u-boot-brain/drivers/i2c/designware_i2c.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2009
 * Vipin Kumar, ST Micoelectronics, vipin.kumar@st.com.
 */

#include <common.h>
#include <clk.h>
#include <dm.h>
#include <i2c.h>
#include <pci.h>
#include <reset.h>
#include <asm/io.h>
#include "designware_i2c.h"

#ifdef CONFIG_SYS_I2C_DW_ENABLE_STATUS_UNSUPPORTED
static int  dw_i2c_enable(struct i2c_regs *i2c_base, bool enable)
{
	u32 ena = enable ? IC_ENABLE_0B : 0;

	writel(ena, &i2c_base->ic_enable);

	return 0;
}
#else
static int dw_i2c_enable(struct i2c_regs *i2c_base, bool enable)
{
	u32 ena = enable ? IC_ENABLE_0B : 0;
	int timeout = 100;

	do {
		writel(ena, &i2c_base->ic_enable);
		if ((readl(&i2c_base->ic_enable_status) & IC_ENABLE_0B) == ena)
			return 0;

		/*
		 * Wait 10 times the signaling period of the highest I2C
		 * transfer supported by the driver (for 400KHz this is
		 * 25us) as described in the DesignWare I2C databook.
		 */
		udelay(25);
	} while (timeout--);
	printf("timeout in %sabling I2C adapter\n", enable ? "en" : "dis");

	return -ETIMEDOUT;
}
#endif

/* High and low times in different speed modes (in ns) */
enum {
	/* SDA Hold Time */
	DEFAULT_SDA_HOLD_TIME		= 300,
};

/**
 * calc_counts() - Convert a period to a number of IC clk cycles
 *
 * @ic_clk: Input clock in Hz
 * @period_ns: Period to represent, in ns
 * @return calculated count
 */
static uint calc_counts(uint ic_clk, uint period_ns)
{
	return DIV_ROUND_UP(ic_clk / 1000 * period_ns, NANO_TO_KILO);
}

/**
 * struct i2c_mode_info - Information about an I2C speed mode
 *
 * Each speed mode has its own characteristics. This struct holds these to aid
 * calculations in dw_i2c_calc_timing().
 *
 * @speed: Speed in Hz
 * @min_scl_lowtime_ns: Minimum value for SCL low period in ns
 * @min_scl_hightime_ns: Minimum value for SCL high period in ns
 * @def_rise_time_ns: Default rise time in ns
 * @def_fall_time_ns: Default fall time in ns
 */
struct i2c_mode_info {
	int speed;
	int min_scl_hightime_ns;
	int min_scl_lowtime_ns;
	int def_rise_time_ns;
	int def_fall_time_ns;
};

static const struct i2c_mode_info info_for_mode[] = {
	[IC_SPEED_MODE_STANDARD] = {
		I2C_SPEED_STANDARD_RATE,
		MIN_SS_SCL_HIGHTIME,
		MIN_SS_SCL_LOWTIME,
		1000,
		300,
	},
	[IC_SPEED_MODE_FAST] = {
		I2C_SPEED_FAST_RATE,
		MIN_FS_SCL_HIGHTIME,
		MIN_FS_SCL_LOWTIME,
		300,
		300,
	},
	[IC_SPEED_MODE_FAST_PLUS] = {
		I2C_SPEED_FAST_PLUS_RATE,
		MIN_FP_SCL_HIGHTIME,
		MIN_FP_SCL_LOWTIME,
		260,
		500,
	},
	[IC_SPEED_MODE_HIGH] = {
		I2C_SPEED_HIGH_RATE,
		MIN_HS_SCL_HIGHTIME,
		MIN_HS_SCL_LOWTIME,
		120,
		120,
	},
};

/**
 * dw_i2c_calc_timing() - Calculate the timings to use for a bus
 *
 * @priv: Bus private information (NULL if not using driver model)
 * @mode: Speed mode to use
 * @ic_clk: IC clock speed in Hz
 * @spk_cnt: Spike-suppression count
 * @config: Returns value to use
 * @return 0 if OK, -EINVAL if the calculation failed due to invalid data
 */
static int dw_i2c_calc_timing(struct dw_i2c *priv, enum i2c_speed_mode mode,
			      int ic_clk, int spk_cnt,
			      struct dw_i2c_speed_config *config)
{
	int fall_cnt, rise_cnt, min_tlow_cnt, min_thigh_cnt;
	int hcnt, lcnt, period_cnt, diff, tot;
	int sda_hold_time_ns, scl_rise_time_ns, scl_fall_time_ns;
	const struct i2c_mode_info *info;

	/*
	 * Find the period, rise, fall, min tlow, and min thigh in terms of
	 * counts of the IC clock
	 */
	info = &info_for_mode[mode];
	period_cnt = ic_clk / info->speed;
	scl_rise_time_ns = priv && priv->scl_rise_time_ns ?
		 priv->scl_rise_time_ns : info->def_rise_time_ns;
	scl_fall_time_ns = priv && priv->scl_fall_time_ns ?
		 priv->scl_fall_time_ns : info->def_fall_time_ns;
	rise_cnt = calc_counts(ic_clk, scl_rise_time_ns);
	fall_cnt = calc_counts(ic_clk, scl_fall_time_ns);
	min_tlow_cnt = calc_counts(ic_clk, info->min_scl_lowtime_ns);
	min_thigh_cnt = calc_counts(ic_clk, info->min_scl_hightime_ns);

	debug("dw_i2c: period %d rise %d fall %d tlow %d thigh %d spk %d\n",
	      period_cnt, rise_cnt, fall_cnt, min_tlow_cnt, min_thigh_cnt,
	      spk_cnt);

	/*
	 * Back-solve for hcnt and lcnt according to the following equations:
	 * SCL_High_time = [(HCNT + IC_*_SPKLEN + 7) * ic_clk] + SCL_Fall_time
	 * SCL_Low_time = [(LCNT + 1) * ic_clk] - SCL_Fall_time + SCL_Rise_time
	 */
	hcnt = min_thigh_cnt - fall_cnt - 7 - spk_cnt;
	lcnt = min_tlow_cnt - rise_cnt + fall_cnt - 1;

	if (hcnt < 0 || lcnt < 0) {
		debug("dw_i2c: bad counts. hcnt = %d lcnt = %d\n", hcnt, lcnt);
		return -EINVAL;
	}

	/*
	 * Now add things back up to ensure the period is hit. If it is off,
	 * split the difference and bias to lcnt for remainder
	 */
	tot = hcnt + lcnt + 7 + spk_cnt + rise_cnt + 1;

	if (tot < period_cnt) {
		diff = (period_cnt - tot) / 2;
		hcnt += diff;
		lcnt += diff;
		tot = hcnt + lcnt + 7 + spk_cnt + rise_cnt + 1;
		lcnt += period_cnt - tot;
	}

	config->scl_lcnt = lcnt;
	config->scl_hcnt = hcnt;

	/* Use internal default unless other value is specified */
	sda_hold_time_ns = priv && priv->sda_hold_time_ns ?
		 priv->sda_hold_time_ns : DEFAULT_SDA_HOLD_TIME;
	config->sda_hold = calc_counts(ic_clk, sda_hold_time_ns);

	debug("dw_i2c: hcnt = %d lcnt = %d sda hold = %d\n", hcnt, lcnt,
	      config->sda_hold);

	return 0;
}

static int calc_bus_speed(struct dw_i2c *priv, int speed, ulong bus_clk,
			  struct dw_i2c_speed_config *config)
{
	const struct dw_scl_sda_cfg *scl_sda_cfg = NULL;
	struct i2c_regs *regs = priv->regs;
	enum i2c_speed_mode i2c_spd;
	int spk_cnt;
	int ret;

	if (priv)
		scl_sda_cfg = priv->scl_sda_cfg;
	/* Allow high speed if there is no config, or the config allows it */
	if (speed >= I2C_SPEED_HIGH_RATE &&
	    (!scl_sda_cfg || scl_sda_cfg->has_high_speed))
		i2c_spd = IC_SPEED_MODE_HIGH;
	else if (speed >= I2C_SPEED_FAST_RATE)
		i2c_spd = IC_SPEED_MODE_FAST_PLUS;
	else if (speed >= I2C_SPEED_FAST_PLUS_RATE)
		i2c_spd = IC_SPEED_MODE_FAST;
	else
		i2c_spd = IC_SPEED_MODE_STANDARD;

	/* Get the proper spike-suppression count based on target speed */
	if (!priv || !priv->has_spk_cnt)
		spk_cnt = 0;
	else if (i2c_spd >= IC_SPEED_MODE_HIGH)
		spk_cnt = readl(&regs->hs_spklen);
	else
		spk_cnt = readl(&regs->fs_spklen);
	if (scl_sda_cfg) {
		config->sda_hold = scl_sda_cfg->sda_hold;
		if (i2c_spd == IC_SPEED_MODE_STANDARD) {
			config->scl_hcnt = scl_sda_cfg->ss_hcnt;
			config->scl_lcnt = scl_sda_cfg->ss_lcnt;
		} else {
			config->scl_hcnt = scl_sda_cfg->fs_hcnt;
			config->scl_lcnt = scl_sda_cfg->fs_lcnt;
		}
	} else {
		ret = dw_i2c_calc_timing(priv, i2c_spd, bus_clk, spk_cnt,
					 config);
		if (ret)
			return log_msg_ret("gen_confg", ret);
	}
	config->speed_mode = i2c_spd;

	return 0;
}

/*
 * _dw_i2c_set_bus_speed - Set the i2c speed
 * @speed:	required i2c speed
 *
 * Set the i2c speed.
 */
static int _dw_i2c_set_bus_speed(struct dw_i2c *priv, struct i2c_regs *i2c_base,
				 unsigned int speed, unsigned int bus_clk)
{
	struct dw_i2c_speed_config config;
	unsigned int cntl;
	unsigned int ena;
	int ret;

	ret = calc_bus_speed(priv, speed, bus_clk, &config);
	if (ret)
		return ret;

	/* Get enable setting for restore later */
	ena = readl(&i2c_base->ic_enable) & IC_ENABLE_0B;

	/* to set speed cltr must be disabled */
	dw_i2c_enable(i2c_base, false);

	cntl = (readl(&i2c_base->ic_con) & (~IC_CON_SPD_MSK));

	switch (config.speed_mode) {
	case IC_SPEED_MODE_HIGH:
		cntl |= IC_CON_SPD_SS;
		writel(config.scl_hcnt, &i2c_base->ic_hs_scl_hcnt);
		writel(config.scl_lcnt, &i2c_base->ic_hs_scl_lcnt);
		break;
	case IC_SPEED_MODE_STANDARD:
		cntl |= IC_CON_SPD_SS;
		writel(config.scl_hcnt, &i2c_base->ic_ss_scl_hcnt);
		writel(config.scl_lcnt, &i2c_base->ic_ss_scl_lcnt);
		break;
	case IC_SPEED_MODE_FAST_PLUS:
	case IC_SPEED_MODE_FAST:
	default:
		cntl |= IC_CON_SPD_FS;
		writel(config.scl_hcnt, &i2c_base->ic_fs_scl_hcnt);
		writel(config.scl_lcnt, &i2c_base->ic_fs_scl_lcnt);
		break;
	}

	writel(cntl, &i2c_base->ic_con);

	/* Configure SDA Hold Time if required */
	if (config.sda_hold)
		writel(config.sda_hold, &i2c_base->ic_sda_hold);

	/* Restore back i2c now speed set */
	if (ena == IC_ENABLE_0B)
		dw_i2c_enable(i2c_base, true);

	return 0;
}

/*
 * i2c_setaddress - Sets the target slave address
 * @i2c_addr:	target i2c address
 *
 * Sets the target slave address.
 */
static void i2c_setaddress(struct i2c_regs *i2c_base, unsigned int i2c_addr)
{
	/* Disable i2c */
	dw_i2c_enable(i2c_base, false);

	writel(i2c_addr, &i2c_base->ic_tar);

	/* Enable i2c */
	dw_i2c_enable(i2c_base, true);
}

/*
 * i2c_flush_rxfifo - Flushes the i2c RX FIFO
 *
 * Flushes the i2c RX FIFO
 */
static void i2c_flush_rxfifo(struct i2c_regs *i2c_base)
{
	while (readl(&i2c_base->ic_status) & IC_STATUS_RFNE)
		readl(&i2c_base->ic_cmd_data);
}

/*
 * i2c_wait_for_bb - Waits for bus busy
 *
 * Waits for bus busy
 */
static int i2c_wait_for_bb(struct i2c_regs *i2c_base)
{
	unsigned long start_time_bb = get_timer(0);

	while ((readl(&i2c_base->ic_status) & IC_STATUS_MA) ||
	       !(readl(&i2c_base->ic_status) & IC_STATUS_TFE)) {

		/* Evaluate timeout */
		if (get_timer(start_time_bb) > (unsigned long)(I2C_BYTE_TO_BB))
			return 1;
	}

	return 0;
}

static int i2c_xfer_init(struct i2c_regs *i2c_base, uchar chip, uint addr,
			 int alen)
{
	if (i2c_wait_for_bb(i2c_base))
		return 1;

	i2c_setaddress(i2c_base, chip);
	while (alen) {
		alen--;
		/* high byte address going out first */
		writel((addr >> (alen * 8)) & 0xff,
		       &i2c_base->ic_cmd_data);
	}
	return 0;
}

static int i2c_xfer_finish(struct i2c_regs *i2c_base)
{
	ulong start_stop_det = get_timer(0);

	while (1) {
		if ((readl(&i2c_base->ic_raw_intr_stat) & IC_STOP_DET)) {
			readl(&i2c_base->ic_clr_stop_det);
			break;
		} else if (get_timer(start_stop_det) > I2C_STOPDET_TO) {
			break;
		}
	}

	if (i2c_wait_for_bb(i2c_base)) {
		printf("Timed out waiting for bus\n");
		return 1;
	}

	i2c_flush_rxfifo(i2c_base);

	return 0;
}

/*
 * i2c_read - Read from i2c memory
 * @chip:	target i2c address
 * @addr:	address to read from
 * @alen:
 * @buffer:	buffer for read data
 * @len:	no of bytes to be read
 *
 * Read from i2c memory.
 */
static int __dw_i2c_read(struct i2c_regs *i2c_base, u8 dev, uint addr,
			 int alen, u8 *buffer, int len)
{
	unsigned long start_time_rx;
	unsigned int active = 0;

#ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
	/*
	 * EEPROM chips that implement "address overflow" are ones
	 * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
	 * address and the extra bits end up in the "chip address"
	 * bit slots. This makes a 24WC08 (1Kbyte) chip look like
	 * four 256 byte chips.
	 *
	 * Note that we consider the length of the address field to
	 * still be one byte because the extra address bits are
	 * hidden in the chip address.
	 */
	dev |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
	addr &= ~(CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW << (alen * 8));

	debug("%s: fix addr_overflow: dev %02x addr %02x\n", __func__, dev,
	      addr);
#endif

	if (i2c_xfer_init(i2c_base, dev, addr, alen))
		return 1;

	start_time_rx = get_timer(0);
	while (len) {
		if (!active) {
			/*
			 * Avoid writing to ic_cmd_data multiple times
			 * in case this loop spins too quickly and the
			 * ic_status RFNE bit isn't set after the first
			 * write. Subsequent writes to ic_cmd_data can
			 * trigger spurious i2c transfer.
			 */
			if (len == 1)
				writel(IC_CMD | IC_STOP, &i2c_base->ic_cmd_data);
			else
				writel(IC_CMD, &i2c_base->ic_cmd_data);
			active = 1;
		}

		if (readl(&i2c_base->ic_status) & IC_STATUS_RFNE) {
			*buffer++ = (uchar)readl(&i2c_base->ic_cmd_data);
			len--;
			start_time_rx = get_timer(0);
			active = 0;
		} else if (get_timer(start_time_rx) > I2C_BYTE_TO) {
			return 1;
		}
	}

	return i2c_xfer_finish(i2c_base);
}

/*
 * i2c_write - Write to i2c memory
 * @chip:	target i2c address
 * @addr:	address to read from
 * @alen:
 * @buffer:	buffer for read data
 * @len:	no of bytes to be read
 *
 * Write to i2c memory.
 */
static int __dw_i2c_write(struct i2c_regs *i2c_base, u8 dev, uint addr,
			  int alen, u8 *buffer, int len)
{
	int nb = len;
	unsigned long start_time_tx;

#ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
	/*
	 * EEPROM chips that implement "address overflow" are ones
	 * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
	 * address and the extra bits end up in the "chip address"
	 * bit slots. This makes a 24WC08 (1Kbyte) chip look like
	 * four 256 byte chips.
	 *
	 * Note that we consider the length of the address field to
	 * still be one byte because the extra address bits are
	 * hidden in the chip address.
	 */
	dev |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
	addr &= ~(CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW << (alen * 8));

	debug("%s: fix addr_overflow: dev %02x addr %02x\n", __func__, dev,
	      addr);
#endif

	if (i2c_xfer_init(i2c_base, dev, addr, alen))
		return 1;

	start_time_tx = get_timer(0);
	while (len) {
		if (readl(&i2c_base->ic_status) & IC_STATUS_TFNF) {
			if (--len == 0) {
				writel(*buffer | IC_STOP,
				       &i2c_base->ic_cmd_data);
			} else {
				writel(*buffer, &i2c_base->ic_cmd_data);
			}
			buffer++;
			start_time_tx = get_timer(0);

		} else if (get_timer(start_time_tx) > (nb * I2C_BYTE_TO)) {
				printf("Timed out. i2c write Failed\n");
				return 1;
		}
	}

	return i2c_xfer_finish(i2c_base);
}

/*
 * __dw_i2c_init - Init function
 * @speed:	required i2c speed
 * @slaveaddr:	slave address for the device
 *
 * Initialization function.
 */
static int __dw_i2c_init(struct i2c_regs *i2c_base, int speed, int slaveaddr)
{
	int ret;

	/* Disable i2c */
	ret = dw_i2c_enable(i2c_base, false);
	if (ret)
		return ret;

	writel(IC_CON_SD | IC_CON_RE | IC_CON_SPD_FS | IC_CON_MM,
	       &i2c_base->ic_con);
	writel(IC_RX_TL, &i2c_base->ic_rx_tl);
	writel(IC_TX_TL, &i2c_base->ic_tx_tl);
	writel(IC_STOP_DET, &i2c_base->ic_intr_mask);
#ifndef CONFIG_DM_I2C
	_dw_i2c_set_bus_speed(NULL, i2c_base, speed, IC_CLK);
	writel(slaveaddr, &i2c_base->ic_sar);
#endif

	/* Enable i2c */
	ret = dw_i2c_enable(i2c_base, true);
	if (ret)
		return ret;

	return 0;
}

#ifndef CONFIG_DM_I2C
/*
 * The legacy I2C functions. These need to get removed once
 * all users of this driver are converted to DM.
 */
static struct i2c_regs *i2c_get_base(struct i2c_adapter *adap)
{
	switch (adap->hwadapnr) {
#if CONFIG_SYS_I2C_BUS_MAX >= 4
	case 3:
		return (struct i2c_regs *)CONFIG_SYS_I2C_BASE3;
#endif
#if CONFIG_SYS_I2C_BUS_MAX >= 3
	case 2:
		return (struct i2c_regs *)CONFIG_SYS_I2C_BASE2;
#endif
#if CONFIG_SYS_I2C_BUS_MAX >= 2
	case 1:
		return (struct i2c_regs *)CONFIG_SYS_I2C_BASE1;
#endif
	case 0:
		return (struct i2c_regs *)CONFIG_SYS_I2C_BASE;
	default:
		printf("Wrong I2C-adapter number %d\n", adap->hwadapnr);
	}

	return NULL;
}

static unsigned int dw_i2c_set_bus_speed(struct i2c_adapter *adap,
					 unsigned int speed)
{
	adap->speed = speed;
	return _dw_i2c_set_bus_speed(NULL, i2c_get_base(adap), speed, IC_CLK);
}

static void dw_i2c_init(struct i2c_adapter *adap, int speed, int slaveaddr)
{
	__dw_i2c_init(i2c_get_base(adap), speed, slaveaddr);
}

static int dw_i2c_read(struct i2c_adapter *adap, u8 dev, uint addr,
		       int alen, u8 *buffer, int len)
{
	return __dw_i2c_read(i2c_get_base(adap), dev, addr, alen, buffer, len);
}

static int dw_i2c_write(struct i2c_adapter *adap, u8 dev, uint addr,
			int alen, u8 *buffer, int len)
{
	return __dw_i2c_write(i2c_get_base(adap), dev, addr, alen, buffer, len);
}

/* dw_i2c_probe - Probe the i2c chip */
static int dw_i2c_probe(struct i2c_adapter *adap, u8 dev)
{
	struct i2c_regs *i2c_base = i2c_get_base(adap);
	u32 tmp;
	int ret;

	/*
	 * Try to read the first location of the chip.
	 */
	ret = __dw_i2c_read(i2c_base, dev, 0, 1, (uchar *)&tmp, 1);
	if (ret)
		dw_i2c_init(adap, adap->speed, adap->slaveaddr);

	return ret;
}

U_BOOT_I2C_ADAP_COMPLETE(dw_0, dw_i2c_init, dw_i2c_probe, dw_i2c_read,
			 dw_i2c_write, dw_i2c_set_bus_speed,
			 CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE, 0)

#if CONFIG_SYS_I2C_BUS_MAX >= 2
U_BOOT_I2C_ADAP_COMPLETE(dw_1, dw_i2c_init, dw_i2c_probe, dw_i2c_read,
			 dw_i2c_write, dw_i2c_set_bus_speed,
			 CONFIG_SYS_I2C_SPEED1, CONFIG_SYS_I2C_SLAVE1, 1)
#endif

#if CONFIG_SYS_I2C_BUS_MAX >= 3
U_BOOT_I2C_ADAP_COMPLETE(dw_2, dw_i2c_init, dw_i2c_probe, dw_i2c_read,
			 dw_i2c_write, dw_i2c_set_bus_speed,
			 CONFIG_SYS_I2C_SPEED2, CONFIG_SYS_I2C_SLAVE2, 2)
#endif

#if CONFIG_SYS_I2C_BUS_MAX >= 4
U_BOOT_I2C_ADAP_COMPLETE(dw_3, dw_i2c_init, dw_i2c_probe, dw_i2c_read,
			 dw_i2c_write, dw_i2c_set_bus_speed,
			 CONFIG_SYS_I2C_SPEED3, CONFIG_SYS_I2C_SLAVE3, 3)
#endif

#else /* CONFIG_DM_I2C */
/* The DM I2C functions */

static int designware_i2c_xfer(struct udevice *bus, struct i2c_msg *msg,
			       int nmsgs)
{
	struct dw_i2c *i2c = dev_get_priv(bus);
	int ret;

	debug("i2c_xfer: %d messages\n", nmsgs);
	for (; nmsgs > 0; nmsgs--, msg++) {
		debug("i2c_xfer: chip=0x%x, len=0x%x\n", msg->addr, msg->len);
		if (msg->flags & I2C_M_RD) {
			ret = __dw_i2c_read(i2c->regs, msg->addr, 0, 0,
					    msg->buf, msg->len);
		} else {
			ret = __dw_i2c_write(i2c->regs, msg->addr, 0, 0,
					     msg->buf, msg->len);
		}
		if (ret) {
			debug("i2c_write: error sending\n");
			return -EREMOTEIO;
		}
	}

	return 0;
}

static int designware_i2c_set_bus_speed(struct udevice *bus, unsigned int speed)
{
	struct dw_i2c *i2c = dev_get_priv(bus);
	ulong rate;

#if CONFIG_IS_ENABLED(CLK)
	rate = clk_get_rate(&i2c->clk);
	if (IS_ERR_VALUE(rate))
		return -EINVAL;
#else
	rate = IC_CLK;
#endif
	return _dw_i2c_set_bus_speed(i2c, i2c->regs, speed, rate);
}

static int designware_i2c_probe_chip(struct udevice *bus, uint chip_addr,
				     uint chip_flags)
{
	struct dw_i2c *i2c = dev_get_priv(bus);
	struct i2c_regs *i2c_base = i2c->regs;
	u32 tmp;
	int ret;

	/* Try to read the first location of the chip */
	ret = __dw_i2c_read(i2c_base, chip_addr, 0, 1, (uchar *)&tmp, 1);
	if (ret)
		__dw_i2c_init(i2c_base, 0, 0);

	return ret;
}

int designware_i2c_ofdata_to_platdata(struct udevice *bus)
{
	struct dw_i2c *priv = dev_get_priv(bus);

	if (!priv->regs)
		priv->regs = (struct i2c_regs *)devfdt_get_addr_ptr(bus);
	dev_read_u32(bus, "i2c-scl-rising-time-ns", &priv->scl_rise_time_ns);
	dev_read_u32(bus, "i2c-scl-falling-time-ns", &priv->scl_fall_time_ns);
	dev_read_u32(bus, "i2c-sda-hold-time-ns", &priv->sda_hold_time_ns);

	return 0;
}

int designware_i2c_probe(struct udevice *bus)
{
	struct dw_i2c *priv = dev_get_priv(bus);
	int ret;

	ret = reset_get_bulk(bus, &priv->resets);
	if (ret)
		dev_warn(bus, "Can't get reset: %d\n", ret);
	else
		reset_deassert_bulk(&priv->resets);

#if CONFIG_IS_ENABLED(CLK)
	ret = clk_get_by_index(bus, 0, &priv->clk);
	if (ret)
		return ret;

	ret = clk_enable(&priv->clk);
	if (ret && ret != -ENOSYS && ret != -ENOTSUPP) {
		clk_free(&priv->clk);
		dev_err(bus, "failed to enable clock\n");
		return ret;
	}
#endif

	return __dw_i2c_init(priv->regs, 0, 0);
}

int designware_i2c_remove(struct udevice *dev)
{
	struct dw_i2c *priv = dev_get_priv(dev);

#if CONFIG_IS_ENABLED(CLK)
	clk_disable(&priv->clk);
	clk_free(&priv->clk);
#endif

	return reset_release_bulk(&priv->resets);
}

const struct dm_i2c_ops designware_i2c_ops = {
	.xfer		= designware_i2c_xfer,
	.probe_chip	= designware_i2c_probe_chip,
	.set_bus_speed	= designware_i2c_set_bus_speed,
};

static const struct udevice_id designware_i2c_ids[] = {
	{ .compatible = "snps,designware-i2c" },
	{ }
};

U_BOOT_DRIVER(i2c_designware) = {
	.name	= "i2c_designware",
	.id	= UCLASS_I2C,
	.of_match = designware_i2c_ids,
	.ofdata_to_platdata = designware_i2c_ofdata_to_platdata,
	.probe	= designware_i2c_probe,
	.priv_auto_alloc_size = sizeof(struct dw_i2c),
	.remove = designware_i2c_remove,
	.flags	= DM_FLAG_OS_PREPARE,
	.ops	= &designware_i2c_ops,
};

#endif /* CONFIG_DM_I2C */