xref: /drivers/w1/w1_io.c

/*
 *	w1_io.c
 *
 * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <asm/io.h>

#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/module.h>

#include "w1.h"
#include "w1_log.h"

static int w1_delay_parm = 1;
module_param_named(delay_coef, w1_delay_parm, int, 0);

static u8 w1_crc8_table[] = {
	0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
	157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
	35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
	190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
	70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
	219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
	101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
	248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
	140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
	17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
	175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
	50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
	202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
	87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
	233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
	116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
};

static void w1_delay(unsigned long tm)
{
	udelay(tm * w1_delay_parm);
}

static void w1_write_bit(struct w1_master *dev, int bit);
static u8 w1_read_bit(struct w1_master *dev);

/**
 * Generates a write-0 or write-1 cycle and samples the level.
 */
static u8 w1_touch_bit(struct w1_master *dev, int bit)
{
	if (dev->bus_master->touch_bit)
		return dev->bus_master->touch_bit(dev->bus_master->data, bit);
	else if (bit)
		return w1_read_bit(dev);
	else {
		w1_write_bit(dev, 0);
		return 0;
	}
}

/**
 * Generates a write-0 or write-1 cycle.
 * Only call if dev->bus_master->touch_bit is NULL
 */
static void w1_write_bit(struct w1_master *dev, int bit)
{
	if (bit) {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		w1_delay(6);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(64);
	} else {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		w1_delay(60);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(10);
	}
}

/**
 * Pre-write operation, currently only supporting strong pullups.
 * Program the hardware for a strong pullup, if one has been requested and
 * the hardware supports it.
 *
 * @param dev     the master device
 */
static void w1_pre_write(struct w1_master *dev)
{
	if (dev->pullup_duration &&
		dev->enable_pullup && dev->bus_master->set_pullup) {
		dev->bus_master->set_pullup(dev->bus_master->data,
			dev->pullup_duration);
	}
}

/**
 * Post-write operation, currently only supporting strong pullups.
 * If a strong pullup was requested, clear it if the hardware supports
 * them, or execute the delay otherwise, in either case clear the request.
 *
 * @param dev     the master device
 */
static void w1_post_write(struct w1_master *dev)
{
	if (dev->pullup_duration) {
		if (dev->enable_pullup && dev->bus_master->set_pullup)
			dev->bus_master->set_pullup(dev->bus_master->data, 0);
		else
			msleep(dev->pullup_duration);
		dev->pullup_duration = 0;
	}
}

/**
 * Writes 8 bits.
 *
 * @param dev     the master device
 * @param byte    the byte to write
 */
void w1_write_8(struct w1_master *dev, u8 byte)
{
	int i;

	if (dev->bus_master->write_byte) {
		w1_pre_write(dev);
		dev->bus_master->write_byte(dev->bus_master->data, byte);
	}
	else
		for (i = 0; i < 8; ++i) {
			if (i == 7)
				w1_pre_write(dev);
			w1_touch_bit(dev, (byte >> i) & 0x1);
		}
	w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_8);


/**
 * Generates a write-1 cycle and samples the level.
 * Only call if dev->bus_master->touch_bit is NULL
 */
static u8 w1_read_bit(struct w1_master *dev)
{
	int result;
	unsigned long flags;

	/* sample timing is critical here */
	local_irq_save(flags);
	dev->bus_master->write_bit(dev->bus_master->data, 0);
	w1_delay(6);
	dev->bus_master->write_bit(dev->bus_master->data, 1);
	w1_delay(9);

	result = dev->bus_master->read_bit(dev->bus_master->data);
	local_irq_restore(flags);

	w1_delay(55);

	return result & 0x1;
}

/**
 * Does a triplet - used for searching ROM addresses.
 * Return bits:
 *  bit 0 = id_bit
 *  bit 1 = comp_bit
 *  bit 2 = dir_taken
 * If both bits 0 & 1 are set, the search should be restarted.
 *
 * @param dev     the master device
 * @param bdir    the bit to write if both id_bit and comp_bit are 0
 * @return        bit fields - see above
 */
u8 w1_triplet(struct w1_master *dev, int bdir)
{
	if (dev->bus_master->triplet)
		return dev->bus_master->triplet(dev->bus_master->data, bdir);
	else {
		u8 id_bit   = w1_touch_bit(dev, 1);
		u8 comp_bit = w1_touch_bit(dev, 1);
		u8 retval;

		if (id_bit && comp_bit)
			return 0x03;  /* error */

		if (!id_bit && !comp_bit) {
			/* Both bits are valid, take the direction given */
			retval = bdir ? 0x04 : 0;
		} else {
			/* Only one bit is valid, take that direction */
			bdir = id_bit;
			retval = id_bit ? 0x05 : 0x02;
		}

		if (dev->bus_master->touch_bit)
			w1_touch_bit(dev, bdir);
		else
			w1_write_bit(dev, bdir);
		return retval;
	}
}

/**
 * Reads 8 bits.
 *
 * @param dev     the master device
 * @return        the byte read
 */
u8 w1_read_8(struct w1_master *dev)
{
	int i;
	u8 res = 0;

	if (dev->bus_master->read_byte)
		res = dev->bus_master->read_byte(dev->bus_master->data);
	else
		for (i = 0; i < 8; ++i)
			res |= (w1_touch_bit(dev,1) << i);

	return res;
}
EXPORT_SYMBOL_GPL(w1_read_8);

/**
 * Writes a series of bytes.
 *
 * @param dev     the master device
 * @param buf     pointer to the data to write
 * @param len     the number of bytes to write
 */
void w1_write_block(struct w1_master *dev, const u8 *buf, int len)
{
	int i;

	if (dev->bus_master->write_block) {
		w1_pre_write(dev);
		dev->bus_master->write_block(dev->bus_master->data, buf, len);
	}
	else
		for (i = 0; i < len; ++i)
			w1_write_8(dev, buf[i]); /* calls w1_pre_write */
	w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_block);

/**
 * Touches a series of bytes.
 *
 * @param dev     the master device
 * @param buf     pointer to the data to write
 * @param len     the number of bytes to write
 */
void w1_touch_block(struct w1_master *dev, u8 *buf, int len)
{
	int i, j;
	u8 tmp;

	for (i = 0; i < len; ++i) {
		tmp = 0;
		for (j = 0; j < 8; ++j) {
			if (j == 7)
				w1_pre_write(dev);
			tmp |= w1_touch_bit(dev, (buf[i] >> j) & 0x1) << j;
		}

		buf[i] = tmp;
	}
}
EXPORT_SYMBOL_GPL(w1_touch_block);

/**
 * Reads a series of bytes.
 *
 * @param dev     the master device
 * @param buf     pointer to the buffer to fill
 * @param len     the number of bytes to read
 * @return        the number of bytes read
 */
u8 w1_read_block(struct w1_master *dev, u8 *buf, int len)
{
	int i;
	u8 ret;

	if (dev->bus_master->read_block)
		ret = dev->bus_master->read_block(dev->bus_master->data, buf, len);
	else {
		for (i = 0; i < len; ++i)
			buf[i] = w1_read_8(dev);
		ret = len;
	}

	return ret;
}
EXPORT_SYMBOL_GPL(w1_read_block);

/**
 * Issues a reset bus sequence.
 *
 * @param  dev The bus master pointer
 * @return     0=Device present, 1=No device present or error
 */
int w1_reset_bus(struct w1_master *dev)
{
	int result;

	if (dev->bus_master->reset_bus)
		result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
	else {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		/* minimum 480, max ? us
		 * be nice and sleep, except 18b20 spec lists 960us maximum,
		 * so until we can sleep with microsecond accuracy, spin.
		 * Feel free to come up with some other way to give up the
		 * cpu for such a short amount of time AND get it back in
		 * the maximum amount of time.
		 */
		w1_delay(480);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(70);

		result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
		/* minmum 70 (above) + 410 = 480 us
		 * There aren't any timing requirements between a reset and
		 * the following transactions.  Sleeping is safe here.
		 */
		/* w1_delay(410); min required time */
		msleep(1);
	}

	return result;
}
EXPORT_SYMBOL_GPL(w1_reset_bus);

u8 w1_calc_crc8(u8 * data, int len)
{
	u8 crc = 0;

	while (len--)
		crc = w1_crc8_table[crc ^ *data++];

	return crc;
}
EXPORT_SYMBOL_GPL(w1_calc_crc8);

void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
{
	dev->attempts++;
	if (dev->bus_master->search)
		dev->bus_master->search(dev->bus_master->data, dev,
			search_type, cb);
	else
		w1_search(dev, search_type, cb);
}

/**
 * Resets the bus and then selects the slave by sending either a skip rom
 * or a rom match.
 * The w1 master lock must be held.
 *
 * @param sl	the slave to select
 * @return 	0=success, anything else=error
 */
int w1_reset_select_slave(struct w1_slave *sl)
{
	if (w1_reset_bus(sl->master))
		return -1;

	if (sl->master->slave_count == 1)
		w1_write_8(sl->master, W1_SKIP_ROM);
	else {
		u8 match[9] = {W1_MATCH_ROM, };
		u64 rn = le64_to_cpu(*((u64*)&sl->reg_num));

		memcpy(&match[1], &rn, 8);
		w1_write_block(sl->master, match, 9);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(w1_reset_select_slave);

/**
 * When the workflow with a slave amongst many requires several
 * successive commands a reset between each, this function is similar
 * to doing a reset then a match ROM for the last matched ROM. The
 * advantage being that the matched ROM step is skipped in favor of the
 * resume command. The slave must support the command of course.
 *
 * If the bus has only one slave, traditionnaly the match ROM is skipped
 * and a "SKIP ROM" is done for efficiency. On multi-slave busses, this
 * doesn't work of course, but the resume command is the next best thing.
 *
 * The w1 master lock must be held.
 *
 * @param dev     the master device
 */
int w1_reset_resume_command(struct w1_master *dev)
{
	if (w1_reset_bus(dev))
		return -1;

	/* This will make only the last matched slave perform a skip ROM. */
	w1_write_8(dev, W1_RESUME_CMD);
	return 0;
}
EXPORT_SYMBOL_GPL(w1_reset_resume_command);

/**
 * Put out a strong pull-up of the specified duration after the next write
 * operation.  Not all hardware supports strong pullups.  Hardware that
 * doesn't support strong pullups will sleep for the given time after the
 * write operation without a strong pullup.  This is a one shot request for
 * the next write, specifying zero will clear a previous request.
 * The w1 master lock must be held.
 *
 * @param delay	time in milliseconds
 * @return	0=success, anything else=error
 */
void w1_next_pullup(struct w1_master *dev, int delay)
{
	dev->pullup_duration = delay;
}
EXPORT_SYMBOL_GPL(w1_next_pullup);