Angel Pons | c74dae9 | 2020-04-02 23:48:16 +0200 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 2 | |
| 3 | #include <assert.h> |
| 4 | #include <timer.h> |
| 5 | #include <console/console.h> |
Nico Huber | 0f2dd1e | 2017-08-01 14:02:40 +0200 | [diff] [blame] | 6 | #include <device/i2c_simple.h> |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 7 | |
| 8 | /* |
| 9 | * The implementation is based on Wikipedia. |
| 10 | */ |
| 11 | |
| 12 | #define DEBUG 0 /* Set to 1 for per-byte output */ |
| 13 | #define SPEW 0 /* Set to 1 for verbose bitwise/line-state output */ |
| 14 | #define DELAY_US 5 /* Default setup delay: 4us (+1 for timer inaccuracy) */ |
| 15 | #define TIMEOUT_US 50000 /* Maximum clock stretching time we want to allow */ |
| 16 | |
| 17 | #define spew(...) do { if (SPEW) printk(BIOS_SPEW, ##__VA_ARGS__); } while (0) |
| 18 | |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 19 | #define ERR_NACK -2 |
| 20 | #define ERR_TIMEOUT -3 |
| 21 | #define ERR_ARB -4 |
| 22 | #define ERR_WEDGE -5 |
| 23 | |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 24 | struct software_i2c_ops *software_i2c[SOFTWARE_I2C_MAX_BUS]; |
| 25 | |
| 26 | /* |
| 27 | * Waits until either timeout_us have passed or (iff for_scl is set) until SCL |
| 28 | * goes high. Will report random line changes during the wait and return SCL. |
| 29 | */ |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 30 | static int __wait(unsigned int bus, int timeout_us, int for_scl) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 31 | { |
| 32 | int us; |
| 33 | int sda = software_i2c[bus]->get_sda(bus); |
| 34 | int scl = software_i2c[bus]->get_scl(bus); |
Aaron Durbin | 46ba480 | 2014-09-23 16:34:40 -0500 | [diff] [blame] | 35 | struct stopwatch sw; |
| 36 | |
| 37 | stopwatch_init_usecs_expire(&sw, timeout_us); |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 38 | |
| 39 | do { |
| 40 | int old_sda = sda; |
| 41 | int old_scl = scl; |
Aaron Durbin | 46ba480 | 2014-09-23 16:34:40 -0500 | [diff] [blame] | 42 | |
| 43 | us = stopwatch_duration_usecs(&sw); |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 44 | |
| 45 | if (old_sda != (sda = software_i2c[bus]->get_sda(bus))) |
| 46 | spew("[SDA transitioned to %d after %dus] ", sda, us); |
| 47 | if (old_scl != (scl = software_i2c[bus]->get_scl(bus))) |
| 48 | spew("[SCL transitioned to %d after %dus] ", scl, us); |
Aaron Durbin | 46ba480 | 2014-09-23 16:34:40 -0500 | [diff] [blame] | 49 | } while (!stopwatch_expired(&sw) && (!for_scl || !scl)); |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 50 | |
| 51 | return scl; |
| 52 | } |
| 53 | |
| 54 | /* Waits the default DELAY_US to allow line state to stabilize. */ |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 55 | static void wait(unsigned int bus) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 56 | { |
| 57 | __wait(bus, DELAY_US, 0); |
| 58 | } |
| 59 | |
| 60 | /* Waits until SCL goes high. Prints a contextual error message on timeout. */ |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 61 | static int wait_for_scl(unsigned int bus, const char *error_context) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 62 | { |
| 63 | if (!__wait(bus, TIMEOUT_US, 1)) { |
| 64 | printk(BIOS_ERR, "software_i2c(%d): ERROR: Clock stretching " |
| 65 | "timeout %s!\n", bus, error_context); |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 66 | return ERR_TIMEOUT; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 67 | } |
| 68 | |
| 69 | return 0; |
| 70 | } |
| 71 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 72 | static int start_cond(unsigned int bus) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 73 | { |
| 74 | spew("software_i2c(%d): Sending start condition... ", bus); |
| 75 | |
| 76 | /* SDA might not yet be high if repeated start. */ |
| 77 | software_i2c[bus]->set_sda(bus, 1); |
| 78 | wait(bus); |
| 79 | |
| 80 | /* Might need to wait for clock stretching if repeated start. */ |
| 81 | software_i2c[bus]->set_scl(bus, 1); |
| 82 | if (wait_for_scl(bus, "before start condition")) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 83 | return ERR_TIMEOUT; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 84 | wait(bus); /* Repeated start setup time, minimum 4.7us */ |
| 85 | |
| 86 | if (!software_i2c[bus]->get_sda(bus)) { |
| 87 | printk(BIOS_ERR, "software_i2c(%d): Arbitration lost trying " |
| 88 | "to send start condition!\n", bus); |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 89 | return ERR_ARB; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 90 | } |
| 91 | |
| 92 | /* SCL is high, transition SDA low as first part of start condition. */ |
| 93 | software_i2c[bus]->set_sda(bus, 0); |
| 94 | wait(bus); |
| 95 | assert(software_i2c[bus]->get_scl(bus)); |
| 96 | |
| 97 | /* Pull SCL low to finish start condition (next pulse will be data). */ |
| 98 | software_i2c[bus]->set_scl(bus, 0); |
| 99 | |
| 100 | spew("Start condition transmitted!\n"); |
| 101 | return 0; |
| 102 | } |
| 103 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 104 | static int stop_cond(unsigned int bus) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 105 | { |
| 106 | spew("software_i2c(%d): Sending stop condition... ", bus); |
| 107 | |
| 108 | /* SDA is unknown, set it to low. SCL must be low. */ |
| 109 | software_i2c[bus]->set_sda(bus, 0); |
| 110 | wait(bus); |
| 111 | |
| 112 | /* Clock stretching */ |
| 113 | assert(!software_i2c[bus]->get_scl(bus)); |
| 114 | software_i2c[bus]->set_scl(bus, 1); |
| 115 | if (wait_for_scl(bus, "before stop condition")) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 116 | return ERR_TIMEOUT; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 117 | wait(bus); /* Stop bit setup time, minimum 4us */ |
| 118 | |
| 119 | /* SCL is high, transition SDA high to signal stop condition. */ |
| 120 | software_i2c[bus]->set_sda(bus, 1); |
| 121 | wait(bus); |
| 122 | if (!software_i2c[bus]->get_sda(bus)) { |
| 123 | printk(BIOS_WARNING, "software_i2c(%d): WARNING: SDA low after " |
| 124 | "stop condition... access by another master or line " |
| 125 | "stuck from faulty slave?\n", bus); |
| 126 | /* Could theoretically happen with multi-master, so no -1. */ |
| 127 | } |
| 128 | |
| 129 | spew("Stop condition transmitted\n"); |
| 130 | return 0; |
| 131 | } |
| 132 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 133 | static int out_bit(unsigned int bus, int bit) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 134 | { |
| 135 | spew("software_i2c(%d): Sending a %d bit... ", bus, bit); |
| 136 | |
| 137 | software_i2c[bus]->set_sda(bus, bit); |
| 138 | wait(bus); |
| 139 | |
| 140 | if (bit && !software_i2c[bus]->get_sda(bus)) { |
| 141 | printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low " |
| 142 | "by slave before clock pulse on transmit!\n", bus); |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 143 | return ERR_WEDGE; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 144 | } |
| 145 | |
| 146 | /* Clock stretching */ |
| 147 | assert(!software_i2c[bus]->get_scl(bus)); |
| 148 | software_i2c[bus]->set_scl(bus, 1); |
| 149 | if (wait_for_scl(bus, "on transmit")) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 150 | return ERR_TIMEOUT; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 151 | wait(bus); |
| 152 | |
| 153 | if (bit && !software_i2c[bus]->get_sda(bus)) { |
| 154 | printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low " |
| 155 | "by slave after clock pulse on transmit!\n", bus); |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 156 | return ERR_WEDGE; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 157 | } |
| 158 | |
| 159 | assert(software_i2c[bus]->get_scl(bus)); |
| 160 | software_i2c[bus]->set_scl(bus, 0); |
| 161 | |
| 162 | spew("%d bit sent!\n", bit); |
| 163 | return 0; |
| 164 | } |
| 165 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 166 | static int in_bit(unsigned int bus) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 167 | { |
| 168 | int bit; |
| 169 | |
| 170 | spew("software_i2c(%d): Receiving a bit... ", bus); |
| 171 | |
| 172 | /* Let the slave drive data */ |
| 173 | software_i2c[bus]->set_sda(bus, 1); |
| 174 | wait(bus); |
| 175 | |
| 176 | /* Clock stretching */ |
| 177 | assert(!software_i2c[bus]->get_scl(bus)); |
| 178 | software_i2c[bus]->set_scl(bus, 1); |
| 179 | if (wait_for_scl(bus, "on receive")) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 180 | return ERR_TIMEOUT; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 181 | |
| 182 | /* SCL is high, now data is valid */ |
| 183 | bit = software_i2c[bus]->get_sda(bus); |
| 184 | wait(bus); |
| 185 | assert(software_i2c[bus]->get_scl(bus)); |
| 186 | software_i2c[bus]->set_scl(bus, 0); |
| 187 | |
| 188 | spew("Received a %d!\n", bit); |
| 189 | |
| 190 | return bit; |
| 191 | } |
| 192 | |
| 193 | /* Write a byte to I2C bus. Return 0 if ack by the slave. */ |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 194 | static int out_byte(unsigned int bus, u8 byte) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 195 | { |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 196 | unsigned int bit; |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 197 | int nack, ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 198 | |
| 199 | for (bit = 0; bit < 8; bit++) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 200 | if ((ret = out_bit(bus, (byte >> (7 - bit)) & 0x1)) < 0) |
| 201 | return ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 202 | |
| 203 | nack = in_bit(bus); |
| 204 | |
| 205 | if (DEBUG && nack >= 0) |
| 206 | printk(BIOS_DEBUG, "software_i2c(%d): wrote byte 0x%02x, " |
| 207 | "received %s\n", bus, byte, nack ? "NAK" : "ACK"); |
| 208 | |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 209 | return nack > 0 ? ERR_NACK : nack; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 210 | } |
| 211 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 212 | static int in_byte(unsigned int bus, int ack) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 213 | { |
| 214 | u8 byte = 0; |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 215 | int i, ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 216 | for (i = 0; i < 8; ++i) { |
| 217 | int bit = in_bit(bus); |
| 218 | if (bit < 0) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 219 | return bit; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 220 | byte = (byte << 1) | bit; |
| 221 | } |
| 222 | |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 223 | if ((ret = out_bit(bus, !ack)) < 0) |
| 224 | return ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 225 | |
| 226 | if (DEBUG) |
| 227 | printk(BIOS_DEBUG, "software_i2c(%d): read byte 0x%02x, " |
| 228 | "sent %s\n", bus, byte, ack ? "ACK" : "NAK"); |
| 229 | |
| 230 | return byte; |
| 231 | } |
| 232 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 233 | int software_i2c_transfer(unsigned int bus, struct i2c_msg *segments, int count) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 234 | { |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 235 | int i, ret; |
Nico Huber | 029dfff | 2017-07-12 17:59:16 +0200 | [diff] [blame] | 236 | struct i2c_msg *seg; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 237 | |
| 238 | for (seg = segments; seg - segments < count; seg++) { |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 239 | if ((ret = start_cond(bus)) < 0) |
| 240 | return ret; |
Nico Huber | 029dfff | 2017-07-12 17:59:16 +0200 | [diff] [blame] | 241 | const u8 addr_dir = seg->slave << 1 | !!(seg->flags & I2C_M_RD); |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 242 | if ((ret = out_byte(bus, addr_dir)) < 0) |
| 243 | return ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 244 | for (i = 0; i < seg->len; i++) { |
Nico Huber | 029dfff | 2017-07-12 17:59:16 +0200 | [diff] [blame] | 245 | if (seg->flags & I2C_M_RD) { |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 246 | ret = in_byte(bus, i < seg->len - 1); |
| 247 | seg->buf[i] = (u8)ret; |
| 248 | } else { |
| 249 | ret = out_byte(bus, seg->buf[i]); |
| 250 | } |
| 251 | if (ret < 0) |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 252 | return ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 253 | } |
| 254 | } |
Julius Werner | 6dc7b22 | 2018-04-30 17:57:08 -0700 | [diff] [blame] | 255 | if ((ret = stop_cond(bus)) < 0) |
| 256 | return ret; |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 257 | |
| 258 | return 0; |
| 259 | } |
| 260 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 261 | void software_i2c_wedge_ack(unsigned int bus, u8 chip) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 262 | { |
| 263 | int i; |
| 264 | |
| 265 | /* Start a command to 'chip'... */ |
| 266 | start_cond(bus); |
| 267 | |
| 268 | /* Send the address bits but don't yet read the ACK. */ |
| 269 | chip <<= 1; |
| 270 | for (i = 0; i < 8; ++i) |
| 271 | out_bit(bus, (chip >> (7 - i)) & 0x1); |
| 272 | |
| 273 | /* Let the slave drive it's ACK but keep the clock high forever. */ |
| 274 | software_i2c[bus]->set_sda(bus, 1); |
| 275 | wait(bus); |
| 276 | software_i2c[bus]->set_scl(bus, 1); |
| 277 | wait_for_scl(bus, "on wedge_ack()"); |
| 278 | |
| 279 | printk(BIOS_INFO, "software_i2c(%d): wedged address write on slave " |
| 280 | "ACK. SDA %d, SCL %d\n", bus, software_i2c[bus]->get_sda(bus), |
| 281 | software_i2c[bus]->get_scl(bus)); |
| 282 | } |
| 283 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 284 | void software_i2c_wedge_read(unsigned int bus, u8 chip, u8 reg, int bits) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 285 | { |
| 286 | int i; |
| 287 | |
| 288 | /* Start a command to 'chip'... */ |
| 289 | start_cond(bus); |
| 290 | out_byte(bus, chip << 1); |
| 291 | /* ...for register 'reg'. */ |
| 292 | out_byte(bus, reg); |
| 293 | |
| 294 | /* Start a read command... */ |
| 295 | start_cond(bus); |
| 296 | out_byte(bus, chip << 1 | 1); |
| 297 | |
| 298 | /* Read bit_count bits and stop */ |
| 299 | for (i = 0; i < bits; ++i) |
| 300 | in_bit(bus); |
| 301 | |
| 302 | /* Let the slave drive SDA but keep the clock high forever. */ |
| 303 | software_i2c[bus]->set_sda(bus, 1); |
| 304 | wait(bus); |
| 305 | software_i2c[bus]->set_scl(bus, 1); |
| 306 | wait_for_scl(bus, "on wedge_read()"); |
| 307 | |
| 308 | printk(BIOS_INFO, "software_i2c(%d): wedged data read after %d bits. " |
| 309 | "SDA %d, SCL %d\n", bus, bits, software_i2c[bus]->get_sda(bus), |
| 310 | software_i2c[bus]->get_scl(bus)); |
| 311 | } |
| 312 | |
Martin Roth | 38ddbfb | 2019-10-23 21:41:00 -0600 | [diff] [blame] | 313 | void software_i2c_wedge_write(unsigned int bus, u8 chip, u8 reg, int bits) |
Julius Werner | 37d7ac8 | 2014-05-05 18:03:46 -0700 | [diff] [blame] | 314 | { |
| 315 | int i; |
| 316 | |
| 317 | /* Start a command to 'chip'... */ |
| 318 | start_cond(bus); |
| 319 | out_byte(bus, chip << 1); |
| 320 | |
| 321 | /* Write bit_count register bits and stop */ |
| 322 | for (i = 0; i < bits; ++i) |
| 323 | out_bit(bus, (reg >> (7 - i)) & 0x1); |
| 324 | |
| 325 | /* Pretend to write another 1 bit but keep the clock high forever. */ |
| 326 | software_i2c[bus]->set_sda(bus, 1); |
| 327 | wait(bus); |
| 328 | software_i2c[bus]->set_scl(bus, 1); |
| 329 | wait_for_scl(bus, "on wedge_write()"); |
| 330 | |
| 331 | printk(BIOS_INFO, "software_i2c(%d): wedged data write after %d bits. " |
| 332 | "SDA %d, SCL %d\n", bus, bits, software_i2c[bus]->get_sda(bus), |
| 333 | software_i2c[bus]->get_scl(bus)); |
| 334 | } |