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