Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 1 | /* |
| 2 | * I2C multiplexer driver for PCA9541 bus master selector |
| 3 | * |
| 4 | * Copyright (c) 2010 Ericsson AB. |
| 5 | * |
Guenter Roeck | b104153 | 2013-02-26 06:03:52 +0000 | [diff] [blame] | 6 | * Author: Guenter Roeck <linux@roeck-us.net> |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 7 | * |
| 8 | * Derived from: |
| 9 | * pca954x.c |
| 10 | * |
| 11 | * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it> |
| 12 | * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it> |
| 13 | * |
| 14 | * This file is licensed under the terms of the GNU General Public |
| 15 | * License version 2. This program is licensed "as is" without any |
| 16 | * warranty of any kind, whether express or implied. |
| 17 | */ |
| 18 | |
| 19 | #include <linux/module.h> |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 20 | #include <linux/jiffies.h> |
| 21 | #include <linux/delay.h> |
| 22 | #include <linux/slab.h> |
| 23 | #include <linux/device.h> |
| 24 | #include <linux/i2c.h> |
| 25 | #include <linux/i2c-mux.h> |
| 26 | |
| 27 | #include <linux/i2c/pca954x.h> |
| 28 | |
| 29 | /* |
| 30 | * The PCA9541 is a bus master selector. It supports two I2C masters connected |
| 31 | * to a single slave bus. |
| 32 | * |
| 33 | * Before each bus transaction, a master has to acquire bus ownership. After the |
| 34 | * transaction is complete, bus ownership has to be released. This fits well |
| 35 | * into the I2C multiplexer framework, which provides select and release |
| 36 | * functions for this purpose. For this reason, this driver is modeled as |
| 37 | * single-channel I2C bus multiplexer. |
| 38 | * |
| 39 | * This driver assumes that the two bus masters are controlled by two different |
| 40 | * hosts. If a single host controls both masters, platform code has to ensure |
| 41 | * that only one of the masters is instantiated at any given time. |
| 42 | */ |
| 43 | |
| 44 | #define PCA9541_CONTROL 0x01 |
| 45 | #define PCA9541_ISTAT 0x02 |
| 46 | |
| 47 | #define PCA9541_CTL_MYBUS (1 << 0) |
| 48 | #define PCA9541_CTL_NMYBUS (1 << 1) |
| 49 | #define PCA9541_CTL_BUSON (1 << 2) |
| 50 | #define PCA9541_CTL_NBUSON (1 << 3) |
| 51 | #define PCA9541_CTL_BUSINIT (1 << 4) |
| 52 | #define PCA9541_CTL_TESTON (1 << 6) |
| 53 | #define PCA9541_CTL_NTESTON (1 << 7) |
| 54 | |
| 55 | #define PCA9541_ISTAT_INTIN (1 << 0) |
| 56 | #define PCA9541_ISTAT_BUSINIT (1 << 1) |
| 57 | #define PCA9541_ISTAT_BUSOK (1 << 2) |
| 58 | #define PCA9541_ISTAT_BUSLOST (1 << 3) |
| 59 | #define PCA9541_ISTAT_MYTEST (1 << 6) |
| 60 | #define PCA9541_ISTAT_NMYTEST (1 << 7) |
| 61 | |
| 62 | #define BUSON (PCA9541_CTL_BUSON | PCA9541_CTL_NBUSON) |
| 63 | #define MYBUS (PCA9541_CTL_MYBUS | PCA9541_CTL_NMYBUS) |
| 64 | #define mybus(x) (!((x) & MYBUS) || ((x) & MYBUS) == MYBUS) |
| 65 | #define busoff(x) (!((x) & BUSON) || ((x) & BUSON) == BUSON) |
| 66 | |
| 67 | /* arbitration timeouts, in jiffies */ |
| 68 | #define ARB_TIMEOUT (HZ / 8) /* 125 ms until forcing bus ownership */ |
| 69 | #define ARB2_TIMEOUT (HZ / 4) /* 250 ms until acquisition failure */ |
| 70 | |
| 71 | /* arbitration retry delays, in us */ |
| 72 | #define SELECT_DELAY_SHORT 50 |
| 73 | #define SELECT_DELAY_LONG 1000 |
| 74 | |
| 75 | struct pca9541 { |
| 76 | struct i2c_adapter *mux_adap; |
| 77 | unsigned long select_timeout; |
| 78 | unsigned long arb_timeout; |
| 79 | }; |
| 80 | |
| 81 | static const struct i2c_device_id pca9541_id[] = { |
| 82 | {"pca9541", 0}, |
| 83 | {} |
| 84 | }; |
| 85 | |
| 86 | MODULE_DEVICE_TABLE(i2c, pca9541_id); |
| 87 | |
| 88 | /* |
| 89 | * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer() |
| 90 | * as they will try to lock the adapter a second time. |
| 91 | */ |
| 92 | static int pca9541_reg_write(struct i2c_client *client, u8 command, u8 val) |
| 93 | { |
| 94 | struct i2c_adapter *adap = client->adapter; |
| 95 | int ret; |
| 96 | |
| 97 | if (adap->algo->master_xfer) { |
| 98 | struct i2c_msg msg; |
| 99 | char buf[2]; |
| 100 | |
| 101 | msg.addr = client->addr; |
| 102 | msg.flags = 0; |
| 103 | msg.len = 2; |
| 104 | buf[0] = command; |
| 105 | buf[1] = val; |
| 106 | msg.buf = buf; |
| 107 | ret = adap->algo->master_xfer(adap, &msg, 1); |
| 108 | } else { |
| 109 | union i2c_smbus_data data; |
| 110 | |
| 111 | data.byte = val; |
| 112 | ret = adap->algo->smbus_xfer(adap, client->addr, |
| 113 | client->flags, |
| 114 | I2C_SMBUS_WRITE, |
| 115 | command, |
| 116 | I2C_SMBUS_BYTE_DATA, &data); |
| 117 | } |
| 118 | |
| 119 | return ret; |
| 120 | } |
| 121 | |
| 122 | /* |
| 123 | * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer() |
| 124 | * as they will try to lock adapter a second time. |
| 125 | */ |
| 126 | static int pca9541_reg_read(struct i2c_client *client, u8 command) |
| 127 | { |
| 128 | struct i2c_adapter *adap = client->adapter; |
| 129 | int ret; |
| 130 | u8 val; |
| 131 | |
| 132 | if (adap->algo->master_xfer) { |
| 133 | struct i2c_msg msg[2] = { |
| 134 | { |
| 135 | .addr = client->addr, |
| 136 | .flags = 0, |
| 137 | .len = 1, |
| 138 | .buf = &command |
| 139 | }, |
| 140 | { |
| 141 | .addr = client->addr, |
| 142 | .flags = I2C_M_RD, |
| 143 | .len = 1, |
| 144 | .buf = &val |
| 145 | } |
| 146 | }; |
| 147 | ret = adap->algo->master_xfer(adap, msg, 2); |
| 148 | if (ret == 2) |
| 149 | ret = val; |
| 150 | else if (ret >= 0) |
| 151 | ret = -EIO; |
| 152 | } else { |
| 153 | union i2c_smbus_data data; |
| 154 | |
| 155 | ret = adap->algo->smbus_xfer(adap, client->addr, |
| 156 | client->flags, |
| 157 | I2C_SMBUS_READ, |
| 158 | command, |
| 159 | I2C_SMBUS_BYTE_DATA, &data); |
| 160 | if (!ret) |
| 161 | ret = data.byte; |
| 162 | } |
| 163 | return ret; |
| 164 | } |
| 165 | |
| 166 | /* |
| 167 | * Arbitration management functions |
| 168 | */ |
| 169 | |
| 170 | /* Release bus. Also reset NTESTON and BUSINIT if it was set. */ |
| 171 | static void pca9541_release_bus(struct i2c_client *client) |
| 172 | { |
| 173 | int reg; |
| 174 | |
| 175 | reg = pca9541_reg_read(client, PCA9541_CONTROL); |
| 176 | if (reg >= 0 && !busoff(reg) && mybus(reg)) |
| 177 | pca9541_reg_write(client, PCA9541_CONTROL, |
| 178 | (reg & PCA9541_CTL_NBUSON) >> 1); |
| 179 | } |
| 180 | |
| 181 | /* |
| 182 | * Arbitration is defined as a two-step process. A bus master can only activate |
| 183 | * the slave bus if it owns it; otherwise it has to request ownership first. |
| 184 | * This multi-step process ensures that access contention is resolved |
| 185 | * gracefully. |
| 186 | * |
| 187 | * Bus Ownership Other master Action |
| 188 | * state requested access |
| 189 | * ---------------------------------------------------- |
| 190 | * off - yes wait for arbitration timeout or |
| 191 | * for other master to drop request |
| 192 | * off no no take ownership |
| 193 | * off yes no turn on bus |
| 194 | * on yes - done |
| 195 | * on no - wait for arbitration timeout or |
| 196 | * for other master to release bus |
| 197 | * |
| 198 | * The main contention point occurs if the slave bus is off and both masters |
| 199 | * request ownership at the same time. In this case, one master will turn on |
| 200 | * the slave bus, believing that it owns it. The other master will request |
| 201 | * bus ownership. Result is that the bus is turned on, and master which did |
| 202 | * _not_ own the slave bus before ends up owning it. |
| 203 | */ |
| 204 | |
| 205 | /* Control commands per PCA9541 datasheet */ |
| 206 | static const u8 pca9541_control[16] = { |
| 207 | 4, 0, 1, 5, 4, 4, 5, 5, 0, 0, 1, 1, 0, 4, 5, 1 |
| 208 | }; |
| 209 | |
| 210 | /* |
| 211 | * Channel arbitration |
| 212 | * |
| 213 | * Return values: |
| 214 | * <0: error |
| 215 | * 0 : bus not acquired |
| 216 | * 1 : bus acquired |
| 217 | */ |
| 218 | static int pca9541_arbitrate(struct i2c_client *client) |
| 219 | { |
| 220 | struct pca9541 *data = i2c_get_clientdata(client); |
| 221 | int reg; |
| 222 | |
| 223 | reg = pca9541_reg_read(client, PCA9541_CONTROL); |
| 224 | if (reg < 0) |
| 225 | return reg; |
| 226 | |
| 227 | if (busoff(reg)) { |
| 228 | int istat; |
| 229 | /* |
| 230 | * Bus is off. Request ownership or turn it on unless |
| 231 | * other master requested ownership. |
| 232 | */ |
| 233 | istat = pca9541_reg_read(client, PCA9541_ISTAT); |
| 234 | if (!(istat & PCA9541_ISTAT_NMYTEST) |
| 235 | || time_is_before_eq_jiffies(data->arb_timeout)) { |
| 236 | /* |
| 237 | * Other master did not request ownership, |
| 238 | * or arbitration timeout expired. Take the bus. |
| 239 | */ |
| 240 | pca9541_reg_write(client, |
| 241 | PCA9541_CONTROL, |
| 242 | pca9541_control[reg & 0x0f] |
| 243 | | PCA9541_CTL_NTESTON); |
| 244 | data->select_timeout = SELECT_DELAY_SHORT; |
| 245 | } else { |
| 246 | /* |
| 247 | * Other master requested ownership. |
| 248 | * Set extra long timeout to give it time to acquire it. |
| 249 | */ |
| 250 | data->select_timeout = SELECT_DELAY_LONG * 2; |
| 251 | } |
| 252 | } else if (mybus(reg)) { |
| 253 | /* |
| 254 | * Bus is on, and we own it. We are done with acquisition. |
| 255 | * Reset NTESTON and BUSINIT, then return success. |
| 256 | */ |
| 257 | if (reg & (PCA9541_CTL_NTESTON | PCA9541_CTL_BUSINIT)) |
| 258 | pca9541_reg_write(client, |
| 259 | PCA9541_CONTROL, |
| 260 | reg & ~(PCA9541_CTL_NTESTON |
| 261 | | PCA9541_CTL_BUSINIT)); |
| 262 | return 1; |
| 263 | } else { |
| 264 | /* |
| 265 | * Other master owns the bus. |
| 266 | * If arbitration timeout has expired, force ownership. |
| 267 | * Otherwise request it. |
| 268 | */ |
| 269 | data->select_timeout = SELECT_DELAY_LONG; |
| 270 | if (time_is_before_eq_jiffies(data->arb_timeout)) { |
| 271 | /* Time is up, take the bus and reset it. */ |
| 272 | pca9541_reg_write(client, |
| 273 | PCA9541_CONTROL, |
| 274 | pca9541_control[reg & 0x0f] |
| 275 | | PCA9541_CTL_BUSINIT |
| 276 | | PCA9541_CTL_NTESTON); |
| 277 | } else { |
| 278 | /* Request bus ownership if needed */ |
| 279 | if (!(reg & PCA9541_CTL_NTESTON)) |
| 280 | pca9541_reg_write(client, |
| 281 | PCA9541_CONTROL, |
| 282 | reg | PCA9541_CTL_NTESTON); |
| 283 | } |
| 284 | } |
| 285 | return 0; |
| 286 | } |
| 287 | |
| 288 | static int pca9541_select_chan(struct i2c_adapter *adap, void *client, u32 chan) |
| 289 | { |
| 290 | struct pca9541 *data = i2c_get_clientdata(client); |
| 291 | int ret; |
| 292 | unsigned long timeout = jiffies + ARB2_TIMEOUT; |
| 293 | /* give up after this time */ |
| 294 | |
| 295 | data->arb_timeout = jiffies + ARB_TIMEOUT; |
| 296 | /* force bus ownership after this time */ |
| 297 | |
| 298 | do { |
| 299 | ret = pca9541_arbitrate(client); |
| 300 | if (ret) |
| 301 | return ret < 0 ? ret : 0; |
| 302 | |
| 303 | if (data->select_timeout == SELECT_DELAY_SHORT) |
| 304 | udelay(data->select_timeout); |
| 305 | else |
| 306 | msleep(data->select_timeout / 1000); |
| 307 | } while (time_is_after_eq_jiffies(timeout)); |
| 308 | |
| 309 | return -ETIMEDOUT; |
| 310 | } |
| 311 | |
| 312 | static int pca9541_release_chan(struct i2c_adapter *adap, |
| 313 | void *client, u32 chan) |
| 314 | { |
| 315 | pca9541_release_bus(client); |
| 316 | return 0; |
| 317 | } |
| 318 | |
| 319 | /* |
| 320 | * I2C init/probing/exit functions |
| 321 | */ |
| 322 | static int pca9541_probe(struct i2c_client *client, |
| 323 | const struct i2c_device_id *id) |
| 324 | { |
| 325 | struct i2c_adapter *adap = client->adapter; |
Jingoo Han | 6d4028c | 2013-07-30 16:59:33 +0900 | [diff] [blame] | 326 | struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev); |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 327 | struct pca9541 *data; |
| 328 | int force; |
| 329 | int ret = -ENODEV; |
| 330 | |
| 331 | if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA)) |
| 332 | goto err; |
| 333 | |
| 334 | data = kzalloc(sizeof(struct pca9541), GFP_KERNEL); |
| 335 | if (!data) { |
| 336 | ret = -ENOMEM; |
| 337 | goto err; |
| 338 | } |
| 339 | |
| 340 | i2c_set_clientdata(client, data); |
| 341 | |
| 342 | /* |
| 343 | * I2C accesses are unprotected here. |
| 344 | * We have to lock the adapter before releasing the bus. |
| 345 | */ |
| 346 | i2c_lock_adapter(adap); |
| 347 | pca9541_release_bus(client); |
| 348 | i2c_unlock_adapter(adap); |
| 349 | |
| 350 | /* Create mux adapter */ |
| 351 | |
| 352 | force = 0; |
| 353 | if (pdata) |
| 354 | force = pdata->modes[0].adap_id; |
David Daney | 5a3ecd5 | 2012-04-12 14:14:22 -0700 | [diff] [blame] | 355 | data->mux_adap = i2c_add_mux_adapter(adap, &client->dev, client, |
Jean Delvare | eee543e | 2012-10-05 22:23:51 +0200 | [diff] [blame] | 356 | force, 0, 0, |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 357 | pca9541_select_chan, |
| 358 | pca9541_release_chan); |
| 359 | |
| 360 | if (data->mux_adap == NULL) { |
| 361 | dev_err(&client->dev, "failed to register master selector\n"); |
| 362 | goto exit_free; |
| 363 | } |
| 364 | |
| 365 | dev_info(&client->dev, "registered master selector for I2C %s\n", |
| 366 | client->name); |
| 367 | |
| 368 | return 0; |
| 369 | |
| 370 | exit_free: |
| 371 | kfree(data); |
| 372 | err: |
| 373 | return ret; |
| 374 | } |
| 375 | |
| 376 | static int pca9541_remove(struct i2c_client *client) |
| 377 | { |
| 378 | struct pca9541 *data = i2c_get_clientdata(client); |
| 379 | |
| 380 | i2c_del_mux_adapter(data->mux_adap); |
| 381 | |
| 382 | kfree(data); |
| 383 | return 0; |
| 384 | } |
| 385 | |
| 386 | static struct i2c_driver pca9541_driver = { |
| 387 | .driver = { |
| 388 | .name = "pca9541", |
| 389 | .owner = THIS_MODULE, |
| 390 | }, |
| 391 | .probe = pca9541_probe, |
| 392 | .remove = pca9541_remove, |
| 393 | .id_table = pca9541_id, |
| 394 | }; |
| 395 | |
Axel Lin | de05497 | 2012-03-26 21:47:19 +0200 | [diff] [blame] | 396 | module_i2c_driver(pca9541_driver); |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 397 | |
Guenter Roeck | 83a638d | 2012-07-24 14:13:56 +0200 | [diff] [blame] | 398 | MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>"); |
Guenter Roeck | ae63b13 | 2010-10-24 18:16:58 +0200 | [diff] [blame] | 399 | MODULE_DESCRIPTION("PCA9541 I2C master selector driver"); |
| 400 | MODULE_LICENSE("GPL v2"); |