drivers/gpio/gpio-74x164.c

   1 /*
   2  *  74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
   3  *
   4  *  Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
   5  *  Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.com>
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License version 2 as
   9  *  published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/init.h>
  13 #include <linux/mutex.h>
  14 #include <linux/spi/spi.h>
  15 #include <linux/spi/74x164.h>
  16 #include <linux/gpio.h>
  17 #include <linux/of_gpio.h>
  18 #include <linux/slab.h>
  19 #include <linux/module.h>
  20
  21 #define GEN_74X164_NUMBER_GPIOS 8
  22
  23 struct gen_74x164_chip {
  24         struct spi_device       *spi;
  25         u8                      *buffer;
  26         struct gpio_chip        gpio_chip;
  27         struct mutex            lock;
  28         u32                     registers;
  29 };
  30
  31 static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc)
  32 {
  33         return container_of(gc, struct gen_74x164_chip, gpio_chip);
  34 }
  35
  36 static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
  37 {
  38         struct spi_message message;
  39         struct spi_transfer *msg_buf;
  40         int i, ret = 0;
  41
  42         msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer),
  43                         GFP_KERNEL);
  44         if (!msg_buf)
  45                 return -ENOMEM;
  46
  47         spi_message_init(&message);
  48
  49         /*
  50          * Since the registers are chained, every byte sent will make
  51          * the previous byte shift to the next register in the
  52          * chain. Thus, the first byte send will end up in the last
  53          * register at the end of the transfer. So, to have a logical
  54          * numbering, send the bytes in reverse order so that the last
  55          * byte of the buffer will end up in the last register.
  56          */
  57         for (i = chip->registers - 1; i >= 0; i--) {
  58                 msg_buf[i].tx_buf = chip->buffer +i;
  59                 msg_buf[i].len = sizeof(u8);
  60                 spi_message_add_tail(msg_buf + i, &message);
  61         }
  62
  63         ret = spi_sync(chip->spi, &message);
  64
  65         kfree(msg_buf);
  66
  67         return ret;
  68 }
  69
  70 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
  71 {
  72         struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
  73         u8 bank = offset / 8;
  74         u8 pin = offset % 8;
  75         int ret;
  76
  77         mutex_lock(&chip->lock);
  78         ret = (chip->buffer[bank] >> pin) & 0x1;
  79         mutex_unlock(&chip->lock);
  80
  81         return ret;
  82 }
  83
  84 static void gen_74x164_set_value(struct gpio_chip *gc,
  85                 unsigned offset, int val)
  86 {
  87         struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
  88         u8 bank = offset / 8;
  89         u8 pin = offset % 8;
  90
  91         mutex_lock(&chip->lock);
  92         if (val)
  93                 chip->buffer[bank] |= (1 << pin);
  94         else
  95                 chip->buffer[bank] &= ~(1 << pin);
  96
  97         __gen_74x164_write_config(chip);
  98         mutex_unlock(&chip->lock);
  99 }
 100
 101 static int gen_74x164_direction_output(struct gpio_chip *gc,
 102                 unsigned offset, int val)
 103 {
 104         gen_74x164_set_value(gc, offset, val);
 105         return 0;
 106 }
 107
 108 static int gen_74x164_probe(struct spi_device *spi)
 109 {
 110         struct gen_74x164_chip *chip;
 111         struct gen_74x164_chip_platform_data *pdata;
 112         int ret;
 113
 114         if (!spi->dev.of_node) {
 115                 dev_err(&spi->dev, "No device tree data available.\n");
 116                 return -EINVAL;
 117         }
 118
 119         /*
 120          * bits_per_word cannot be configured in platform data
 121          */
 122         spi->bits_per_word = 8;
 123
 124         ret = spi_setup(spi);
 125         if (ret < 0)
 126                 return ret;
 127
 128         chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
 129         if (!chip)
 130                 return -ENOMEM;
 131
 132         pdata = spi->dev.platform_data;
 133         if (pdata && pdata->base)
 134                 chip->gpio_chip.base = pdata->base;
 135         else
 136                 chip->gpio_chip.base = -1;
 137
 138         mutex_init(&chip->lock);
 139
 140         dev_set_drvdata(&spi->dev, chip);
 141
 142         chip->spi = spi;
 143
 144         chip->gpio_chip.label = spi->modalias;
 145         chip->gpio_chip.direction_output = gen_74x164_direction_output;
 146         chip->gpio_chip.get = gen_74x164_get_value;
 147         chip->gpio_chip.set = gen_74x164_set_value;
 148
 149         if (of_property_read_u32(spi->dev.of_node, "registers-number", &chip->registers)) {
 150                 dev_err(&spi->dev, "Missing registers-number property in the DT.\n");
 151                 ret = -EINVAL;
 152                 goto exit_destroy;
 153         }
 154
 155         chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
 156         chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL);
 157         if (!chip->buffer) {
 158                 ret = -ENOMEM;
 159                 goto exit_destroy;
 160         }
 161
 162         chip->gpio_chip.can_sleep = 1;
 163         chip->gpio_chip.dev = &spi->dev;
 164         chip->gpio_chip.owner = THIS_MODULE;
 165
 166         ret = __gen_74x164_write_config(chip);
 167         if (ret) {
 168                 dev_err(&spi->dev, "Failed writing: %d\n", ret);
 169                 goto exit_destroy;
 170         }
 171
 172         ret = gpiochip_add(&chip->gpio_chip);
 173         if (ret)
 174                 goto exit_destroy;
 175
 176         return ret;
 177
 178 exit_destroy:
 179         dev_set_drvdata(&spi->dev, NULL);
 180         mutex_destroy(&chip->lock);
 181         return ret;
 182 }
 183
 184 static int gen_74x164_remove(struct spi_device *spi)
 185 {
 186         struct gen_74x164_chip *chip;
 187         int ret;
 188
 189         chip = dev_get_drvdata(&spi->dev);
 190         if (chip == NULL)
 191                 return -ENODEV;
 192
 193         dev_set_drvdata(&spi->dev, NULL);
 194
 195         ret = gpiochip_remove(&chip->gpio_chip);
 196         if (!ret)
 197                 mutex_destroy(&chip->lock);
 198         else
 199                 dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
 200                                 ret);
 201
 202         return ret;
 203 }
 204
 205 static const struct of_device_id gen_74x164_dt_ids[] = {
 206         { .compatible = "fairchild,74hc595" },
 207         {},
 208 };
 209 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);
 210
 211 static struct spi_driver gen_74x164_driver = {
 212         .driver = {
 213                 .name           = "74x164",
 214                 .owner          = THIS_MODULE,
 215                 .of_match_table = of_match_ptr(gen_74x164_dt_ids),
 216         },
 217         .probe          = gen_74x164_probe,
 218         .remove         = gen_74x164_remove,
 219 };
 220 module_spi_driver(gen_74x164_driver);
 221
 222 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
 223 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
 224 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
 225 MODULE_LICENSE("GPL v2");