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