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/gpio.h>
  16 #include <linux/of_gpio.h>
  17 #include <linux/slab.h>
  18 #include <linux/module.h>
  19
  20 #define GEN_74X164_NUMBER_GPIOS 8
  21
  22 struct gen_74x164_chip {
  23         u8                      *buffer;
  24         struct gpio_chip        gpio_chip;
  25         struct mutex            lock;
  26         u32                     registers;
  27 };
  28
  29 static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc)
  30 {
  31         return container_of(gc, struct gen_74x164_chip, gpio_chip);
  32 }
  33
  34 static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
  35 {
  36         struct spi_device *spi = to_spi_device(chip->gpio_chip.dev);
  37         struct spi_message message;
  38         struct spi_transfer *msg_buf;
  39         int i, ret = 0;
  40
  41         msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer),
  42                         GFP_KERNEL);
  43         if (!msg_buf)
  44                 return -ENOMEM;
  45
  46         spi_message_init(&message);
  47
  48         /*
  49          * Since the registers are chained, every byte sent will make
  50          * the previous byte shift to the next register in the
  51          * chain. Thus, the first byte send will end up in the last
  52          * register at the end of the transfer. So, to have a logical
  53          * numbering, send the bytes in reverse order so that the last
  54          * byte of the buffer will end up in the last register.
  55          */
  56         for (i = chip->registers - 1; i >= 0; i--) {
  57                 msg_buf[i].tx_buf = chip->buffer + i;
  58                 msg_buf[i].len = sizeof(u8);
  59                 spi_message_add_tail(msg_buf + i, &message);
  60         }
  61
  62         ret = spi_sync(spi, &message);
  63
  64         kfree(msg_buf);
  65
  66         return ret;
  67 }
  68
  69 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
  70 {
  71         struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
  72         u8 bank = offset / 8;
  73         u8 pin = offset % 8;
  74         int ret;
  75
  76         mutex_lock(&chip->lock);
  77         ret = (chip->buffer[bank] >> pin) & 0x1;
  78         mutex_unlock(&chip->lock);
  79
  80         return ret;
  81 }
  82
  83 static void gen_74x164_set_value(struct gpio_chip *gc,
  84                 unsigned offset, int val)
  85 {
  86         struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
  87         u8 bank = offset / 8;
  88         u8 pin = offset % 8;
  89
  90         mutex_lock(&chip->lock);
  91         if (val)
  92                 chip->buffer[bank] |= (1 << pin);
  93         else
  94                 chip->buffer[bank] &= ~(1 << pin);
  95
  96         __gen_74x164_write_config(chip);
  97         mutex_unlock(&chip->lock);
  98 }
  99
 100 static int gen_74x164_direction_output(struct gpio_chip *gc,
 101                 unsigned offset, int val)
 102 {
 103         gen_74x164_set_value(gc, offset, val);
 104         return 0;
 105 }
 106
 107 static int gen_74x164_probe(struct spi_device *spi)
 108 {
 109         struct gen_74x164_chip *chip;
 110         int ret;
 111
 112         /*
 113          * bits_per_word cannot be configured in platform data
 114          */
 115         spi->bits_per_word = 8;
 116
 117         ret = spi_setup(spi);
 118         if (ret < 0)
 119                 return ret;
 120
 121         chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
 122         if (!chip)
 123                 return -ENOMEM;
 124
 125         spi_set_drvdata(spi, chip);
 126
 127         chip->gpio_chip.label = spi->modalias;
 128         chip->gpio_chip.direction_output = gen_74x164_direction_output;
 129         chip->gpio_chip.get = gen_74x164_get_value;
 130         chip->gpio_chip.set = gen_74x164_set_value;
 131         chip->gpio_chip.base = -1;
 132
 133         if (of_property_read_u32(spi->dev.of_node, "registers-number",
 134                                  &chip->registers)) {
 135                 dev_err(&spi->dev,
 136                         "Missing registers-number property in the DT.\n");
 137                 return -EINVAL;
 138         }
 139
 140         chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
 141         chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL);
 142         if (!chip->buffer)
 143                 return -ENOMEM;
 144
 145         chip->gpio_chip.can_sleep = true;
 146         chip->gpio_chip.dev = &spi->dev;
 147         chip->gpio_chip.owner = THIS_MODULE;
 148
 149         mutex_init(&chip->lock);
 150
 151         ret = __gen_74x164_write_config(chip);
 152         if (ret) {
 153                 dev_err(&spi->dev, "Failed writing: %d\n", ret);
 154                 goto exit_destroy;
 155         }
 156
 157         ret = gpiochip_add(&chip->gpio_chip);
 158         if (!ret)
 159                 return 0;
 160
 161 exit_destroy:
 162         mutex_destroy(&chip->lock);
 163
 164         return ret;
 165 }
 166
 167 static int gen_74x164_remove(struct spi_device *spi)
 168 {
 169         struct gen_74x164_chip *chip = spi_get_drvdata(spi);
 170         int ret;
 171
 172         ret = gpiochip_remove(&chip->gpio_chip);
 173         if (!ret)
 174                 mutex_destroy(&chip->lock);
 175
 176         return ret;
 177 }
 178
 179 static const struct of_device_id gen_74x164_dt_ids[] = {
 180         { .compatible = "fairchild,74hc595" },
 181         {},
 182 };
 183 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);
 184
 185 static struct spi_driver gen_74x164_driver = {
 186         .driver = {
 187                 .name           = "74x164",
 188                 .owner          = THIS_MODULE,
 189                 .of_match_table = gen_74x164_dt_ids,
 190         },
 191         .probe          = gen_74x164_probe,
 192         .remove         = gen_74x164_remove,
 193 };
 194 module_spi_driver(gen_74x164_driver);
 195
 196 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
 197 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
 198 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
 199 MODULE_LICENSE("GPL v2");