drivers/i2c/muxes/pca954x.c

   1 /*
   2  * I2C multiplexer
   3  *
   4  * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
   5  * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
   6  *
   7  * This module supports the PCA954x series of I2C multiplexer/switch chips
   8  * made by Philips Semiconductors.
   9  * This includes the:
  10  *       PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
  11  *       and PCA9548.
  12  *
  13  * These chips are all controlled via the I2C bus itself, and all have a
  14  * single 8-bit register. The upstream "parent" bus fans out to two,
  15  * four, or eight downstream busses or channels; which of these
  16  * are selected is determined by the chip type and register contents. A
  17  * mux can select only one sub-bus at a time; a switch can select any
  18  * combination simultaneously.
  19  *
  20  * Based on:
  21  *      pca954x.c from Kumar Gala <galak@kernel.crashing.org>
  22  * Copyright (C) 2006
  23  *
  24  * Based on:
  25  *      pca954x.c from Ken Harrenstien
  26  * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
  27  *
  28  * Based on:
  29  *      i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
  30  * and
  31  *      pca9540.c from Jean Delvare <khali@linux-fr.org>.
  32  *
  33  * This file is licensed under the terms of the GNU General Public
  34  * License version 2. This program is licensed "as is" without any
  35  * warranty of any kind, whether express or implied.
  36  */
  37
  38 #include <linux/module.h>
  39 #include <linux/init.h>
  40 #include <linux/slab.h>
  41 #include <linux/device.h>
  42 #include <linux/i2c.h>
  43 #include <linux/i2c-mux.h>
  44
  45 #include <linux/i2c/pca954x.h>
  46
  47 #define PCA954X_MAX_NCHANS 8
  48
  49 enum pca_type {
  50         pca_9540,
  51         pca_9542,
  52         pca_9543,
  53         pca_9544,
  54         pca_9545,
  55         pca_9546,
  56         pca_9547,
  57         pca_9548,
  58 };
  59
  60 struct pca954x {
  61         enum pca_type type;
  62         struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
  63
  64         u8 last_chan;           /* last register value */
  65 };
  66
  67 struct chip_desc {
  68         u8 nchans;
  69         u8 enable;      /* used for muxes only */
  70         enum muxtype {
  71                 pca954x_ismux = 0,
  72                 pca954x_isswi
  73         } muxtype;
  74 };
  75
  76 /* Provide specs for the PCA954x types we know about */
  77 static const struct chip_desc chips[] = {
  78         [pca_9540] = {
  79                 .nchans = 2,
  80                 .enable = 0x4,
  81                 .muxtype = pca954x_ismux,
  82         },
  83         [pca_9543] = {
  84                 .nchans = 2,
  85                 .muxtype = pca954x_isswi,
  86         },
  87         [pca_9544] = {
  88                 .nchans = 4,
  89                 .enable = 0x4,
  90                 .muxtype = pca954x_ismux,
  91         },
  92         [pca_9545] = {
  93                 .nchans = 4,
  94                 .muxtype = pca954x_isswi,
  95         },
  96         [pca_9547] = {
  97                 .nchans = 8,
  98                 .enable = 0x8,
  99                 .muxtype = pca954x_ismux,
 100         },
 101         [pca_9548] = {
 102                 .nchans = 8,
 103                 .muxtype = pca954x_isswi,
 104         },
 105 };
 106
 107 static const struct i2c_device_id pca954x_id[] = {
 108         { "pca9540", pca_9540 },
 109         { "pca9542", pca_9540 },
 110         { "pca9543", pca_9543 },
 111         { "pca9544", pca_9544 },
 112         { "pca9545", pca_9545 },
 113         { "pca9546", pca_9545 },
 114         { "pca9547", pca_9547 },
 115         { "pca9548", pca_9548 },
 116         { }
 117 };
 118 MODULE_DEVICE_TABLE(i2c, pca954x_id);
 119
 120 /* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
 121    for this as they will try to lock adapter a second time */
 122 static int pca954x_reg_write(struct i2c_adapter *adap,
 123                              struct i2c_client *client, u8 val)
 124 {
 125         int ret = -ENODEV;
 126
 127         if (adap->algo->master_xfer) {
 128                 struct i2c_msg msg;
 129                 char buf[1];
 130
 131                 msg.addr = client->addr;
 132                 msg.flags = 0;
 133                 msg.len = 1;
 134                 buf[0] = val;
 135                 msg.buf = buf;
 136                 ret = adap->algo->master_xfer(adap, &msg, 1);
 137         } else {
 138                 union i2c_smbus_data data;
 139                 ret = adap->algo->smbus_xfer(adap, client->addr,
 140                                              client->flags,
 141                                              I2C_SMBUS_WRITE,
 142                                              val, I2C_SMBUS_BYTE, &data);
 143         }
 144
 145         return ret;
 146 }
 147
 148 static int pca954x_select_chan(struct i2c_adapter *adap,
 149                                void *client, u32 chan)
 150 {
 151         struct pca954x *data = i2c_get_clientdata(client);
 152         const struct chip_desc *chip = &chips[data->type];
 153         u8 regval;
 154         int ret = 0;
 155
 156         /* we make switches look like muxes, not sure how to be smarter */
 157         if (chip->muxtype == pca954x_ismux)
 158                 regval = chan | chip->enable;
 159         else
 160                 regval = 1 << chan;
 161
 162         /* Only select the channel if its different from the last channel */
 163         if (data->last_chan != regval) {
 164                 ret = pca954x_reg_write(adap, client, regval);
 165                 data->last_chan = regval;
 166         }
 167
 168         return ret;
 169 }
 170
 171 static int pca954x_deselect_mux(struct i2c_adapter *adap,
 172                                 void *client, u32 chan)
 173 {
 174         struct pca954x *data = i2c_get_clientdata(client);
 175
 176         /* Deselect active channel */
 177         data->last_chan = 0;
 178         return pca954x_reg_write(adap, client, data->last_chan);
 179 }
 180
 181 /*
 182  * I2C init/probing/exit functions
 183  */
 184 static int pca954x_probe(struct i2c_client *client,
 185                          const struct i2c_device_id *id)
 186 {
 187         struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
 188         struct pca954x_platform_data *pdata = client->dev.platform_data;
 189         int num, force;
 190         struct pca954x *data;
 191         int ret = -ENODEV;
 192
 193         if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
 194                 goto err;
 195
 196         data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
 197         if (!data) {
 198                 ret = -ENOMEM;
 199                 goto err;
 200         }
 201
 202         i2c_set_clientdata(client, data);
 203
 204         /* Write the mux register at addr to verify
 205          * that the mux is in fact present. This also
 206          * initializes the mux to disconnected state.
 207          */
 208         if (i2c_smbus_write_byte(client, 0) < 0) {
 209                 dev_warn(&client->dev, "probe failed\n");
 210                 goto exit_free;
 211         }
 212
 213         data->type = id->driver_data;
 214         data->last_chan = 0;               /* force the first selection */
 215
 216         /* Now create an adapter for each channel */
 217         for (num = 0; num < chips[data->type].nchans; num++) {
 218                 force = 0;                        /* dynamic adap number */
 219                 if (pdata) {
 220                         if (num < pdata->num_modes)
 221                                 /* force static number */
 222                                 force = pdata->modes[num].adap_id;
 223                         else
 224                                 /* discard unconfigured channels */
 225                                 break;
 226                 }
 227
 228                 data->virt_adaps[num] =
 229                         i2c_add_mux_adapter(adap, client,
 230                                 force, num, pca954x_select_chan,
 231                                 (pdata && pdata->modes[num].deselect_on_exit)
 232                                         ? pca954x_deselect_mux : NULL);
 233
 234                 if (data->virt_adaps[num] == NULL) {
 235                         ret = -ENODEV;
 236                         dev_err(&client->dev,
 237                                 "failed to register multiplexed adapter"
 238                                 " %d as bus %d\n", num, force);
 239                         goto virt_reg_failed;
 240                 }
 241         }
 242
 243         dev_info(&client->dev,
 244                  "registered %d multiplexed busses for I2C %s %s\n",
 245                  num, chips[data->type].muxtype == pca954x_ismux
 246                                 ? "mux" : "switch", client->name);
 247
 248         return 0;
 249
 250 virt_reg_failed:
 251         for (num--; num >= 0; num--)
 252                 i2c_del_mux_adapter(data->virt_adaps[num]);
 253 exit_free:
 254         kfree(data);
 255 err:
 256         return ret;
 257 }
 258
 259 static int pca954x_remove(struct i2c_client *client)
 260 {
 261         struct pca954x *data = i2c_get_clientdata(client);
 262         const struct chip_desc *chip = &chips[data->type];
 263         int i, err;
 264
 265         for (i = 0; i < chip->nchans; ++i)
 266                 if (data->virt_adaps[i]) {
 267                         err = i2c_del_mux_adapter(data->virt_adaps[i]);
 268                         if (err)
 269                                 return err;
 270                         data->virt_adaps[i] = NULL;
 271                 }
 272
 273         kfree(data);
 274         return 0;
 275 }
 276
 277 static struct i2c_driver pca954x_driver = {
 278         .driver         = {
 279                 .name   = "pca954x",
 280                 .owner  = THIS_MODULE,
 281         },
 282         .probe          = pca954x_probe,
 283         .remove         = pca954x_remove,
 284         .id_table       = pca954x_id,
 285 };
 286
 287 static int __init pca954x_init(void)
 288 {
 289         return i2c_add_driver(&pca954x_driver);
 290 }
 291
 292 static void __exit pca954x_exit(void)
 293 {
 294         i2c_del_driver(&pca954x_driver);
 295 }
 296
 297 module_init(pca954x_init);
 298 module_exit(pca954x_exit);
 299
 300 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 301 MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
 302 MODULE_LICENSE("GPL v2");