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 busions 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 "bus.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 nvkm_i2c_drive_scl(struct nvkm_i2c_bus *bus, int state)
33 {
34 	bus->func->drive_scl(bus, state);
35 }
36 
37 static inline void
38 nvkm_i2c_drive_sda(struct nvkm_i2c_bus *bus, int state)
39 {
40 	bus->func->drive_sda(bus, state);
41 }
42 
43 static inline int
44 nvkm_i2c_sense_scl(struct nvkm_i2c_bus *bus)
45 {
46 	return bus->func->sense_scl(bus);
47 }
48 
49 static inline int
50 nvkm_i2c_sense_sda(struct nvkm_i2c_bus *bus)
51 {
52 	return bus->func->sense_sda(bus);
53 }
54 
55 static void
56 nvkm_i2c_delay(struct nvkm_i2c_bus *bus, u32 nsec)
57 {
58 	udelay((nsec + 500) / 1000);
59 }
60 
61 static bool
62 nvkm_i2c_raise_scl(struct nvkm_i2c_bus *bus)
63 {
64 	u32 timeout = T_TIMEOUT / T_RISEFALL;
65 
66 	nvkm_i2c_drive_scl(bus, 1);
67 	do {
68 		nvkm_i2c_delay(bus, T_RISEFALL);
69 	} while (!nvkm_i2c_sense_scl(bus) && --timeout);
70 
71 	return timeout != 0;
72 }
73 
74 static int
75 i2c_start(struct nvkm_i2c_bus *bus)
76 {
77 	int ret = 0;
78 
79 	if (!nvkm_i2c_sense_scl(bus) ||
80 	    !nvkm_i2c_sense_sda(bus)) {
81 		nvkm_i2c_drive_scl(bus, 0);
82 		nvkm_i2c_drive_sda(bus, 1);
83 		if (!nvkm_i2c_raise_scl(bus))
84 			ret = -EBUSY;
85 	}
86 
87 	nvkm_i2c_drive_sda(bus, 0);
88 	nvkm_i2c_delay(bus, T_HOLD);
89 	nvkm_i2c_drive_scl(bus, 0);
90 	nvkm_i2c_delay(bus, T_HOLD);
91 	return ret;
92 }
93 
94 static void
95 i2c_stop(struct nvkm_i2c_bus *bus)
96 {
97 	nvkm_i2c_drive_scl(bus, 0);
98 	nvkm_i2c_drive_sda(bus, 0);
99 	nvkm_i2c_delay(bus, T_RISEFALL);
100 
101 	nvkm_i2c_drive_scl(bus, 1);
102 	nvkm_i2c_delay(bus, T_HOLD);
103 	nvkm_i2c_drive_sda(bus, 1);
104 	nvkm_i2c_delay(bus, T_HOLD);
105 }
106 
107 static int
108 i2c_bitw(struct nvkm_i2c_bus *bus, int sda)
109 {
110 	nvkm_i2c_drive_sda(bus, sda);
111 	nvkm_i2c_delay(bus, T_RISEFALL);
112 
113 	if (!nvkm_i2c_raise_scl(bus))
114 		return -ETIMEDOUT;
115 	nvkm_i2c_delay(bus, T_HOLD);
116 
117 	nvkm_i2c_drive_scl(bus, 0);
118 	nvkm_i2c_delay(bus, T_HOLD);
119 	return 0;
120 }
121 
122 static int
123 i2c_bitr(struct nvkm_i2c_bus *bus)
124 {
125 	int sda;
126 
127 	nvkm_i2c_drive_sda(bus, 1);
128 	nvkm_i2c_delay(bus, T_RISEFALL);
129 
130 	if (!nvkm_i2c_raise_scl(bus))
131 		return -ETIMEDOUT;
132 	nvkm_i2c_delay(bus, T_HOLD);
133 
134 	sda = nvkm_i2c_sense_sda(bus);
135 
136 	nvkm_i2c_drive_scl(bus, 0);
137 	nvkm_i2c_delay(bus, T_HOLD);
138 	return sda;
139 }
140 
141 static int
142 nvkm_i2c_get_byte(struct nvkm_i2c_bus *bus, u8 *byte, bool last)
143 {
144 	int i, bit;
145 
146 	*byte = 0;
147 	for (i = 7; i >= 0; i--) {
148 		bit = i2c_bitr(bus);
149 		if (bit < 0)
150 			return bit;
151 		*byte |= bit << i;
152 	}
153 
154 	return i2c_bitw(bus, last ? 1 : 0);
155 }
156 
157 static int
158 nvkm_i2c_put_byte(struct nvkm_i2c_bus *bus, u8 byte)
159 {
160 	int i, ret;
161 	for (i = 7; i >= 0; i--) {
162 		ret = i2c_bitw(bus, !!(byte & (1 << i)));
163 		if (ret < 0)
164 			return ret;
165 	}
166 
167 	ret = i2c_bitr(bus);
168 	if (ret == 1) /* nack */
169 		ret = -EIO;
170 	return ret;
171 }
172 
173 static int
174 i2c_addr(struct nvkm_i2c_bus *bus, struct i2c_msg *msg)
175 {
176 	u32 addr = msg->addr << 1;
177 	if (msg->flags & I2C_M_RD)
178 		addr |= 1;
179 	return nvkm_i2c_put_byte(bus, addr);
180 }
181 
182 int
183 nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
184 {
185 	struct i2c_msg *msg = msgs;
186 	int ret = 0, mcnt = num;
187 
188 	while (!ret && mcnt--) {
189 		u8 remaining = msg->len;
190 		u8 *ptr = msg->buf;
191 
192 		ret = i2c_start(bus);
193 		if (ret == 0)
194 			ret = i2c_addr(bus, msg);
195 
196 		if (msg->flags & I2C_M_RD) {
197 			while (!ret && remaining--)
198 				ret = nvkm_i2c_get_byte(bus, ptr++, !remaining);
199 		} else {
200 			while (!ret && remaining--)
201 				ret = nvkm_i2c_put_byte(bus, *ptr++);
202 		}
203 
204 		msg++;
205 	}
206 
207 	i2c_stop(bus);
208 	return (ret < 0) ? ret : num;
209 }
210 #else
211 int
212 nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
213 {
214 	return -ENODEV;
215 }
216 #endif
217