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         return spi_write(to_spi_device(chip->gpio_chip.parent), chip->buffer,
  39                          chip->registers);
  40 }
  41
  42 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
  43 {
  44         struct gen_74x164_chip *chip = gpiochip_get_data(gc);
  45         u8 bank = chip->registers - 1 - offset / 8;
  46         u8 pin = offset % 8;
  47         int ret;
  48
  49         mutex_lock(&chip->lock);
  50         ret = (chip->buffer[bank] >> pin) & 0x1;
  51         mutex_unlock(&chip->lock);
  52
  53         return ret;
  54 }
  55
  56 static void gen_74x164_set_value(struct gpio_chip *gc,
  57                 unsigned offset, int val)
  58 {
  59         struct gen_74x164_chip *chip = gpiochip_get_data(gc);
  60         u8 bank = chip->registers - 1 - offset / 8;
  61         u8 pin = offset % 8;
  62
  63         mutex_lock(&chip->lock);
  64         if (val)
  65                 chip->buffer[bank] |= (1 << pin);
  66         else
  67                 chip->buffer[bank] &= ~(1 << pin);
  68
  69         __gen_74x164_write_config(chip);
  70         mutex_unlock(&chip->lock);
  71 }
  72
  73 static void gen_74x164_set_multiple(struct gpio_chip *gc, unsigned long *mask,
  74                                     unsigned long *bits)
  75 {
  76         struct gen_74x164_chip *chip = gpiochip_get_data(gc);
  77         unsigned int i, idx, shift;
  78         u8 bank, bankmask;
  79
  80         mutex_lock(&chip->lock);
  81         for (i = 0, bank = chip->registers - 1; i < chip->registers;
  82              i++, bank--) {
  83                 idx = i / sizeof(*mask);
  84                 shift = i % sizeof(*mask) * BITS_PER_BYTE;
  85                 bankmask = mask[idx] >> shift;
  86                 if (!bankmask)
  87                         continue;
  88
  89                 chip->buffer[bank] &= ~bankmask;
  90                 chip->buffer[bank] |= bankmask & (bits[idx] >> shift);
  91         }
  92         __gen_74x164_write_config(chip);
  93         mutex_unlock(&chip->lock);
  94 }
  95
  96 static int gen_74x164_direction_output(struct gpio_chip *gc,
  97                 unsigned offset, int val)
  98 {
  99         gen_74x164_set_value(gc, offset, val);
 100         return 0;
 101 }
 102
 103 static int gen_74x164_probe(struct spi_device *spi)
 104 {
 105         struct gen_74x164_chip *chip;
 106         u32 nregs;
 107         int ret;
 108
 109         /*
 110          * bits_per_word cannot be configured in platform data
 111          */
 112         spi->bits_per_word = 8;
 113
 114         ret = spi_setup(spi);
 115         if (ret < 0)
 116                 return ret;
 117
 118         if (of_property_read_u32(spi->dev.of_node, "registers-number",
 119                                  &nregs)) {
 120                 dev_err(&spi->dev,
 121                         "Missing registers-number property in the DT.\n");
 122                 return -EINVAL;
 123         }
 124
 125         chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL);
 126         if (!chip)
 127                 return -ENOMEM;
 128
 129         spi_set_drvdata(spi, chip);
 130
 131         chip->gpio_chip.label = spi->modalias;
 132         chip->gpio_chip.direction_output = gen_74x164_direction_output;
 133         chip->gpio_chip.get = gen_74x164_get_value;
 134         chip->gpio_chip.set = gen_74x164_set_value;
 135         chip->gpio_chip.set_multiple = gen_74x164_set_multiple;
 136         chip->gpio_chip.base = -1;
 137
 138         chip->registers = nregs;
 139         chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
 140
 141         chip->gpio_chip.can_sleep = true;
 142         chip->gpio_chip.parent = &spi->dev;
 143         chip->gpio_chip.owner = THIS_MODULE;
 144
 145         mutex_init(&chip->lock);
 146
 147         ret = __gen_74x164_write_config(chip);
 148         if (ret) {
 149                 dev_err(&spi->dev, "Failed writing: %d\n", ret);
 150                 goto exit_destroy;
 151         }
 152
 153         ret = gpiochip_add_data(&chip->gpio_chip, chip);
 154         if (!ret)
 155                 return 0;
 156
 157 exit_destroy:
 158         mutex_destroy(&chip->lock);
 159
 160         return ret;
 161 }
 162
 163 static int gen_74x164_remove(struct spi_device *spi)
 164 {
 165         struct gen_74x164_chip *chip = spi_get_drvdata(spi);
 166
 167         gpiochip_remove(&chip->gpio_chip);
 168         mutex_destroy(&chip->lock);
 169
 170         return 0;
 171 }
 172
 173 static const struct of_device_id gen_74x164_dt_ids[] = {
 174         { .compatible = "fairchild,74hc595" },
 175         { .compatible = "nxp,74lvc594" },
 176         {},
 177 };
 178 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);
 179
 180 static struct spi_driver gen_74x164_driver = {
 181         .driver = {
 182                 .name           = "74x164",
 183                 .of_match_table = gen_74x164_dt_ids,
 184         },
 185         .probe          = gen_74x164_probe,
 186         .remove         = gen_74x164_remove,
 187 };
 188 module_spi_driver(gen_74x164_driver);
 189
 190 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
 191 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
 192 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
 193 MODULE_LICENSE("GPL v2");