drivers/i2c/busses/i2c-cbus-gpio.c

   1 /*
   2  * CBUS I2C driver for Nokia Internet Tablets.
   3  *
   4  * Copyright (C) 2004-2010 Nokia Corporation
   5  *
   6  * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
   7  * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
   8  *
   9  * This file is subject to the terms and conditions of the GNU General
  10  * Public License. See the file "COPYING" in the main directory of this
  11  * archive for more details.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/io.h>
  20 #include <linux/i2c.h>
  21 #include <linux/gpio.h>
  22 #include <linux/init.h>
  23 #include <linux/slab.h>
  24 #include <linux/delay.h>
  25 #include <linux/errno.h>
  26 #include <linux/kernel.h>
  27 #include <linux/module.h>
  28 #include <linux/of_gpio.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/platform_data/i2c-cbus-gpio.h>
  32
  33 /*
  34  * Bit counts are derived from Nokia implementation. These should be checked
  35  * if other CBUS implementations appear.
  36  */
  37 #define CBUS_ADDR_BITS  3
  38 #define CBUS_REG_BITS   5
  39
  40 struct cbus_host {
  41         spinlock_t      lock;           /* host lock */
  42         struct device   *dev;
  43         int             clk_gpio;
  44         int             dat_gpio;
  45         int             sel_gpio;
  46 };
  47
  48 /**
  49  * cbus_send_bit - sends one bit over the bus
  50  * @host: the host we're using
  51  * @bit: one bit of information to send
  52  */
  53 static void cbus_send_bit(struct cbus_host *host, unsigned bit)
  54 {
  55         gpio_set_value(host->dat_gpio, bit ? 1 : 0);
  56         gpio_set_value(host->clk_gpio, 1);
  57         gpio_set_value(host->clk_gpio, 0);
  58 }
  59
  60 /**
  61  * cbus_send_data - sends @len amount of data over the bus
  62  * @host: the host we're using
  63  * @data: the data to send
  64  * @len: size of the transfer
  65  */
  66 static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)
  67 {
  68         int i;
  69
  70         for (i = len; i > 0; i--)
  71                 cbus_send_bit(host, data & (1 << (i - 1)));
  72 }
  73
  74 /**
  75  * cbus_receive_bit - receives one bit from the bus
  76  * @host: the host we're using
  77  */
  78 static int cbus_receive_bit(struct cbus_host *host)
  79 {
  80         int ret;
  81
  82         gpio_set_value(host->clk_gpio, 1);
  83         ret = gpio_get_value(host->dat_gpio);
  84         gpio_set_value(host->clk_gpio, 0);
  85         return ret;
  86 }
  87
  88 /**
  89  * cbus_receive_word - receives 16-bit word from the bus
  90  * @host: the host we're using
  91  */
  92 static int cbus_receive_word(struct cbus_host *host)
  93 {
  94         int ret = 0;
  95         int i;
  96
  97         for (i = 16; i > 0; i--) {
  98                 int bit = cbus_receive_bit(host);
  99
 100                 if (bit < 0)
 101                         return bit;
 102
 103                 if (bit)
 104                         ret |= 1 << (i - 1);
 105         }
 106         return ret;
 107 }
 108
 109 /**
 110  * cbus_transfer - transfers data over the bus
 111  * @host: the host we're using
 112  * @rw: read/write flag
 113  * @dev: device address
 114  * @reg: register address
 115  * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
 116  */
 117 static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
 118                          unsigned reg, unsigned data)
 119 {
 120         unsigned long flags;
 121         int ret;
 122
 123         /* We don't want interrupts disturbing our transfer */
 124         spin_lock_irqsave(&host->lock, flags);
 125
 126         /* Reset state and start of transfer, SEL stays down during transfer */
 127         gpio_set_value(host->sel_gpio, 0);
 128
 129         /* Set the DAT pin to output */
 130         gpio_direction_output(host->dat_gpio, 1);
 131
 132         /* Send the device address */
 133         cbus_send_data(host, dev, CBUS_ADDR_BITS);
 134
 135         /* Send the rw flag */
 136         cbus_send_bit(host, rw == I2C_SMBUS_READ);
 137
 138         /* Send the register address */
 139         cbus_send_data(host, reg, CBUS_REG_BITS);
 140
 141         if (rw == I2C_SMBUS_WRITE) {
 142                 cbus_send_data(host, data, 16);
 143                 ret = 0;
 144         } else {
 145                 ret = gpio_direction_input(host->dat_gpio);
 146                 if (ret) {
 147                         dev_dbg(host->dev, "failed setting direction\n");
 148                         goto out;
 149                 }
 150                 gpio_set_value(host->clk_gpio, 1);
 151
 152                 ret = cbus_receive_word(host);
 153                 if (ret < 0) {
 154                         dev_dbg(host->dev, "failed receiving data\n");
 155                         goto out;
 156                 }
 157         }
 158
 159         /* Indicate end of transfer, SEL goes up until next transfer */
 160         gpio_set_value(host->sel_gpio, 1);
 161         gpio_set_value(host->clk_gpio, 1);
 162         gpio_set_value(host->clk_gpio, 0);
 163
 164 out:
 165         spin_unlock_irqrestore(&host->lock, flags);
 166
 167         return ret;
 168 }
 169
 170 static int cbus_i2c_smbus_xfer(struct i2c_adapter       *adapter,
 171                                u16                      addr,
 172                                unsigned short           flags,
 173                                char                     read_write,
 174                                u8                       command,
 175                                int                      size,
 176                                union i2c_smbus_data     *data)
 177 {
 178         struct cbus_host *chost = i2c_get_adapdata(adapter);
 179         int ret;
 180
 181         if (size != I2C_SMBUS_WORD_DATA)
 182                 return -EINVAL;
 183
 184         ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,
 185                             command, data->word);
 186         if (ret < 0)
 187                 return ret;
 188
 189         if (read_write == I2C_SMBUS_READ)
 190                 data->word = ret;
 191
 192         return 0;
 193 }
 194
 195 static u32 cbus_i2c_func(struct i2c_adapter *adapter)
 196 {
 197         return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;
 198 }
 199
 200 static const struct i2c_algorithm cbus_i2c_algo = {
 201         .smbus_xfer     = cbus_i2c_smbus_xfer,
 202         .functionality  = cbus_i2c_func,
 203 };
 204
 205 static int cbus_i2c_remove(struct platform_device *pdev)
 206 {
 207         struct i2c_adapter *adapter = platform_get_drvdata(pdev);
 208
 209         i2c_del_adapter(adapter);
 210
 211         return 0;
 212 }
 213
 214 static int cbus_i2c_probe(struct platform_device *pdev)
 215 {
 216         struct i2c_adapter *adapter;
 217         struct cbus_host *chost;
 218         int ret;
 219
 220         adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),
 221                                GFP_KERNEL);
 222         if (!adapter)
 223                 return -ENOMEM;
 224
 225         chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);
 226         if (!chost)
 227                 return -ENOMEM;
 228
 229         if (pdev->dev.of_node) {
 230                 struct device_node *dnode = pdev->dev.of_node;
 231                 if (of_gpio_count(dnode) != 3)
 232                         return -ENODEV;
 233                 chost->clk_gpio = of_get_gpio(dnode, 0);
 234                 chost->dat_gpio = of_get_gpio(dnode, 1);
 235                 chost->sel_gpio = of_get_gpio(dnode, 2);
 236         } else if (pdev->dev.platform_data) {
 237                 struct i2c_cbus_platform_data *pdata = pdev->dev.platform_data;
 238                 chost->clk_gpio = pdata->clk_gpio;
 239                 chost->dat_gpio = pdata->dat_gpio;
 240                 chost->sel_gpio = pdata->sel_gpio;
 241         } else {
 242                 return -ENODEV;
 243         }
 244
 245         adapter->owner          = THIS_MODULE;
 246         adapter->class          = I2C_CLASS_HWMON;
 247         adapter->dev.parent     = &pdev->dev;
 248         adapter->nr             = pdev->id;
 249         adapter->timeout        = HZ;
 250         adapter->algo           = &cbus_i2c_algo;
 251         strlcpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));
 252
 253         spin_lock_init(&chost->lock);
 254         chost->dev = &pdev->dev;
 255
 256         ret = devm_gpio_request_one(&pdev->dev, chost->clk_gpio,
 257                                     GPIOF_OUT_INIT_LOW, "CBUS clk");
 258         if (ret)
 259                 return ret;
 260
 261         ret = devm_gpio_request_one(&pdev->dev, chost->dat_gpio, GPIOF_IN,
 262                                     "CBUS data");
 263         if (ret)
 264                 return ret;
 265
 266         ret = devm_gpio_request_one(&pdev->dev, chost->sel_gpio,
 267                                     GPIOF_OUT_INIT_HIGH, "CBUS sel");
 268         if (ret)
 269                 return ret;
 270
 271         i2c_set_adapdata(adapter, chost);
 272         platform_set_drvdata(pdev, adapter);
 273
 274         return i2c_add_numbered_adapter(adapter);
 275 }
 276
 277 #if defined(CONFIG_OF)
 278 static const struct of_device_id i2c_cbus_dt_ids[] = {
 279         { .compatible = "i2c-cbus-gpio", },
 280         { }
 281 };
 282 MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);
 283 #endif
 284
 285 static struct platform_driver cbus_i2c_driver = {
 286         .probe  = cbus_i2c_probe,
 287         .remove = cbus_i2c_remove,
 288         .driver = {
 289                 .owner  = THIS_MODULE,
 290                 .name   = "i2c-cbus-gpio",
 291         },
 292 };
 293 module_platform_driver(cbus_i2c_driver);
 294
 295 MODULE_ALIAS("platform:i2c-cbus-gpio");
 296 MODULE_DESCRIPTION("CBUS I2C driver");
 297 MODULE_AUTHOR("Juha Yrjölä");
 298 MODULE_AUTHOR("David Weinehall");
 299 MODULE_AUTHOR("Mikko Ylinen");
 300 MODULE_AUTHOR("Felipe Balbi");
 301 MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");
 302 MODULE_LICENSE("GPL");