  };
  module_platform_driver(tegra_slink_driver);
  
  MODULE_ALIAS("platform:spi-tegra-slink");
  MODULE_DESCRIPTION("NVIDIA Tegra20/Tegra30 SLINK Controller Driver");
  MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
  MODULE_LICENSE("GPL v2");