1 /*
2  * Copyright 2012 Red Hat Inc.
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
17  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20  * OTHER DEALINGS IN THE SOFTWARE.
21  *
22  * Authors: Ben Skeggs
23  */
24 #include "priv.h"
25 
26 #ifdef CONFIG_NOUVEAU_I2C_INTERNAL
27 #define T_TIMEOUT  2200000
28 #define T_RISEFALL 1000
29 #define T_HOLD     5000
30 
31 static inline void
32 i2c_drive_scl(struct nvkm_i2c_port *port, int state)
33 {
34 	port->func->drive_scl(port, state);
35 }
36 
37 static inline void
38 i2c_drive_sda(struct nvkm_i2c_port *port, int state)
39 {
40 	port->func->drive_sda(port, state);
41 }
42 
43 static inline int
44 i2c_sense_scl(struct nvkm_i2c_port *port)
45 {
46 	return port->func->sense_scl(port);
47 }
48 
49 static inline int
50 i2c_sense_sda(struct nvkm_i2c_port *port)
51 {
52 	return port->func->sense_sda(port);
53 }
54 
55 static void
56 i2c_delay(struct nvkm_i2c_port *port, u32 nsec)
57 {
58 	udelay((nsec + 500) / 1000);
59 }
60 
61 static bool
62 i2c_raise_scl(struct nvkm_i2c_port *port)
63 {
64 	u32 timeout = T_TIMEOUT / T_RISEFALL;
65 
66 	i2c_drive_scl(port, 1);
67 	do {
68 		i2c_delay(port, T_RISEFALL);
69 	} while (!i2c_sense_scl(port) && --timeout);
70 
71 	return timeout != 0;
72 }
73 
74 static int
75 i2c_start(struct nvkm_i2c_port *port)
76 {
77 	int ret = 0;
78 
79 	if (!i2c_sense_scl(port) ||
80 	    !i2c_sense_sda(port)) {
81 		i2c_drive_scl(port, 0);
82 		i2c_drive_sda(port, 1);
83 		if (!i2c_raise_scl(port))
84 			ret = -EBUSY;
85 	}
86 
87 	i2c_drive_sda(port, 0);
88 	i2c_delay(port, T_HOLD);
89 	i2c_drive_scl(port, 0);
90 	i2c_delay(port, T_HOLD);
91 	return ret;
92 }
93 
94 static void
95 i2c_stop(struct nvkm_i2c_port *port)
96 {
97 	i2c_drive_scl(port, 0);
98 	i2c_drive_sda(port, 0);
99 	i2c_delay(port, T_RISEFALL);
100 
101 	i2c_drive_scl(port, 1);
102 	i2c_delay(port, T_HOLD);
103 	i2c_drive_sda(port, 1);
104 	i2c_delay(port, T_HOLD);
105 }
106 
107 static int
108 i2c_bitw(struct nvkm_i2c_port *port, int sda)
109 {
110 	i2c_drive_sda(port, sda);
111 	i2c_delay(port, T_RISEFALL);
112 
113 	if (!i2c_raise_scl(port))
114 		return -ETIMEDOUT;
115 	i2c_delay(port, T_HOLD);
116 
117 	i2c_drive_scl(port, 0);
118 	i2c_delay(port, T_HOLD);
119 	return 0;
120 }
121 
122 static int
123 i2c_bitr(struct nvkm_i2c_port *port)
124 {
125 	int sda;
126 
127 	i2c_drive_sda(port, 1);
128 	i2c_delay(port, T_RISEFALL);
129 
130 	if (!i2c_raise_scl(port))
131 		return -ETIMEDOUT;
132 	i2c_delay(port, T_HOLD);
133 
134 	sda = i2c_sense_sda(port);
135 
136 	i2c_drive_scl(port, 0);
137 	i2c_delay(port, T_HOLD);
138 	return sda;
139 }
140 
141 static int
142 i2c_get_byte(struct nvkm_i2c_port *port, u8 *byte, bool last)
143 {
144 	int i, bit;
145 
146 	*byte = 0;
147 	for (i = 7; i >= 0; i--) {
148 		bit = i2c_bitr(port);
149 		if (bit < 0)
150 			return bit;
151 		*byte |= bit << i;
152 	}
153 
154 	return i2c_bitw(port, last ? 1 : 0);
155 }
156 
157 static int
158 i2c_put_byte(struct nvkm_i2c_port *port, u8 byte)
159 {
160 	int i, ret;
161 	for (i = 7; i >= 0; i--) {
162 		ret = i2c_bitw(port, !!(byte & (1 << i)));
163 		if (ret < 0)
164 			return ret;
165 	}
166 
167 	ret = i2c_bitr(port);
168 	if (ret == 1) /* nack */
169 		ret = -EIO;
170 	return ret;
171 }
172 
173 static int
174 i2c_addr(struct nvkm_i2c_port *port, struct i2c_msg *msg)
175 {
176 	u32 addr = msg->addr << 1;
177 	if (msg->flags & I2C_M_RD)
178 		addr |= 1;
179 	return i2c_put_byte(port, addr);
180 }
181 
182 static int
183 i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
184 {
185 	struct nvkm_i2c_port *port = adap->algo_data;
186 	struct i2c_msg *msg = msgs;
187 	int ret = 0, mcnt = num;
188 
189 	ret = nvkm_i2c(port)->acquire(port, nsecs_to_jiffies(T_TIMEOUT));
190 	if (ret)
191 		return ret;
192 
193 	while (!ret && mcnt--) {
194 		u8 remaining = msg->len;
195 		u8 *ptr = msg->buf;
196 
197 		ret = i2c_start(port);
198 		if (ret == 0)
199 			ret = i2c_addr(port, msg);
200 
201 		if (msg->flags & I2C_M_RD) {
202 			while (!ret && remaining--)
203 				ret = i2c_get_byte(port, ptr++, !remaining);
204 		} else {
205 			while (!ret && remaining--)
206 				ret = i2c_put_byte(port, *ptr++);
207 		}
208 
209 		msg++;
210 	}
211 
212 	i2c_stop(port);
213 	nvkm_i2c(port)->release(port);
214 	return (ret < 0) ? ret : num;
215 }
216 #else
217 static int
218 i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
219 {
220 	return -ENODEV;
221 }
222 #endif
223 
224 static u32
225 i2c_bit_func(struct i2c_adapter *adap)
226 {
227 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
228 }
229 
230 const struct i2c_algorithm nvkm_i2c_bit_algo = {
231 	.master_xfer = i2c_bit_xfer,
232 	.functionality = i2c_bit_func
233 };
234