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/slab.h>
  22 #include <linux/delay.h>
  23 #include <linux/errno.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/gpio/consumer.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/platform_device.h>
  29
  30 /*
  31  * Bit counts are derived from Nokia implementation. These should be checked
  32  * if other CBUS implementations appear.
  33  */
  34 #define CBUS_ADDR_BITS  3
  35 #define CBUS_REG_BITS   5
  36
  37 struct cbus_host {
  38         spinlock_t      lock;           /* host lock */
  39         struct device   *dev;
  40         struct gpio_desc *clk;
  41         struct gpio_desc *dat;
  42         struct gpio_desc *sel;
  43 };
  44
  45 /**
  46  * cbus_send_bit - sends one bit over the bus
  47  * @host: the host we're using
  48  * @bit: one bit of information to send
  49  */
  50 static void cbus_send_bit(struct cbus_host *host, unsigned bit)
  51 {
  52         gpiod_set_value(host->dat, bit ? 1 : 0);
  53         gpiod_set_value(host->clk, 1);
  54         gpiod_set_value(host->clk, 0);
  55 }
  56
  57 /**
  58  * cbus_send_data - sends @len amount of data over the bus
  59  * @host: the host we're using
  60  * @data: the data to send
  61  * @len: size of the transfer
  62  */
  63 static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)
  64 {
  65         int i;
  66
  67         for (i = len; i > 0; i--)
  68                 cbus_send_bit(host, data & (1 << (i - 1)));
  69 }
  70
  71 /**
  72  * cbus_receive_bit - receives one bit from the bus
  73  * @host: the host we're using
  74  */
  75 static int cbus_receive_bit(struct cbus_host *host)
  76 {
  77         int ret;
  78
  79         gpiod_set_value(host->clk, 1);
  80         ret = gpiod_get_value(host->dat);
  81         gpiod_set_value(host->clk, 0);
  82         return ret;
  83 }
  84
  85 /**
  86  * cbus_receive_word - receives 16-bit word from the bus
  87  * @host: the host we're using
  88  */
  89 static int cbus_receive_word(struct cbus_host *host)
  90 {
  91         int ret = 0;
  92         int i;
  93
  94         for (i = 16; i > 0; i--) {
  95                 int bit = cbus_receive_bit(host);
  96
  97                 if (bit < 0)
  98                         return bit;
  99
 100                 if (bit)
 101                         ret |= 1 << (i - 1);
 102         }
 103         return ret;
 104 }
 105
 106 /**
 107  * cbus_transfer - transfers data over the bus
 108  * @host: the host we're using
 109  * @rw: read/write flag
 110  * @dev: device address
 111  * @reg: register address
 112  * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
 113  */
 114 static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
 115                          unsigned reg, unsigned data)
 116 {
 117         unsigned long flags;
 118         int ret;
 119
 120         /* We don't want interrupts disturbing our transfer */
 121         spin_lock_irqsave(&host->lock, flags);
 122
 123         /* Reset state and start of transfer, SEL stays down during transfer */
 124         gpiod_set_value(host->sel, 0);
 125
 126         /* Set the DAT pin to output */
 127         gpiod_direction_output(host->dat, 1);
 128
 129         /* Send the device address */
 130         cbus_send_data(host, dev, CBUS_ADDR_BITS);
 131
 132         /* Send the rw flag */
 133         cbus_send_bit(host, rw == I2C_SMBUS_READ);
 134
 135         /* Send the register address */
 136         cbus_send_data(host, reg, CBUS_REG_BITS);
 137
 138         if (rw == I2C_SMBUS_WRITE) {
 139                 cbus_send_data(host, data, 16);
 140                 ret = 0;
 141         } else {
 142                 ret = gpiod_direction_input(host->dat);
 143                 if (ret) {
 144                         dev_dbg(host->dev, "failed setting direction\n");
 145                         goto out;
 146                 }
 147                 gpiod_set_value(host->clk, 1);
 148
 149                 ret = cbus_receive_word(host);
 150                 if (ret < 0) {
 151                         dev_dbg(host->dev, "failed receiving data\n");
 152                         goto out;
 153                 }
 154         }
 155
 156         /* Indicate end of transfer, SEL goes up until next transfer */
 157         gpiod_set_value(host->sel, 1);
 158         gpiod_set_value(host->clk, 1);
 159         gpiod_set_value(host->clk, 0);
 160
 161 out:
 162         spin_unlock_irqrestore(&host->lock, flags);
 163
 164         return ret;
 165 }
 166
 167 static int cbus_i2c_smbus_xfer(struct i2c_adapter       *adapter,
 168                                u16                      addr,
 169                                unsigned short           flags,
 170                                char                     read_write,
 171                                u8                       command,
 172                                int                      size,
 173                                union i2c_smbus_data     *data)
 174 {
 175         struct cbus_host *chost = i2c_get_adapdata(adapter);
 176         int ret;
 177
 178         if (size != I2C_SMBUS_WORD_DATA)
 179                 return -EINVAL;
 180
 181         ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,
 182                             command, data->word);
 183         if (ret < 0)
 184                 return ret;
 185
 186         if (read_write == I2C_SMBUS_READ)
 187                 data->word = ret;
 188
 189         return 0;
 190 }
 191
 192 static u32 cbus_i2c_func(struct i2c_adapter *adapter)
 193 {
 194         return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;
 195 }
 196
 197 static const struct i2c_algorithm cbus_i2c_algo = {
 198         .smbus_xfer             = cbus_i2c_smbus_xfer,
 199         .smbus_xfer_atomic      = cbus_i2c_smbus_xfer,
 200         .functionality          = cbus_i2c_func,
 201 };
 202
 203 static void cbus_i2c_remove(struct platform_device *pdev)
 204 {
 205         struct i2c_adapter *adapter = platform_get_drvdata(pdev);
 206
 207         i2c_del_adapter(adapter);
 208 }
 209
 210 static int cbus_i2c_probe(struct platform_device *pdev)
 211 {
 212         struct i2c_adapter *adapter;
 213         struct cbus_host *chost;
 214
 215         adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),
 216                                GFP_KERNEL);
 217         if (!adapter)
 218                 return -ENOMEM;
 219
 220         chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);
 221         if (!chost)
 222                 return -ENOMEM;
 223
 224         if (gpiod_count(&pdev->dev, NULL) != 3)
 225                 return -ENODEV;
 226         chost->clk = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_LOW);
 227         if (IS_ERR(chost->clk))
 228                 return PTR_ERR(chost->clk);
 229         chost->dat = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_IN);
 230         if (IS_ERR(chost->dat))
 231                 return PTR_ERR(chost->dat);
 232         chost->sel = devm_gpiod_get_index(&pdev->dev, NULL, 2, GPIOD_OUT_HIGH);
 233         if (IS_ERR(chost->sel))
 234                 return PTR_ERR(chost->sel);
 235         gpiod_set_consumer_name(chost->clk, "CBUS clk");
 236         gpiod_set_consumer_name(chost->dat, "CBUS dat");
 237         gpiod_set_consumer_name(chost->sel, "CBUS sel");
 238
 239         adapter->owner          = THIS_MODULE;
 240         adapter->class          = I2C_CLASS_HWMON;
 241         adapter->dev.parent     = &pdev->dev;
 242         adapter->dev.of_node    = pdev->dev.of_node;
 243         adapter->nr             = pdev->id;
 244         adapter->timeout        = HZ;
 245         adapter->algo           = &cbus_i2c_algo;
 246         strscpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));
 247
 248         spin_lock_init(&chost->lock);
 249         chost->dev = &pdev->dev;
 250
 251         i2c_set_adapdata(adapter, chost);
 252         platform_set_drvdata(pdev, adapter);
 253
 254         return i2c_add_numbered_adapter(adapter);
 255 }
 256
 257 #if defined(CONFIG_OF)
 258 static const struct of_device_id i2c_cbus_dt_ids[] = {
 259         { .compatible = "i2c-cbus-gpio", },
 260         { }
 261 };
 262 MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);
 263 #endif
 264
 265 static struct platform_driver cbus_i2c_driver = {
 266         .probe  = cbus_i2c_probe,
 267         .remove = cbus_i2c_remove,
 268         .driver = {
 269                 .name   = "i2c-cbus-gpio",
 270                 .of_match_table = of_match_ptr(i2c_cbus_dt_ids),
 271         },
 272 };
 273 module_platform_driver(cbus_i2c_driver);
 274
 275 MODULE_ALIAS("platform:i2c-cbus-gpio");
 276 MODULE_DESCRIPTION("CBUS I2C driver");
 277 MODULE_AUTHOR("Juha Yrjölä");
 278 MODULE_AUTHOR("David Weinehall");
 279 MODULE_AUTHOR("Mikko Ylinen");
 280 MODULE_AUTHOR("Felipe Balbi");
 281 MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");
 282 MODULE_LICENSE("GPL");