drivers/i2c/busses/i2c-mlxcpld.c

// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/*
 * Mellanox i2c driver
 *
 * Copyright (C) 2016-2020 Mellanox Technologies
 */

#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_data/mlxreg.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>

/* General defines */
#define MLXPLAT_CPLD_LPC_I2C_BASE_ADDR	0x2000
#define MLXCPLD_I2C_DEVICE_NAME		"i2c_mlxcpld"
#define MLXCPLD_I2C_VALID_FLAG		(I2C_M_RECV_LEN | I2C_M_RD)
#define MLXCPLD_I2C_BUS_NUM		1
#define MLXCPLD_I2C_DATA_REG_SZ		36
#define MLXCPLD_I2C_DATA_SZ_BIT		BIT(5)
#define MLXCPLD_I2C_DATA_SZ_MASK	GENMASK(6, 5)
#define MLXCPLD_I2C_SMBUS_BLK_BIT	BIT(7)
#define MLXCPLD_I2C_MAX_ADDR_LEN	4
#define MLXCPLD_I2C_RETR_NUM		2
#define MLXCPLD_I2C_XFER_TO		500000 /* usec */
#define MLXCPLD_I2C_POLL_TIME		400   /* usec */

/* LPC I2C registers */
#define MLXCPLD_LPCI2C_CPBLTY_REG	0x0
#define MLXCPLD_LPCI2C_CTRL_REG		0x1
#define MLXCPLD_LPCI2C_HALF_CYC_REG	0x4
#define MLXCPLD_LPCI2C_I2C_HOLD_REG	0x5
#define MLXCPLD_LPCI2C_CMD_REG		0x6
#define MLXCPLD_LPCI2C_NUM_DAT_REG	0x7
#define MLXCPLD_LPCI2C_NUM_ADDR_REG	0x8
#define MLXCPLD_LPCI2C_STATUS_REG	0x9
#define MLXCPLD_LPCI2C_DATA_REG		0xa

/* LPC I2C masks and parametres */
#define MLXCPLD_LPCI2C_RST_SEL_MASK	0x1
#define MLXCPLD_LPCI2C_TRANS_END	0x1
#define MLXCPLD_LPCI2C_STATUS_NACK	0x10
#define MLXCPLD_LPCI2C_NO_IND		0
#define MLXCPLD_LPCI2C_ACK_IND		1
#define MLXCPLD_LPCI2C_NACK_IND		2

#define MLXCPLD_I2C_FREQ_1000KHZ_SET	0x04
#define MLXCPLD_I2C_FREQ_400KHZ_SET	0x0c
#define MLXCPLD_I2C_FREQ_100KHZ_SET	0x42

enum mlxcpld_i2c_frequency {
	MLXCPLD_I2C_FREQ_1000KHZ = 1,
	MLXCPLD_I2C_FREQ_400KHZ = 2,
	MLXCPLD_I2C_FREQ_100KHZ = 3,
};

struct  mlxcpld_i2c_curr_xfer {
	u8 cmd;
	u8 addr_width;
	u8 data_len;
	u8 msg_num;
	struct i2c_msg *msg;
};

struct mlxcpld_i2c_priv {
	struct i2c_adapter adap;
	u32 base_addr;
	struct mutex lock;
	struct  mlxcpld_i2c_curr_xfer xfer;
	struct device *dev;
	bool smbus_block;
};

static void mlxcpld_i2c_lpc_write_buf(u8 *data, u8 len, u32 addr)
{
	int i;

	for (i = 0; i < len - len % 4; i += 4)
		outl(*(u32 *)(data + i), addr + i);
	for (; i < len; ++i)
		outb(*(data + i), addr + i);
}

static void mlxcpld_i2c_lpc_read_buf(u8 *data, u8 len, u32 addr)
{
	int i;

	for (i = 0; i < len - len % 4; i += 4)
		*(u32 *)(data + i) = inl(addr + i);
	for (; i < len; ++i)
		*(data + i) = inb(addr + i);
}

static void mlxcpld_i2c_read_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
				  u8 *data, u8 datalen)
{
	u32 addr = priv->base_addr + offs;

	switch (datalen) {
	case 1:
		*(data) = inb(addr);
		break;
	case 2:
		*((u16 *)data) = inw(addr);
		break;
	case 3:
		*((u16 *)data) = inw(addr);
		*(data + 2) = inb(addr + 2);
		break;
	case 4:
		*((u32 *)data) = inl(addr);
		break;
	default:
		mlxcpld_i2c_lpc_read_buf(data, datalen, addr);
		break;
	}
}

static void mlxcpld_i2c_write_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
				   u8 *data, u8 datalen)
{
	u32 addr = priv->base_addr + offs;

	switch (datalen) {
	case 1:
		outb(*(data), addr);
		break;
	case 2:
		outw(*((u16 *)data), addr);
		break;
	case 3:
		outw(*((u16 *)data), addr);
		outb(*(data + 2), addr + 2);
		break;
	case 4:
		outl(*((u32 *)data), addr);
		break;
	default:
		mlxcpld_i2c_lpc_write_buf(data, datalen, addr);
		break;
	}
}

/*
 * Check validity of received i2c messages parameters.
 * Returns 0 if OK, other - in case of invalid parameters.
 */
static int mlxcpld_i2c_check_msg_params(struct mlxcpld_i2c_priv *priv,
					struct i2c_msg *msgs, int num)
{
	int i;

	if (!num) {
		dev_err(priv->dev, "Incorrect 0 num of messages\n");
		return -EINVAL;
	}

	if (unlikely(msgs[0].addr > 0x7f)) {
		dev_err(priv->dev, "Invalid address 0x%03x\n",
			msgs[0].addr);
		return -EINVAL;
	}

	for (i = 0; i < num; ++i) {
		if (unlikely(!msgs[i].buf)) {
			dev_err(priv->dev, "Invalid buf in msg[%d]\n",
				i);
			return -EINVAL;
		}
		if (unlikely(msgs[0].addr != msgs[i].addr)) {
			dev_err(priv->dev, "Invalid addr in msg[%d]\n",
				i);
			return -EINVAL;
		}
	}

	return 0;
}

/*
 * Check if transfer is completed and status of operation.
 * Returns 0 - transfer completed (both ACK or NACK),
 * negative - transfer isn't finished.
 */
static int mlxcpld_i2c_check_status(struct mlxcpld_i2c_priv *priv, int *status)
{
	u8 val;

	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);

	if (val & MLXCPLD_LPCI2C_TRANS_END) {
		if (val & MLXCPLD_LPCI2C_STATUS_NACK)
			/*
			 * The slave is unable to accept the data. No such
			 * slave, command not understood, or unable to accept
			 * any more data.
			 */
			*status = MLXCPLD_LPCI2C_NACK_IND;
		else
			*status = MLXCPLD_LPCI2C_ACK_IND;
		return 0;
	}
	*status = MLXCPLD_LPCI2C_NO_IND;

	return -EIO;
}

static void mlxcpld_i2c_set_transf_data(struct mlxcpld_i2c_priv *priv,
					struct i2c_msg *msgs, int num,
					u8 comm_len)
{
	priv->xfer.msg = msgs;
	priv->xfer.msg_num = num;

	/*
	 * All upper layers currently are never use transfer with more than
	 * 2 messages. Actually, it's also not so relevant in Mellanox systems
	 * because of HW limitation. Max size of transfer is not more than 32
	 * or 68 bytes in the current x86 LPCI2C bridge.
	 */
	priv->xfer.cmd = msgs[num - 1].flags & I2C_M_RD;

	if (priv->xfer.cmd == I2C_M_RD && comm_len != msgs[0].len) {
		priv->xfer.addr_width = msgs[0].len;
		priv->xfer.data_len = comm_len - priv->xfer.addr_width;
	} else {
		priv->xfer.addr_width = 0;
		priv->xfer.data_len = comm_len;
	}
}

/* Reset CPLD LPCI2C block */
static void mlxcpld_i2c_reset(struct mlxcpld_i2c_priv *priv)
{
	u8 val;

	mutex_lock(&priv->lock);

	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
	val &= ~MLXCPLD_LPCI2C_RST_SEL_MASK;
	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);

	mutex_unlock(&priv->lock);
}

/* Make sure the CPLD is ready to start transmitting. */
static int mlxcpld_i2c_check_busy(struct mlxcpld_i2c_priv *priv)
{
	u8 val;

	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);

	if (val & MLXCPLD_LPCI2C_TRANS_END)
		return 0;

	return -EIO;
}

static int mlxcpld_i2c_wait_for_free(struct mlxcpld_i2c_priv *priv)
{
	int timeout = 0;

	do {
		if (!mlxcpld_i2c_check_busy(priv))
			break;
		usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
		timeout += MLXCPLD_I2C_POLL_TIME;
	} while (timeout <= MLXCPLD_I2C_XFER_TO);

	if (timeout > MLXCPLD_I2C_XFER_TO)
		return -ETIMEDOUT;

	return 0;
}

/*
 * Wait for master transfer to complete.
 * It puts current process to sleep until we get interrupt or timeout expires.
 * Returns the number of transferred or read bytes or error (<0).
 */
static int mlxcpld_i2c_wait_for_tc(struct mlxcpld_i2c_priv *priv)
{
	int status, i, timeout = 0;
	u8 datalen, val;

	do {
		usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
		if (!mlxcpld_i2c_check_status(priv, &status))
			break;
		timeout += MLXCPLD_I2C_POLL_TIME;
	} while (status == 0 && timeout < MLXCPLD_I2C_XFER_TO);

	switch (status) {
	case MLXCPLD_LPCI2C_NO_IND:
		return -ETIMEDOUT;

	case MLXCPLD_LPCI2C_ACK_IND:
		if (priv->xfer.cmd != I2C_M_RD)
			return (priv->xfer.addr_width + priv->xfer.data_len);

		if (priv->xfer.msg_num == 1)
			i = 0;
		else
			i = 1;

		if (!priv->xfer.msg[i].buf)
			return -EINVAL;

		/*
		 * Actual read data len will be always the same as
		 * requested len. 0xff (line pull-up) will be returned
		 * if slave has no data to return. Thus don't read
		 * MLXCPLD_LPCI2C_NUM_DAT_REG reg from CPLD.  Only in case of
		 * SMBus block read transaction data len can be different,
		 * check this case.
		 */
		mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_NUM_ADDR_REG, &val,
				      1);
		if (priv->smbus_block && (val & MLXCPLD_I2C_SMBUS_BLK_BIT)) {
			mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_NUM_DAT_REG,
					      &datalen, 1);
			if (unlikely(datalen > I2C_SMBUS_BLOCK_MAX)) {
				dev_err(priv->dev, "Incorrect smbus block read message len\n");
				return -EPROTO;
			}
		} else {
			datalen = priv->xfer.data_len;
		}

		mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_DATA_REG,
				      priv->xfer.msg[i].buf, datalen);

		return datalen;

	case MLXCPLD_LPCI2C_NACK_IND:
		return -ENXIO;

	default:
		return -EINVAL;
	}
}

static void mlxcpld_i2c_xfer_msg(struct mlxcpld_i2c_priv *priv)
{
	int i, len = 0;
	u8 cmd, val;

	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_DAT_REG,
			       &priv->xfer.data_len, 1);

	val = priv->xfer.addr_width;
	/* Notify HW about SMBus block read transaction */
	if (priv->smbus_block && priv->xfer.msg_num >= 2 &&
	    priv->xfer.msg[1].len == 1 &&
	    (priv->xfer.msg[1].flags & I2C_M_RECV_LEN) &&
	    (priv->xfer.msg[1].flags & I2C_M_RD))
		val |= MLXCPLD_I2C_SMBUS_BLK_BIT;

	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_ADDR_REG, &val, 1);

	for (i = 0; i < priv->xfer.msg_num; i++) {
		if ((priv->xfer.msg[i].flags & I2C_M_RD) != I2C_M_RD) {
			/* Don't write to CPLD buffer in read transaction */
			mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_DATA_REG +
					       len, priv->xfer.msg[i].buf,
					       priv->xfer.msg[i].len);
			len += priv->xfer.msg[i].len;
		}
	}

	/*
	 * Set target slave address with command for master transfer.
	 * It should be latest executed function before CPLD transaction.
	 */
	cmd = (priv->xfer.msg[0].addr << 1) | priv->xfer.cmd;
	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CMD_REG, &cmd, 1);
}

/*
 * Generic lpc-i2c transfer.
 * Returns the number of processed messages or error (<0).
 */
static int mlxcpld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
			    int num)
{
	struct mlxcpld_i2c_priv *priv = i2c_get_adapdata(adap);
	u8 comm_len = 0;
	int i, err;

	err = mlxcpld_i2c_check_msg_params(priv, msgs, num);
	if (err) {
		dev_err(priv->dev, "Incorrect message\n");
		return err;
	}

	for (i = 0; i < num; ++i)
		comm_len += msgs[i].len;

	/* Check bus state */
	if (mlxcpld_i2c_wait_for_free(priv)) {
		dev_err(priv->dev, "LPCI2C bridge is busy\n");

		/*
		 * Usually it means something serious has happened.
		 * We can not have unfinished previous transfer
		 * so it doesn't make any sense to try to stop it.
		 * Probably we were not able to recover from the
		 * previous error.
		 * The only reasonable thing - is soft reset.
		 */
		mlxcpld_i2c_reset(priv);
		if (mlxcpld_i2c_check_busy(priv)) {
			dev_err(priv->dev, "LPCI2C bridge is busy after reset\n");
			return -EIO;
		}
	}

	mlxcpld_i2c_set_transf_data(priv, msgs, num, comm_len);

	mutex_lock(&priv->lock);

	/* Do real transfer. Can't fail */
	mlxcpld_i2c_xfer_msg(priv);

	/* Wait for transaction complete */
	err = mlxcpld_i2c_wait_for_tc(priv);

	mutex_unlock(&priv->lock);

	return err < 0 ? err : num;
}

static u32 mlxcpld_i2c_func(struct i2c_adapter *adap)
{
	struct mlxcpld_i2c_priv *priv = i2c_get_adapdata(adap);

	if (priv->smbus_block)
		return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
			I2C_FUNC_SMBUS_I2C_BLOCK | I2C_FUNC_SMBUS_BLOCK_DATA;
	else
		return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
			I2C_FUNC_SMBUS_I2C_BLOCK;
}

static const struct i2c_algorithm mlxcpld_i2c_algo = {
	.master_xfer	= mlxcpld_i2c_xfer,
	.functionality	= mlxcpld_i2c_func
};

static const struct i2c_adapter_quirks mlxcpld_i2c_quirks = {
	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
	.max_read_len = MLXCPLD_I2C_DATA_REG_SZ - MLXCPLD_I2C_MAX_ADDR_LEN,
	.max_write_len = MLXCPLD_I2C_DATA_REG_SZ,
	.max_comb_1st_msg_len = 4,
};

static const struct i2c_adapter_quirks mlxcpld_i2c_quirks_ext = {
	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
	.max_read_len = MLXCPLD_I2C_DATA_REG_SZ * 2 - MLXCPLD_I2C_MAX_ADDR_LEN,
	.max_write_len = MLXCPLD_I2C_DATA_REG_SZ * 2,
	.max_comb_1st_msg_len = 4,
};

static struct i2c_adapter mlxcpld_i2c_adapter = {
	.owner          = THIS_MODULE,
	.name           = "i2c-mlxcpld",
	.class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
	.algo           = &mlxcpld_i2c_algo,
	.quirks		= &mlxcpld_i2c_quirks,
	.retries	= MLXCPLD_I2C_RETR_NUM,
	.nr		= MLXCPLD_I2C_BUS_NUM,
};

static int
mlxcpld_i2c_set_frequency(struct mlxcpld_i2c_priv *priv,
			  struct mlxreg_core_hotplug_platform_data *pdata)
{
	struct mlxreg_core_item *item = pdata->items;
	struct mlxreg_core_data *data;
	u32 regval;
	u8 freq;
	int err;

	if (!item)
		return 0;

	/* Read frequency setting. */
	data = item->data;
	err = regmap_read(pdata->regmap, data->reg, &regval);
	if (err)
		return err;

	/* Set frequency only if it is not 100KHz, which is default. */
	switch ((regval & data->mask) >> data->bit) {
	case MLXCPLD_I2C_FREQ_1000KHZ:
		freq = MLXCPLD_I2C_FREQ_1000KHZ_SET;
		break;
	case MLXCPLD_I2C_FREQ_400KHZ:
		freq = MLXCPLD_I2C_FREQ_400KHZ_SET;
		break;
	default:
		return 0;
	}

	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_HALF_CYC_REG, &freq, 1);

	return 0;
}

static int mlxcpld_i2c_probe(struct platform_device *pdev)
{
	struct mlxreg_core_hotplug_platform_data *pdata;
	struct mlxcpld_i2c_priv *priv;
	int err;
	u8 val;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	mutex_init(&priv->lock);
	platform_set_drvdata(pdev, priv);

	priv->dev = &pdev->dev;
	priv->base_addr = MLXPLAT_CPLD_LPC_I2C_BASE_ADDR;

	/* Set I2C bus frequency if platform data provides this info. */
	pdata = dev_get_platdata(&pdev->dev);
	if (pdata) {
		err = mlxcpld_i2c_set_frequency(priv, pdata);
		if (err)
			goto mlxcpld_i2_probe_failed;
	}

	/* Register with i2c layer */
	mlxcpld_i2c_adapter.timeout = usecs_to_jiffies(MLXCPLD_I2C_XFER_TO);
	/* Read capability register */
	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_CPBLTY_REG, &val, 1);
	/* Check support for extended transaction length */
	if ((val & MLXCPLD_I2C_DATA_SZ_MASK) == MLXCPLD_I2C_DATA_SZ_BIT)
		mlxcpld_i2c_adapter.quirks = &mlxcpld_i2c_quirks_ext;
	/* Check support for smbus block transaction */
	if (val & MLXCPLD_I2C_SMBUS_BLK_BIT)
		priv->smbus_block = true;
	if (pdev->id >= -1)
		mlxcpld_i2c_adapter.nr = pdev->id;
	priv->adap = mlxcpld_i2c_adapter;
	priv->adap.dev.parent = &pdev->dev;
	i2c_set_adapdata(&priv->adap, priv);

	err = i2c_add_numbered_adapter(&priv->adap);
	if (err)
		goto mlxcpld_i2_probe_failed;

	return 0;

mlxcpld_i2_probe_failed:
	mutex_destroy(&priv->lock);
	return err;
}

static int mlxcpld_i2c_remove(struct platform_device *pdev)
{
	struct mlxcpld_i2c_priv *priv = platform_get_drvdata(pdev);

	i2c_del_adapter(&priv->adap);
	mutex_destroy(&priv->lock);

	return 0;
}

static struct platform_driver mlxcpld_i2c_driver = {
	.probe		= mlxcpld_i2c_probe,
	.remove		= mlxcpld_i2c_remove,
	.driver = {
		.name = MLXCPLD_I2C_DEVICE_NAME,
	},
};

module_platform_driver(mlxcpld_i2c_driver);

MODULE_AUTHOR("Michael Shych <michaels@mellanox.com>");
MODULE_DESCRIPTION("Mellanox I2C-CPLD controller driver");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("platform:i2c-mlxcpld");