xref: /openbmc/linux/drivers/i2c/algos/i2c-algo-pcf.c (revision c942fddf)

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * i2c-algo-pcf.c i2c driver algorithms for PCF8584 adapters
 *
 *   Copyright (C) 1995-1997 Simon G. Vogl
 *		   1998-2000 Hans Berglund
 *
 * With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and
 * Frodo Looijaard <frodol@dds.nl>, and also from Martin Bailey
 * <mbailey@littlefeet-inc.com>
 *
 * Partially rewriten by Oleg I. Vdovikin <vdovikin@jscc.ru> to handle multiple
 * messages, proper stop/repstart signaling during receive, added detect code
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-pcf.h>
#include "i2c-algo-pcf.h"


#define DEB2(x) if (i2c_debug >= 2) x
#define DEB3(x) if (i2c_debug >= 3) x /* print several statistical values */
#define DEBPROTO(x) if (i2c_debug >= 9) x;
	/* debug the protocol by showing transferred bits */
#define DEF_TIMEOUT 16

/*
 * module parameters:
 */
static int i2c_debug;

/* setting states on the bus with the right timing: */

#define set_pcf(adap, ctl, val) adap->setpcf(adap->data, ctl, val)
#define get_pcf(adap, ctl) adap->getpcf(adap->data, ctl)
#define get_own(adap) adap->getown(adap->data)
#define get_clock(adap) adap->getclock(adap->data)
#define i2c_outb(adap, val) adap->setpcf(adap->data, 0, val)
#define i2c_inb(adap) adap->getpcf(adap->data, 0)

/* other auxiliary functions */

static void i2c_start(struct i2c_algo_pcf_data *adap)
{
	DEBPROTO(printk(KERN_DEBUG "S "));
	set_pcf(adap, 1, I2C_PCF_START);
}

static void i2c_repstart(struct i2c_algo_pcf_data *adap)
{
	DEBPROTO(printk(" Sr "));
	set_pcf(adap, 1, I2C_PCF_REPSTART);
}

static void i2c_stop(struct i2c_algo_pcf_data *adap)
{
	DEBPROTO(printk("P\n"));
	set_pcf(adap, 1, I2C_PCF_STOP);
}

static void handle_lab(struct i2c_algo_pcf_data *adap, const int *status)
{
	DEB2(printk(KERN_INFO
		"i2c-algo-pcf.o: lost arbitration (CSR 0x%02x)\n",
		*status));
	/*
	 * Cleanup from LAB -- reset and enable ESO.
	 * This resets the PCF8584; since we've lost the bus, no
	 * further attempts should be made by callers to clean up
	 * (no i2c_stop() etc.)
	 */
	set_pcf(adap, 1, I2C_PCF_PIN);
	set_pcf(adap, 1, I2C_PCF_ESO);
	/*
	 * We pause for a time period sufficient for any running
	 * I2C transaction to complete -- the arbitration logic won't
	 * work properly until the next START is seen.
	 * It is assumed the bus driver or client has set a proper value.
	 *
	 * REVISIT: should probably use msleep instead of mdelay if we
	 * know we can sleep.
	 */
	if (adap->lab_mdelay)
		mdelay(adap->lab_mdelay);

	DEB2(printk(KERN_INFO
		"i2c-algo-pcf.o: reset LAB condition (CSR 0x%02x)\n",
		get_pcf(adap, 1)));
}

static int wait_for_bb(struct i2c_algo_pcf_data *adap)
{

	int timeout = DEF_TIMEOUT;
	int status;

	status = get_pcf(adap, 1);

	while (!(status & I2C_PCF_BB) && --timeout) {
		udelay(100); /* wait for 100 us */
		status = get_pcf(adap, 1);
	}

	if (timeout == 0) {
		printk(KERN_ERR "Timeout waiting for Bus Busy\n");
		return -ETIMEDOUT;
	}

	return 0;
}

static int wait_for_pin(struct i2c_algo_pcf_data *adap, int *status)
{

	int timeout = DEF_TIMEOUT;

	*status = get_pcf(adap, 1);

	while ((*status & I2C_PCF_PIN) && --timeout) {
		adap->waitforpin(adap->data);
		*status = get_pcf(adap, 1);
	}
	if (*status & I2C_PCF_LAB) {
		handle_lab(adap, status);
		return -EINTR;
	}

	if (timeout == 0)
		return -ETIMEDOUT;

	return 0;
}

/*
 * This should perform the 'PCF8584 initialization sequence' as described
 * in the Philips IC12 data book (1995, Aug 29).
 * There should be a 30 clock cycle wait after reset, I assume this
 * has been fulfilled.
 * There should be a delay at the end equal to the longest I2C message
 * to synchronize the BB-bit (in multimaster systems). How long is
 * this? I assume 1 second is always long enough.
 *
 * vdovikin: added detect code for PCF8584
 */
static int pcf_init_8584 (struct i2c_algo_pcf_data *adap)
{
	unsigned char temp;

	DEB3(printk(KERN_DEBUG "i2c-algo-pcf.o: PCF state 0x%02x\n",
				get_pcf(adap, 1)));

	/* S1=0x80: S0 selected, serial interface off */
	set_pcf(adap, 1, I2C_PCF_PIN);
	/*
	 * check to see S1 now used as R/W ctrl -
	 * PCF8584 does that when ESO is zero
	 */
	if (((temp = get_pcf(adap, 1)) & 0x7f) != (0)) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: PCF detection failed -- can't select S0 (0x%02x).\n", temp));
		return -ENXIO; /* definitely not PCF8584 */
	}

	/* load own address in S0, effective address is (own << 1) */
	i2c_outb(adap, get_own(adap));
	/* check it's really written */
	if ((temp = i2c_inb(adap)) != get_own(adap)) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: PCF detection failed -- can't set S0 (0x%02x).\n", temp));
		return -ENXIO;
	}

	/* S1=0xA0, next byte in S2 */
	set_pcf(adap, 1, I2C_PCF_PIN | I2C_PCF_ES1);
	/* check to see S2 now selected */
	if (((temp = get_pcf(adap, 1)) & 0x7f) != I2C_PCF_ES1) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: PCF detection failed -- can't select S2 (0x%02x).\n", temp));
		return -ENXIO;
	}

	/* load clock register S2 */
	i2c_outb(adap, get_clock(adap));
	/* check it's really written, the only 5 lowest bits does matter */
	if (((temp = i2c_inb(adap)) & 0x1f) != get_clock(adap)) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: PCF detection failed -- can't set S2 (0x%02x).\n", temp));
		return -ENXIO;
	}

	/* Enable serial interface, idle, S0 selected */
	set_pcf(adap, 1, I2C_PCF_IDLE);

	/* check to see PCF is really idled and we can access status register */
	if ((temp = get_pcf(adap, 1)) != (I2C_PCF_PIN | I2C_PCF_BB)) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: PCF detection failed -- can't select S1` (0x%02x).\n", temp));
		return -ENXIO;
	}

	printk(KERN_DEBUG "i2c-algo-pcf.o: detected and initialized PCF8584.\n");

	return 0;
}

static int pcf_sendbytes(struct i2c_adapter *i2c_adap, const char *buf,
			 int count, int last)
{
	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
	int wrcount, status, timeout;

	for (wrcount=0; wrcount<count; ++wrcount) {
		DEB2(dev_dbg(&i2c_adap->dev, "i2c_write: writing %2.2X\n",
				buf[wrcount] & 0xff));
		i2c_outb(adap, buf[wrcount]);
		timeout = wait_for_pin(adap, &status);
		if (timeout) {
			if (timeout == -EINTR)
				return -EINTR; /* arbitration lost */

			i2c_stop(adap);
			dev_err(&i2c_adap->dev, "i2c_write: error - timeout.\n");
			return -EREMOTEIO; /* got a better one ?? */
		}
		if (status & I2C_PCF_LRB) {
			i2c_stop(adap);
			dev_err(&i2c_adap->dev, "i2c_write: error - no ack.\n");
			return -EREMOTEIO; /* got a better one ?? */
		}
	}
	if (last)
		i2c_stop(adap);
	else
		i2c_repstart(adap);

	return wrcount;
}

static int pcf_readbytes(struct i2c_adapter *i2c_adap, char *buf,
			 int count, int last)
{
	int i, status;
	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
	int wfp;

	/* increment number of bytes to read by one -- read dummy byte */
	for (i = 0; i <= count; i++) {

		if ((wfp = wait_for_pin(adap, &status))) {
			if (wfp == -EINTR)
				return -EINTR; /* arbitration lost */

			i2c_stop(adap);
			dev_err(&i2c_adap->dev, "pcf_readbytes timed out.\n");
			return -1;
		}

		if ((status & I2C_PCF_LRB) && (i != count)) {
			i2c_stop(adap);
			dev_err(&i2c_adap->dev, "i2c_read: i2c_inb, No ack.\n");
			return -1;
		}

		if (i == count - 1) {
			set_pcf(adap, 1, I2C_PCF_ESO);
		} else if (i == count) {
			if (last)
				i2c_stop(adap);
			else
				i2c_repstart(adap);
		}

		if (i)
			buf[i - 1] = i2c_inb(adap);
		else
			i2c_inb(adap); /* dummy read */
	}

	return i - 1;
}


static int pcf_doAddress(struct i2c_algo_pcf_data *adap,
			 struct i2c_msg *msg)
{
	unsigned char addr = i2c_8bit_addr_from_msg(msg);

	if (msg->flags & I2C_M_REV_DIR_ADDR)
		addr ^= 1;
	i2c_outb(adap, addr);

	return 0;
}

static int pcf_xfer(struct i2c_adapter *i2c_adap,
		    struct i2c_msg *msgs,
		    int num)
{
	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
	struct i2c_msg *pmsg;
	int i;
	int ret=0, timeout, status;

	if (adap->xfer_begin)
		adap->xfer_begin(adap->data);

	/* Check for bus busy */
	timeout = wait_for_bb(adap);
	if (timeout) {
		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: "
			    "Timeout waiting for BB in pcf_xfer\n");)
		i = -EIO;
		goto out;
	}

	for (i = 0;ret >= 0 && i < num; i++) {
		pmsg = &msgs[i];

		DEB2(printk(KERN_DEBUG "i2c-algo-pcf.o: Doing %s %d bytes to 0x%02x - %d of %d messages\n",
		     pmsg->flags & I2C_M_RD ? "read" : "write",
		     pmsg->len, pmsg->addr, i + 1, num);)

		ret = pcf_doAddress(adap, pmsg);

		/* Send START */
		if (i == 0)
			i2c_start(adap);

		/* Wait for PIN (pending interrupt NOT) */
		timeout = wait_for_pin(adap, &status);
		if (timeout) {
			if (timeout == -EINTR) {
				/* arbitration lost */
				i = -EINTR;
				goto out;
			}
			i2c_stop(adap);
			DEB2(printk(KERN_ERR "i2c-algo-pcf.o: Timeout waiting "
				    "for PIN(1) in pcf_xfer\n");)
			i = -EREMOTEIO;
			goto out;
		}

		/* Check LRB (last rcvd bit - slave ack) */
		if (status & I2C_PCF_LRB) {
			i2c_stop(adap);
			DEB2(printk(KERN_ERR "i2c-algo-pcf.o: No LRB(1) in pcf_xfer\n");)
			i = -EREMOTEIO;
			goto out;
		}

		DEB3(printk(KERN_DEBUG "i2c-algo-pcf.o: Msg %d, addr=0x%x, flags=0x%x, len=%d\n",
			    i, msgs[i].addr, msgs[i].flags, msgs[i].len);)

		if (pmsg->flags & I2C_M_RD) {
			ret = pcf_readbytes(i2c_adap, pmsg->buf, pmsg->len,
					    (i + 1 == num));

			if (ret != pmsg->len) {
				DEB2(printk(KERN_DEBUG "i2c-algo-pcf.o: fail: "
					    "only read %d bytes.\n",ret));
			} else {
				DEB2(printk(KERN_DEBUG "i2c-algo-pcf.o: read %d bytes.\n",ret));
			}
		} else {
			ret = pcf_sendbytes(i2c_adap, pmsg->buf, pmsg->len,
					    (i + 1 == num));

			if (ret != pmsg->len) {
				DEB2(printk(KERN_DEBUG "i2c-algo-pcf.o: fail: "
					    "only wrote %d bytes.\n",ret));
			} else {
				DEB2(printk(KERN_DEBUG "i2c-algo-pcf.o: wrote %d bytes.\n",ret));
			}
		}
	}

out:
	if (adap->xfer_end)
		adap->xfer_end(adap->data);
	return i;
}

static u32 pcf_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
	       I2C_FUNC_PROTOCOL_MANGLING;
}

/* exported algorithm data: */
static const struct i2c_algorithm pcf_algo = {
	.master_xfer	= pcf_xfer,
	.functionality	= pcf_func,
};

/*
 * registering functions to load algorithms at runtime
 */
int i2c_pcf_add_bus(struct i2c_adapter *adap)
{
	struct i2c_algo_pcf_data *pcf_adap = adap->algo_data;
	int rval;

	DEB2(dev_dbg(&adap->dev, "hw routines registered.\n"));

	/* register new adapter to i2c module... */
	adap->algo = &pcf_algo;

	if ((rval = pcf_init_8584(pcf_adap)))
		return rval;

	rval = i2c_add_adapter(adap);

	return rval;
}
EXPORT_SYMBOL(i2c_pcf_add_bus);

MODULE_AUTHOR("Hans Berglund <hb@spacetec.no>");
MODULE_DESCRIPTION("I2C-Bus PCF8584 algorithm");
MODULE_LICENSE("GPL");

module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(i2c_debug,
	"debug level - 0 off; 1 normal; 2,3 more verbose; 9 pcf-protocol");