linux/drivers/i2c/muxes/i2c-mux-pca954x.c
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   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
  49enum 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
  60struct 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
  67struct 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 */
  77static 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
 107static 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};
 118MODULE_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 */
 122static 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
 148static 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
 171static 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 */
 184static 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, class;
 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                class = 0;                        /* no class by default */
 220                if (pdata) {
 221                        if (num < pdata->num_modes) {
 222                                /* force static number */
 223                                force = pdata->modes[num].adap_id;
 224                                class = pdata->modes[num].class;
 225                        } else
 226                                /* discard unconfigured channels */
 227                                break;
 228                }
 229
 230                data->virt_adaps[num] =
 231                        i2c_add_mux_adapter(adap, &client->dev, client,
 232                                force, num, class, pca954x_select_chan,
 233                                (pdata && pdata->modes[num].deselect_on_exit)
 234                                        ? pca954x_deselect_mux : NULL);
 235
 236                if (data->virt_adaps[num] == NULL) {
 237                        ret = -ENODEV;
 238                        dev_err(&client->dev,
 239                                "failed to register multiplexed adapter"
 240                                " %d as bus %d\n", num, force);
 241                        goto virt_reg_failed;
 242                }
 243        }
 244
 245        dev_info(&client->dev,
 246                 "registered %d multiplexed busses for I2C %s %s\n",
 247                 num, chips[data->type].muxtype == pca954x_ismux
 248                                ? "mux" : "switch", client->name);
 249
 250        return 0;
 251
 252virt_reg_failed:
 253        for (num--; num >= 0; num--)
 254                i2c_del_mux_adapter(data->virt_adaps[num]);
 255exit_free:
 256        kfree(data);
 257err:
 258        return ret;
 259}
 260
 261static int pca954x_remove(struct i2c_client *client)
 262{
 263        struct pca954x *data = i2c_get_clientdata(client);
 264        const struct chip_desc *chip = &chips[data->type];
 265        int i, err;
 266
 267        for (i = 0; i < chip->nchans; ++i)
 268                if (data->virt_adaps[i]) {
 269                        err = i2c_del_mux_adapter(data->virt_adaps[i]);
 270                        if (err)
 271                                return err;
 272                        data->virt_adaps[i] = NULL;
 273                }
 274
 275        kfree(data);
 276        return 0;
 277}
 278
 279static struct i2c_driver pca954x_driver = {
 280        .driver         = {
 281                .name   = "pca954x",
 282                .owner  = THIS_MODULE,
 283        },
 284        .probe          = pca954x_probe,
 285        .remove         = pca954x_remove,
 286        .id_table       = pca954x_id,
 287};
 288
 289module_i2c_driver(pca954x_driver);
 290
 291MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 292MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
 293MODULE_LICENSE("GPL v2");
 294