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
nvkm_i2c_drive_scl(struct nvkm_i2c_bus * bus,int state)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
nvkm_i2c_drive_sda(struct nvkm_i2c_bus * bus,int state)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
nvkm_i2c_sense_scl(struct nvkm_i2c_bus * bus)44 nvkm_i2c_sense_scl(struct nvkm_i2c_bus *bus)
45 {
46 return bus->func->sense_scl(bus);
47 }
48
49 static inline int
nvkm_i2c_sense_sda(struct nvkm_i2c_bus * bus)50 nvkm_i2c_sense_sda(struct nvkm_i2c_bus *bus)
51 {
52 return bus->func->sense_sda(bus);
53 }
54
55 static void
nvkm_i2c_delay(struct nvkm_i2c_bus * bus,u32 nsec)56 nvkm_i2c_delay(struct nvkm_i2c_bus *bus, u32 nsec)
57 {
58 udelay((nsec + 500) / 1000);
59 }
60
61 static bool
nvkm_i2c_raise_scl(struct nvkm_i2c_bus * bus)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
i2c_start(struct nvkm_i2c_bus * bus)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
i2c_stop(struct nvkm_i2c_bus * bus)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
i2c_bitw(struct nvkm_i2c_bus * bus,int sda)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
i2c_bitr(struct nvkm_i2c_bus * bus)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
nvkm_i2c_get_byte(struct nvkm_i2c_bus * bus,u8 * byte,bool last)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
nvkm_i2c_put_byte(struct nvkm_i2c_bus * bus,u8 byte)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
i2c_addr(struct nvkm_i2c_bus * bus,struct i2c_msg * msg)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
nvkm_i2c_bit_xfer(struct nvkm_i2c_bus * bus,struct i2c_msg * msgs,int num)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
nvkm_i2c_bit_xfer(struct nvkm_i2c_bus * bus,struct i2c_msg * msgs,int num)212 nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
213 {
214 return -ENODEV;
215 }
216 #endif
217