i2c-cadence.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * I2C bus driver for the Cadence I2C controller.
 *
 * Copyright (C) 2009 - 2014 Xilinx, Inc.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/pm_runtime.h>

/* Register offsets for the I2C device. */
#define CDNS_I2C_CR_OFFSET		0x00 /* Control Register, RW */
#define CDNS_I2C_SR_OFFSET		0x04 /* Status Register, RO */
#define CDNS_I2C_ADDR_OFFSET		0x08 /* I2C Address Register, RW */
#define CDNS_I2C_DATA_OFFSET		0x0C /* I2C Data Register, RW */
#define CDNS_I2C_ISR_OFFSET		0x10 /* IRQ Status Register, RW */
#define CDNS_I2C_XFER_SIZE_OFFSET	0x14 /* Transfer Size Register, RW */
#define CDNS_I2C_TIME_OUT_OFFSET	0x1C /* Time Out Register, RW */
#define CDNS_I2C_IMR_OFFSET		0x20 /* IRQ Mask Register, RO */
#define CDNS_I2C_IER_OFFSET		0x24 /* IRQ Enable Register, WO */
#define CDNS_I2C_IDR_OFFSET		0x28 /* IRQ Disable Register, WO */

/* Control Register Bit mask definitions */
#define CDNS_I2C_CR_HOLD		BIT(4) /* Hold Bus bit */
#define CDNS_I2C_CR_ACK_EN		BIT(3)
#define CDNS_I2C_CR_NEA			BIT(2)
#define CDNS_I2C_CR_MS			BIT(1)
/* Read or Write Master transfer 0 = Transmitter, 1 = Receiver */
#define CDNS_I2C_CR_RW			BIT(0)
/* 1 = Auto init FIFO to zeroes */
#define CDNS_I2C_CR_CLR_FIFO		BIT(6)
#define CDNS_I2C_CR_DIVA_SHIFT		14
#define CDNS_I2C_CR_DIVA_MASK		(3 << CDNS_I2C_CR_DIVA_SHIFT)
#define CDNS_I2C_CR_DIVB_SHIFT		8
#define CDNS_I2C_CR_DIVB_MASK		(0x3f << CDNS_I2C_CR_DIVB_SHIFT)

#define CDNS_I2C_CR_MASTER_EN_MASK	(CDNS_I2C_CR_NEA | \
					 CDNS_I2C_CR_ACK_EN | \
					 CDNS_I2C_CR_MS)

#define CDNS_I2C_CR_SLAVE_EN_MASK	~CDNS_I2C_CR_MASTER_EN_MASK

/* Status Register Bit mask definitions */
#define CDNS_I2C_SR_BA		BIT(8)
#define CDNS_I2C_SR_TXDV	BIT(6)
#define CDNS_I2C_SR_RXDV	BIT(5)
#define CDNS_I2C_SR_RXRW	BIT(3)

/*
 * I2C Address Register Bit mask definitions
 * Normal addressing mode uses [6:0] bits. Extended addressing mode uses [9:0]
 * bits. A write access to this register always initiates a transfer if the I2C
 * is in master mode.
 */
#define CDNS_I2C_ADDR_MASK	0x000003FF /* I2C Address Mask */

/*
 * I2C Interrupt Registers Bit mask definitions
 * All the four interrupt registers (Status/Mask/Enable/Disable) have the same
 * bit definitions.
 */
#define CDNS_I2C_IXR_ARB_LOST		BIT(9)
#define CDNS_I2C_IXR_RX_UNF		BIT(7)
#define CDNS_I2C_IXR_TX_OVF		BIT(6)
#define CDNS_I2C_IXR_RX_OVF		BIT(5)
#define CDNS_I2C_IXR_SLV_RDY		BIT(4)
#define CDNS_I2C_IXR_TO			BIT(3)
#define CDNS_I2C_IXR_NACK		BIT(2)
#define CDNS_I2C_IXR_DATA		BIT(1)
#define CDNS_I2C_IXR_COMP		BIT(0)

#define CDNS_I2C_IXR_ALL_INTR_MASK	(CDNS_I2C_IXR_ARB_LOST | \
					 CDNS_I2C_IXR_RX_UNF | \
					 CDNS_I2C_IXR_TX_OVF | \
					 CDNS_I2C_IXR_RX_OVF | \
					 CDNS_I2C_IXR_SLV_RDY | \
					 CDNS_I2C_IXR_TO | \
					 CDNS_I2C_IXR_NACK | \
					 CDNS_I2C_IXR_DATA | \
					 CDNS_I2C_IXR_COMP)

#define CDNS_I2C_IXR_ERR_INTR_MASK	(CDNS_I2C_IXR_ARB_LOST | \
					 CDNS_I2C_IXR_RX_UNF | \
					 CDNS_I2C_IXR_TX_OVF | \
					 CDNS_I2C_IXR_RX_OVF | \
					 CDNS_I2C_IXR_NACK)

#define CDNS_I2C_ENABLED_INTR_MASK	(CDNS_I2C_IXR_ARB_LOST | \
					 CDNS_I2C_IXR_RX_UNF | \
					 CDNS_I2C_IXR_TX_OVF | \
					 CDNS_I2C_IXR_RX_OVF | \
					 CDNS_I2C_IXR_NACK | \
					 CDNS_I2C_IXR_DATA | \
					 CDNS_I2C_IXR_COMP)

#define CDNS_I2C_IXR_SLAVE_INTR_MASK	(CDNS_I2C_IXR_RX_UNF | \
					 CDNS_I2C_IXR_TX_OVF | \
					 CDNS_I2C_IXR_RX_OVF | \
					 CDNS_I2C_IXR_TO | \
					 CDNS_I2C_IXR_NACK | \
					 CDNS_I2C_IXR_DATA | \
					 CDNS_I2C_IXR_COMP)

#define CDNS_I2C_TIMEOUT		msecs_to_jiffies(1000)
/* timeout for pm runtime autosuspend */
#define CNDS_I2C_PM_TIMEOUT		1000	/* ms */

#define CDNS_I2C_FIFO_DEPTH		16
/* FIFO depth at which the DATA interrupt occurs */
#define CDNS_I2C_DATA_INTR_DEPTH	(CDNS_I2C_FIFO_DEPTH - 2)
#define CDNS_I2C_MAX_TRANSFER_SIZE	255
/* Transfer size in multiples of data interrupt depth */
#define CDNS_I2C_TRANSFER_SIZE	(CDNS_I2C_MAX_TRANSFER_SIZE - 3)

#define DRIVER_NAME		"cdns-i2c"

#define CDNS_I2C_DIVA_MAX	4
#define CDNS_I2C_DIVB_MAX	64

#define CDNS_I2C_TIMEOUT_MAX	0xFF

#define CDNS_I2C_BROKEN_HOLD_BIT	BIT(0)

#define cdns_i2c_readreg(offset)       readl_relaxed(id->membase + offset)
#define cdns_i2c_writereg(val, offset) writel_relaxed(val, id->membase + offset)

#if IS_ENABLED(CONFIG_I2C_SLAVE)
/**
 * enum cdns_i2c_mode - I2C Controller current operating mode
 *
 * @CDNS_I2C_MODE_SLAVE:       I2C controller operating in slave mode
 * @CDNS_I2C_MODE_MASTER:      I2C Controller operating in master mode
 */
enum cdns_i2c_mode {
	CDNS_I2C_MODE_SLAVE,
	CDNS_I2C_MODE_MASTER,
};

/**
 * enum cdns_i2c_slave_mode - Slave state when I2C is operating in slave mode
 *
 * @CDNS_I2C_SLAVE_STATE_IDLE: I2C slave idle
 * @CDNS_I2C_SLAVE_STATE_SEND: I2C slave sending data to master
 * @CDNS_I2C_SLAVE_STATE_RECV: I2C slave receiving data from master
 */
enum cdns_i2c_slave_state {
	CDNS_I2C_SLAVE_STATE_IDLE,
	CDNS_I2C_SLAVE_STATE_SEND,
	CDNS_I2C_SLAVE_STATE_RECV,
};
#endif

/**
 * struct cdns_i2c - I2C device private data structure
 *
 * @dev:		Pointer to device structure
 * @membase:		Base address of the I2C device
 * @adap:		I2C adapter instance
 * @p_msg:		Message pointer
 * @err_status:		Error status in Interrupt Status Register
 * @xfer_done:		Transfer complete status
 * @p_send_buf:		Pointer to transmit buffer
 * @p_recv_buf:		Pointer to receive buffer
 * @send_count:		Number of bytes still expected to send
 * @recv_count:		Number of bytes still expected to receive
 * @curr_recv_count:	Number of bytes to be received in current transfer
 * @irq:		IRQ number
 * @input_clk:		Input clock to I2C controller
 * @i2c_clk:		Maximum I2C clock speed
 * @bus_hold_flag:	Flag used in repeated start for clearing HOLD bit
 * @clk:		Pointer to struct clk
 * @clk_rate_change_nb:	Notifier block for clock rate changes
 * @quirks:		flag for broken hold bit usage in r1p10
 * @ctrl_reg_diva_divb: value of fields DIV_A and DIV_B from CR register
 * @slave:		Registered slave instance.
 * @dev_mode:		I2C operating role(master/slave).
 * @slave_state:	I2C Slave state(idle/read/write).
 */
struct cdns_i2c {
	struct device		*dev;
	void __iomem *membase;
	struct i2c_adapter adap;
	struct i2c_msg *p_msg;
	int err_status;
	struct completion xfer_done;
	unsigned char *p_send_buf;
	unsigned char *p_recv_buf;
	unsigned int send_count;
	unsigned int recv_count;
	unsigned int curr_recv_count;
	int irq;
	unsigned long input_clk;
	unsigned int i2c_clk;
	unsigned int bus_hold_flag;
	struct clk *clk;
	struct notifier_block clk_rate_change_nb;
	u32 quirks;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
	u16 ctrl_reg_diva_divb;
	struct i2c_client *slave;
	enum cdns_i2c_mode dev_mode;
	enum cdns_i2c_slave_state slave_state;
#endif
};

struct cdns_platform_data {
	u32 quirks;
};

#define to_cdns_i2c(_nb)	container_of(_nb, struct cdns_i2c, \
					     clk_rate_change_nb)

/**
 * cdns_i2c_clear_bus_hold - Clear bus hold bit
 * @id:	Pointer to driver data struct
 *
 * Helper to clear the controller's bus hold bit.
 */
static void cdns_i2c_clear_bus_hold(struct cdns_i2c *id)
{
	u32 reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
	if (reg & CDNS_I2C_CR_HOLD)
		cdns_i2c_writereg(reg & ~CDNS_I2C_CR_HOLD, CDNS_I2C_CR_OFFSET);
}

static inline bool cdns_is_holdquirk(struct cdns_i2c *id, bool hold_wrkaround)
{
	return (hold_wrkaround &&
		(id->curr_recv_count == CDNS_I2C_FIFO_DEPTH + 1));
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static void cdns_i2c_set_mode(enum cdns_i2c_mode mode, struct cdns_i2c *id)
{
	/* Disable all interrupts */
	cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK, CDNS_I2C_IDR_OFFSET);

	/* Clear FIFO and transfer size */
	cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);

	/* Update device mode and state */
	id->dev_mode = mode;
	id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;

	switch (mode) {
	case CDNS_I2C_MODE_MASTER:
		/* Enable i2c master */
		cdns_i2c_writereg(id->ctrl_reg_diva_divb |
				  CDNS_I2C_CR_MASTER_EN_MASK,
				  CDNS_I2C_CR_OFFSET);
		/*
		 * This delay is needed to give the IP some time to switch to
		 * the master mode. With lower values(like 110 us) i2cdetect
		 * will not detect any slave and without this delay, the IP will
		 * trigger a timeout interrupt.
		 */
		usleep_range(115, 125);
		break;
	case CDNS_I2C_MODE_SLAVE:
		/* Enable i2c slave */
		cdns_i2c_writereg(id->ctrl_reg_diva_divb &
				  CDNS_I2C_CR_SLAVE_EN_MASK,
				  CDNS_I2C_CR_OFFSET);

		/* Setting slave address */
		cdns_i2c_writereg(id->slave->addr & CDNS_I2C_ADDR_MASK,
				  CDNS_I2C_ADDR_OFFSET);

		/* Enable slave send/receive interrupts */
		cdns_i2c_writereg(CDNS_I2C_IXR_SLAVE_INTR_MASK,
				  CDNS_I2C_IER_OFFSET);
		break;
	}
}

static void cdns_i2c_slave_rcv_data(struct cdns_i2c *id)
{
	u8 bytes;
	unsigned char data;

	/* Prepare backend for data reception */
	if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
		id->slave_state = CDNS_I2C_SLAVE_STATE_RECV;
		i2c_slave_event(id->slave, I2C_SLAVE_WRITE_REQUESTED, NULL);
	}

	/* Fetch number of bytes to receive */
	bytes = cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);

	/* Read data and send to backend */
	while (bytes--) {
		data = cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
		i2c_slave_event(id->slave, I2C_SLAVE_WRITE_RECEIVED, &data);
	}
}

static void cdns_i2c_slave_send_data(struct cdns_i2c *id)
{
	u8 data;

	/* Prepare backend for data transmission */
	if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
		id->slave_state = CDNS_I2C_SLAVE_STATE_SEND;
		i2c_slave_event(id->slave, I2C_SLAVE_READ_REQUESTED, &data);
	} else {
		i2c_slave_event(id->slave, I2C_SLAVE_READ_PROCESSED, &data);
	}

	/* Send data over bus */
	cdns_i2c_writereg(data, CDNS_I2C_DATA_OFFSET);
}

/**
 * cdns_i2c_slave_isr - Interrupt handler for the I2C device in slave role
 * @ptr:       Pointer to I2C device private data
 *
 * This function handles the data interrupt and transfer complete interrupt of
 * the I2C device in slave role.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_slave_isr(void *ptr)
{
	struct cdns_i2c *id = ptr;
	unsigned int isr_status, i2c_status;

	/* Fetch the interrupt status */
	isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
	cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

	/* Ignore masked interrupts */
	isr_status &= ~cdns_i2c_readreg(CDNS_I2C_IMR_OFFSET);

	/* Fetch transfer mode (send/receive) */
	i2c_status = cdns_i2c_readreg(CDNS_I2C_SR_OFFSET);

	/* Handle data send/receive */
	if (i2c_status & CDNS_I2C_SR_RXRW) {
		/* Send data to master */
		if (isr_status & CDNS_I2C_IXR_DATA)
			cdns_i2c_slave_send_data(id);

		if (isr_status & CDNS_I2C_IXR_COMP) {
			id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
			i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
		}
	} else {
		/* Receive data from master */
		if (isr_status & CDNS_I2C_IXR_DATA)
			cdns_i2c_slave_rcv_data(id);

		if (isr_status & CDNS_I2C_IXR_COMP) {
			cdns_i2c_slave_rcv_data(id);
			id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
			i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
		}
	}

	/* Master indicated xfer stop or fifo underflow/overflow */
	if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_RX_OVF |
			  CDNS_I2C_IXR_RX_UNF | CDNS_I2C_IXR_TX_OVF)) {
		id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
		i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
		cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);
	}

	return IRQ_HANDLED;
}
#endif

/**
 * cdns_i2c_master_isr - Interrupt handler for the I2C device in master role
 * @ptr:       Pointer to I2C device private data
 *
 * This function handles the data interrupt, transfer complete interrupt and
 * the error interrupts of the I2C device in master role.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_master_isr(void *ptr)
{
	unsigned int isr_status, avail_bytes, updatetx;
	unsigned int bytes_to_send;
	bool hold_quirk;
	struct cdns_i2c *id = ptr;
	/* Signal completion only after everything is updated */
	int done_flag = 0;
	irqreturn_t status = IRQ_NONE;

	isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
	cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);
	id->err_status = 0;

	/* Handling nack and arbitration lost interrupt */
	if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_ARB_LOST)) {
		done_flag = 1;
		status = IRQ_HANDLED;
	}

	/*
	 * Check if transfer size register needs to be updated again for a
	 * large data receive operation.
	 */
	updatetx = 0;
	if (id->recv_count > id->curr_recv_count)
		updatetx = 1;

	hold_quirk = (id->quirks & CDNS_I2C_BROKEN_HOLD_BIT) && updatetx;

	/* When receiving, handle data interrupt and completion interrupt */
	if (id->p_recv_buf &&
	    ((isr_status & CDNS_I2C_IXR_COMP) ||
	     (isr_status & CDNS_I2C_IXR_DATA))) {
		/* Read data if receive data valid is set */
		while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
		       CDNS_I2C_SR_RXDV) {
			if (id->recv_count > 0) {
				*(id->p_recv_buf)++ =
					cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
				id->recv_count--;
				id->curr_recv_count--;

				/*
				 * Clear hold bit that was set for FIFO control
				 * if RX data left is less than or equal to
				 * FIFO DEPTH unless repeated start is selected
				 */
				if (id->recv_count <= CDNS_I2C_FIFO_DEPTH &&
				    !id->bus_hold_flag)
					cdns_i2c_clear_bus_hold(id);

			} else {
				dev_err(id->adap.dev.parent,
					"xfer_size reg rollover. xfer aborted!\n");
				id->err_status |= CDNS_I2C_IXR_TO;
				break;
			}

			if (cdns_is_holdquirk(id, hold_quirk))
				break;
		}

		/*
		 * The controller sends NACK to the slave when transfer size
		 * register reaches zero without considering the HOLD bit.
		 * This workaround is implemented for large data transfers to
		 * maintain transfer size non-zero while performing a large
		 * receive operation.
		 */
		if (cdns_is_holdquirk(id, hold_quirk)) {
			/* wait while fifo is full */
			while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
			       (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))
				;

			/*
			 * Check number of bytes to be received against maximum
			 * transfer size and update register accordingly.
			 */
			if (((int)(id->recv_count) - CDNS_I2C_FIFO_DEPTH) >
			    CDNS_I2C_TRANSFER_SIZE) {
				cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
						  CDNS_I2C_XFER_SIZE_OFFSET);
				id->curr_recv_count = CDNS_I2C_TRANSFER_SIZE +
						      CDNS_I2C_FIFO_DEPTH;
			} else {
				cdns_i2c_writereg(id->recv_count -
						  CDNS_I2C_FIFO_DEPTH,
						  CDNS_I2C_XFER_SIZE_OFFSET);
				id->curr_recv_count = id->recv_count;
			}
		} else if (id->recv_count && !hold_quirk &&
						!id->curr_recv_count) {

			/* Set the slave address in address register*/
			cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
						CDNS_I2C_ADDR_OFFSET);

			if (id->recv_count > CDNS_I2C_TRANSFER_SIZE) {
				cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
						CDNS_I2C_XFER_SIZE_OFFSET);
				id->curr_recv_count = CDNS_I2C_TRANSFER_SIZE;
			} else {
				cdns_i2c_writereg(id->recv_count,
						CDNS_I2C_XFER_SIZE_OFFSET);
				id->curr_recv_count = id->recv_count;
			}
		}

		/* Clear hold (if not repeated start) and signal completion */
		if ((isr_status & CDNS_I2C_IXR_COMP) && !id->recv_count) {
			if (!id->bus_hold_flag)
				cdns_i2c_clear_bus_hold(id);
			done_flag = 1;
		}

		status = IRQ_HANDLED;
	}

	/* When sending, handle transfer complete interrupt */
	if ((isr_status & CDNS_I2C_IXR_COMP) && !id->p_recv_buf) {
		/*
		 * If there is more data to be sent, calculate the
		 * space available in FIFO and fill with that many bytes.
		 */
		if (id->send_count) {
			avail_bytes = CDNS_I2C_FIFO_DEPTH -
			    cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
			if (id->send_count > avail_bytes)
				bytes_to_send = avail_bytes;
			else
				bytes_to_send = id->send_count;

			while (bytes_to_send--) {
				cdns_i2c_writereg(
					(*(id->p_send_buf)++),
					 CDNS_I2C_DATA_OFFSET);
				id->send_count--;
			}
		} else {
			/*
			 * Signal the completion of transaction and
			 * clear the hold bus bit if there are no
			 * further messages to be processed.
			 */
			done_flag = 1;
		}
		if (!id->send_count && !id->bus_hold_flag)
			cdns_i2c_clear_bus_hold(id);

		status = IRQ_HANDLED;
	}

	/* Update the status for errors */
	id->err_status |= isr_status & CDNS_I2C_IXR_ERR_INTR_MASK;
	if (id->err_status)
		status = IRQ_HANDLED;

	if (done_flag)
		complete(&id->xfer_done);

	return status;
}

/**
 * cdns_i2c_isr - Interrupt handler for the I2C device
 * @irq:	irq number for the I2C device
 * @ptr:	void pointer to cdns_i2c structure
 *
 * This function passes the control to slave/master based on current role of
 * i2c controller.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
{
#if IS_ENABLED(CONFIG_I2C_SLAVE)
	struct cdns_i2c *id = ptr;

	if (id->dev_mode == CDNS_I2C_MODE_SLAVE)
		return cdns_i2c_slave_isr(ptr);
#endif
	return cdns_i2c_master_isr(ptr);
}

/**
 * cdns_i2c_mrecv - Prepare and start a master receive operation
 * @id:		pointer to the i2c device structure
 */
static void cdns_i2c_mrecv(struct cdns_i2c *id)
{
	unsigned int ctrl_reg;
	unsigned int isr_status;

	id->p_recv_buf = id->p_msg->buf;
	id->recv_count = id->p_msg->len;

	/* Put the controller in master receive mode and clear the FIFO */
	ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
	ctrl_reg |= CDNS_I2C_CR_RW | CDNS_I2C_CR_CLR_FIFO;

	if (id->p_msg->flags & I2C_M_RECV_LEN)
		id->recv_count = I2C_SMBUS_BLOCK_MAX + 1;

	id->curr_recv_count = id->recv_count;

	/*
	 * Check for the message size against FIFO depth and set the
	 * 'hold bus' bit if it is greater than FIFO depth.
	 */
	if (id->recv_count > CDNS_I2C_FIFO_DEPTH)
		ctrl_reg |= CDNS_I2C_CR_HOLD;

	cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);

	/* Clear the interrupts in interrupt status register */
	isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
	cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

	/*
	 * The no. of bytes to receive is checked against the limit of
	 * max transfer size. Set transfer size register with no of bytes
	 * receive if it is less than transfer size and transfer size if
	 * it is more. Enable the interrupts.
	 */
	if (id->recv_count > CDNS_I2C_TRANSFER_SIZE) {
		cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
				  CDNS_I2C_XFER_SIZE_OFFSET);
		id->curr_recv_count = CDNS_I2C_TRANSFER_SIZE;
	} else {
		cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
	}

	/* Set the slave address in address register - triggers operation */
	cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
						CDNS_I2C_ADDR_OFFSET);
	/* Clear the bus hold flag if bytes to receive is less than FIFO size */
	if (!id->bus_hold_flag &&
		((id->p_msg->flags & I2C_M_RECV_LEN) != I2C_M_RECV_LEN) &&
		(id->recv_count <= CDNS_I2C_FIFO_DEPTH))
			cdns_i2c_clear_bus_hold(id);
	cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
}

/**
 * cdns_i2c_msend - Prepare and start a master send operation
 * @id:		pointer to the i2c device
 */
static void cdns_i2c_msend(struct cdns_i2c *id)
{
	unsigned int avail_bytes;
	unsigned int bytes_to_send;
	unsigned int ctrl_reg;
	unsigned int isr_status;

	id->p_recv_buf = NULL;
	id->p_send_buf = id->p_msg->buf;
	id->send_count = id->p_msg->len;

	/* Set the controller in Master transmit mode and clear the FIFO. */
	ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
	ctrl_reg &= ~CDNS_I2C_CR_RW;
	ctrl_reg |= CDNS_I2C_CR_CLR_FIFO;

	/*
	 * Check for the message size against FIFO depth and set the
	 * 'hold bus' bit if it is greater than FIFO depth.
	 */
	if (id->send_count > CDNS_I2C_FIFO_DEPTH)
		ctrl_reg |= CDNS_I2C_CR_HOLD;
	cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);

	/* Clear the interrupts in interrupt status register. */
	isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
	cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

	/*
	 * Calculate the space available in FIFO. Check the message length
	 * against the space available, and fill the FIFO accordingly.
	 * Enable the interrupts.
	 */
	avail_bytes = CDNS_I2C_FIFO_DEPTH -
				cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);

	if (id->send_count > avail_bytes)
		bytes_to_send = avail_bytes;
	else
		bytes_to_send = id->send_count;

	while (bytes_to_send--) {
		cdns_i2c_writereg((*(id->p_send_buf)++), CDNS_I2C_DATA_OFFSET);
		id->send_count--;
	}

	/*
	 * Clear the bus hold flag if there is no more data
	 * and if it is the last message.
	 */
	if (!id->bus_hold_flag && !id->send_count)
		cdns_i2c_clear_bus_hold(id);
	/* Set the slave address in address register - triggers operation. */
	cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
						CDNS_I2C_ADDR_OFFSET);

	cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
}

/**
 * cdns_i2c_master_reset - Reset the interface
 * @adap:	pointer to the i2c adapter driver instance
 *
 * This function cleanup the fifos, clear the hold bit and status
 * and disable the interrupts.
 */
static void cdns_i2c_master_reset(struct i2c_adapter *adap)
{
	struct cdns_i2c *id = adap->algo_data;
	u32 regval;

	/* Disable the interrupts */
	cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK, CDNS_I2C_IDR_OFFSET);
	/* Clear the hold bit and fifos */
	regval = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
	regval &= ~CDNS_I2C_CR_HOLD;
	regval |= CDNS_I2C_CR_CLR_FIFO;
	cdns_i2c_writereg(regval, CDNS_I2C_CR_OFFSET);
	/* Update the transfercount register to zero */
	cdns_i2c_writereg(0, CDNS_I2C_XFER_SIZE_OFFSET);
	/* Clear the interrupt status register */
	regval = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
	cdns_i2c_writereg(regval, CDNS_I2C_ISR_OFFSET);
	/* Clear the status register */
	regval = cdns_i2c_readreg(CDNS_I2C_SR_OFFSET);
	cdns_i2c_writereg(regval, CDNS_I2C_SR_OFFSET);
}

static int cdns_i2c_process_msg(struct cdns_i2c *id, struct i2c_msg *msg,
		struct i2c_adapter *adap)
{
	unsigned long time_left;
	u32 reg;

	id->p_msg = msg;
	id->err_status = 0;
	reinit_completion(&id->xfer_done);

	/* Check for the TEN Bit mode on each msg */
	reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
	if (msg->flags & I2C_M_TEN) {
		if (reg & CDNS_I2C_CR_NEA)
			cdns_i2c_writereg(reg & ~CDNS_I2C_CR_NEA,
					CDNS_I2C_CR_OFFSET);
	} else {
		if (!(reg & CDNS_I2C_CR_NEA))
			cdns_i2c_writereg(reg | CDNS_I2C_CR_NEA,
					CDNS_I2C_CR_OFFSET);
	}

	/* Check for the R/W flag on each msg */
	if (msg->flags & I2C_M_RD)
		cdns_i2c_mrecv(id);
	else
		cdns_i2c_msend(id);

	/* Wait for the signal of completion */
	time_left = wait_for_completion_timeout(&id->xfer_done, adap->timeout);
	if (time_left == 0) {
		cdns_i2c_master_reset(adap);
		dev_err(id->adap.dev.parent,
				"timeout waiting on completion\n");
		return -ETIMEDOUT;
	}

	cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK,
			  CDNS_I2C_IDR_OFFSET);

	/* If it is bus arbitration error, try again */
	if (id->err_status & CDNS_I2C_IXR_ARB_LOST)
		return -EAGAIN;

	return 0;
}

/**
 * cdns_i2c_master_xfer - The main i2c transfer function
 * @adap:	pointer to the i2c adapter driver instance
 * @msgs:	pointer to the i2c message structure
 * @num:	the number of messages to transfer
 *
 * Initiates the send/recv activity based on the transfer message received.
 *
 * Return: number of msgs processed on success, negative error otherwise
 */
static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
				int num)
{
	int ret, count;
	u32 reg;
	struct cdns_i2c *id = adap->algo_data;
	bool hold_quirk;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
	bool change_role = false;
#endif

	ret = pm_runtime_resume_and_get(id->dev);
	if (ret < 0)
		return ret;

#if IS_ENABLED(CONFIG_I2C_SLAVE)
	/* Check i2c operating mode and switch if possible */
	if (id->dev_mode == CDNS_I2C_MODE_SLAVE) {
		if (id->slave_state != CDNS_I2C_SLAVE_STATE_IDLE)
			return -EAGAIN;

		/* Set mode to master */
		cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);

		/* Mark flag to change role once xfer is completed */
		change_role = true;
	}
#endif

	/* Check if the bus is free */
	if (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) & CDNS_I2C_SR_BA) {
		ret = -EAGAIN;
		goto out;
	}

	hold_quirk = !!(id->quirks & CDNS_I2C_BROKEN_HOLD_BIT);
	/*
	 * Set the flag to one when multiple messages are to be
	 * processed with a repeated start.
	 */
	if (num > 1) {
		/*
		 * This controller does not give completion interrupt after a
		 * master receive message if HOLD bit is set (repeated start),
		 * resulting in SW timeout. Hence, if a receive message is
		 * followed by any other message, an error is returned
		 * indicating that this sequence is not supported.
		 */
		for (count = 0; (count < num - 1 && hold_quirk); count++) {
			if (msgs[count].flags & I2C_M_RD) {
				dev_warn(adap->dev.parent,
					 "Can't do repeated start after a receive message\n");
				ret = -EOPNOTSUPP;
				goto out;
			}
		}
		id->bus_hold_flag = 1;
		reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
		reg |= CDNS_I2C_CR_HOLD;
		cdns_i2c_writereg(reg, CDNS_I2C_CR_OFFSET);
	} else {
		id->bus_hold_flag = 0;
	}

	/* Process the msg one by one */
	for (count = 0; count < num; count++, msgs++) {
		if (count == (num - 1))
			id->bus_hold_flag = 0;

		ret = cdns_i2c_process_msg(id, msgs, adap);
		if (ret)
			goto out;

		/* Report the other error interrupts to application */
		if (id->err_status) {
			cdns_i2c_master_reset(adap);

			if (id->err_status & CDNS_I2C_IXR_NACK) {
				ret = -ENXIO;
				goto out;
			}
			ret = -EIO;
			goto out;
		}
	}

	ret = num;

out:

#if IS_ENABLED(CONFIG_I2C_SLAVE)
	/* Switch i2c mode to slave */
	if (change_role)
		cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);
#endif

	pm_runtime_mark_last_busy(id->dev);
	pm_runtime_put_autosuspend(id->dev);
	return ret;
}

/**
 * cdns_i2c_func - Returns the supported features of the I2C driver
 * @adap:	pointer to the i2c adapter structure
 *
 * Return: 32 bit value, each bit corresponding to a feature
 */
static u32 cdns_i2c_func(struct i2c_adapter *adap)
{
	u32 func = I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR |
			(I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) |
			I2C_FUNC_SMBUS_BLOCK_DATA;

#if IS_ENABLED(CONFIG_I2C_SLAVE)
	func |= I2C_FUNC_SLAVE;
#endif

	return func;
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static int cdns_reg_slave(struct i2c_client *slave)
{
	int ret;
	struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
									adap);

	if (id->slave)
		return -EBUSY;

	if (slave->flags & I2C_CLIENT_TEN)
		return -EAFNOSUPPORT;

	ret = pm_runtime_resume_and_get(id->dev);
	if (ret < 0)
		return ret;

	/* Store slave information */
	id->slave = slave;

	/* Enable I2C slave */
	cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);

	return 0;
}

static int cdns_unreg_slave(struct i2c_client *slave)
{
	struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
									adap);

	pm_runtime_put(id->dev);

	/* Remove slave information */
	id->slave = NULL;

	/* Enable I2C master */
	cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);

	return 0;
}
#endif

static const struct i2c_algorithm cdns_i2c_algo = {
	.master_xfer	= cdns_i2c_master_xfer,
	.functionality	= cdns_i2c_func,
#if IS_ENABLED(CONFIG_I2C_SLAVE)
	.reg_slave	= cdns_reg_slave,
	.unreg_slave	= cdns_unreg_slave,
#endif
};

/**
 * cdns_i2c_calc_divs - Calculate clock dividers
 * @f:		I2C clock frequency
 * @input_clk:	Input clock frequency
 * @a:		First divider (return value)
 * @b:		Second divider (return value)
 *
 * f is used as input and output variable. As input it is used as target I2C
 * frequency. On function exit f holds the actually resulting I2C frequency.
 *
 * Return: 0 on success, negative errno otherwise.
 */
static int cdns_i2c_calc_divs(unsigned long *f, unsigned long input_clk,
		unsigned int *a, unsigned int *b)
{
	unsigned long fscl = *f, best_fscl = *f, actual_fscl, temp;
	unsigned int div_a, div_b, calc_div_a = 0, calc_div_b = 0;
	unsigned int last_error, current_error;

	/* calculate (divisor_a+1) x (divisor_b+1) */
	temp = input_clk / (22 * fscl);

	/*
	 * If the calculated value is negative or 0, the fscl input is out of
	 * range. Return error.
	 */
	if (!temp || (temp > (CDNS_I2C_DIVA_MAX * CDNS_I2C_DIVB_MAX)))
		return -EINVAL;

	last_error = -1;
	for (div_a = 0; div_a < CDNS_I2C_DIVA_MAX; div_a++) {
		div_b = DIV_ROUND_UP(input_clk, 22 * fscl * (div_a + 1));

		if ((div_b < 1) || (div_b > CDNS_I2C_DIVB_MAX))
			continue;
		div_b--;

		actual_fscl = input_clk / (22 * (div_a + 1) * (div_b + 1));

		if (actual_fscl > fscl)
			continue;

		current_error = ((actual_fscl > fscl) ? (actual_fscl - fscl) :
							(fscl - actual_fscl));

		if (last_error > current_error) {
			calc_div_a = div_a;
			calc_div_b = div_b;