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