1/*
2 * i2c-algo-sgi.c: i2c driver algorithm used by the VINO (SGI Indy) and
3 * MACE (SGI O2) chips.
4 *
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License version 2 as published by the Free Software Foundation.
7 *
8 * Copyright (C) 2003 Ladislav Michl <ladis@linux-mips.org>
9 */
10
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/errno.h>
15#include <linux/delay.h>
16
17#include <linux/i2c.h>
18#include <linux/i2c-algo-sgi.h>
19
20
21#define SGI_I2C_FORCE_IDLE	(0 << 0)
22#define SGI_I2C_NOT_IDLE	(1 << 0)
23#define SGI_I2C_WRITE		(0 << 1)
24#define SGI_I2C_READ		(1 << 1)
25#define SGI_I2C_RELEASE_BUS	(0 << 2)
26#define SGI_I2C_HOLD_BUS	(1 << 2)
27#define SGI_I2C_XFER_DONE	(0 << 4)
28#define SGI_I2C_XFER_BUSY	(1 << 4)
29#define SGI_I2C_ACK		(0 << 5)
30#define SGI_I2C_NACK		(1 << 5)
31#define SGI_I2C_BUS_OK		(0 << 7)
32#define SGI_I2C_BUS_ERR		(1 << 7)
33
34#define get_control()		adap->getctrl(adap->data)
35#define set_control(val)	adap->setctrl(adap->data, val)
36#define read_data()		adap->rdata(adap->data)
37#define write_data(val)		adap->wdata(adap->data, val)
38
39
40static int wait_xfer_done(struct i2c_algo_sgi_data *adap)
41{
42	int i;
43
44	for (i = 0; i < adap->xfer_timeout; i++) {
45		if ((get_control() & SGI_I2C_XFER_BUSY) == 0)
46			return 0;
47		udelay(1);
48	}
49
50	return -ETIMEDOUT;
51}
52
53static int wait_ack(struct i2c_algo_sgi_data *adap)
54{
55	int i;
56
57	if (wait_xfer_done(adap))
58		return -ETIMEDOUT;
59	for (i = 0; i < adap->ack_timeout; i++) {
60		if ((get_control() & SGI_I2C_NACK) == 0)
61			return 0;
62		udelay(1);
63	}
64
65	return -ETIMEDOUT;
66}
67
68static int force_idle(struct i2c_algo_sgi_data *adap)
69{
70	int i;
71
72	set_control(SGI_I2C_FORCE_IDLE);
73	for (i = 0; i < adap->xfer_timeout; i++) {
74		if ((get_control() & SGI_I2C_NOT_IDLE) == 0)
75			goto out;
76		udelay(1);
77	}
78	return -ETIMEDOUT;
79out:
80	if (get_control() & SGI_I2C_BUS_ERR)
81		return -EIO;
82	return 0;
83}
84
85static int do_address(struct i2c_algo_sgi_data *adap, unsigned int addr,
86		      int rd)
87{
88	if (rd)
89		set_control(SGI_I2C_NOT_IDLE);
90	/* Check if bus is idle, eventually force it to do so */
91	if (get_control() & SGI_I2C_NOT_IDLE)
92		if (force_idle(adap))
93	                return -EIO;
94	/* Write out the i2c chip address and specify operation */
95	set_control(SGI_I2C_HOLD_BUS | SGI_I2C_WRITE | SGI_I2C_NOT_IDLE);
96	if (rd)
97		addr |= 1;
98	write_data(addr);
99	if (wait_ack(adap))
100		return -EIO;
101	return 0;
102}
103
104static int i2c_read(struct i2c_algo_sgi_data *adap, unsigned char *buf,
105		    unsigned int len)
106{
107	int i;
108
109	set_control(SGI_I2C_HOLD_BUS | SGI_I2C_READ | SGI_I2C_NOT_IDLE);
110	for (i = 0; i < len; i++) {
111		if (wait_xfer_done(adap))
112			return -EIO;
113		buf[i] = read_data();
114	}
115	set_control(SGI_I2C_RELEASE_BUS | SGI_I2C_FORCE_IDLE);
116
117	return 0;
118
119}
120
121static int i2c_write(struct i2c_algo_sgi_data *adap, unsigned char *buf,
122		     unsigned int len)
123{
124	int i;
125
126	/* We are already in write state */
127	for (i = 0; i < len; i++) {
128		write_data(buf[i]);
129		if (wait_ack(adap))
130			return -EIO;
131	}
132	return 0;
133}
134
135static int sgi_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg *msgs,
136		    int num)
137{
138	struct i2c_algo_sgi_data *adap = i2c_adap->algo_data;
139	struct i2c_msg *p;
140	int i, err = 0;
141
142	for (i = 0; !err && i < num; i++) {
143		p = &msgs[i];
144		err = do_address(adap, p->addr, p->flags & I2C_M_RD);
145		if (err || !p->len)
146			continue;
147		if (p->flags & I2C_M_RD)
148			err = i2c_read(adap, p->buf, p->len);
149		else
150			err = i2c_write(adap, p->buf, p->len);
151	}
152
153	return (err < 0) ? err : i;
154}
155
156static u32 sgi_func(struct i2c_adapter *adap)
157{
158	return I2C_FUNC_SMBUS_EMUL;
159}
160
161static const struct i2c_algorithm sgi_algo = {
162	.master_xfer	= sgi_xfer,
163	.functionality	= sgi_func,
164};
165
166/*
167 * registering functions to load algorithms at runtime
168 */
169int i2c_sgi_add_bus(struct i2c_adapter *adap)
170{
171	adap->algo = &sgi_algo;
172
173	return i2c_add_adapter(adap);
174}
175EXPORT_SYMBOL(i2c_sgi_add_bus);
176
177MODULE_AUTHOR("Ladislav Michl <ladis@linux-mips.org>");
178MODULE_DESCRIPTION("I2C-Bus SGI algorithm");
179MODULE_LICENSE("GPL");
180