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
40 static 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
53 static 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
68 static 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;
79 out:
80 if (get_control() & SGI_I2C_BUS_ERR)
81 return -EIO;
82 return 0;
83 }
84
85 static 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
104 static 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
121 static 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
135 static 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
156 static u32 sgi_func(struct i2c_adapter *adap)
157 {
158 return I2C_FUNC_SMBUS_EMUL;
159 }
160
161 static 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 */
169 int i2c_sgi_add_bus(struct i2c_adapter *adap)
170 {
171 adap->algo = &sgi_algo;
172
173 return i2c_add_adapter(adap);
174 }
175 EXPORT_SYMBOL(i2c_sgi_add_bus);
176
177 MODULE_AUTHOR("Ladislav Michl <ladis@linux-mips.org>");
178 MODULE_DESCRIPTION("I2C-Bus SGI algorithm");
179 MODULE_LICENSE("GPL");
180
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