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 struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc) 37 { 38 return container_of(gc, struct gen_74x164_chip, gpio_chip); 39 } 40 41 static int __gen_74x164_write_config(struct gen_74x164_chip *chip) 42 { 43 struct spi_transfer xfer = { 44 .tx_buf = chip->buffer, 45 .len = chip->registers, 46 }; 47 48 return spi_sync_transfer(to_spi_device(chip->gpio_chip.parent), 49 &xfer, 1); 50 } 51 52 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset) 53 { 54 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 55 u8 bank = chip->registers - 1 - offset / 8; 56 u8 pin = offset % 8; 57 int ret; 58 59 mutex_lock(&chip->lock); 60 ret = (chip->buffer[bank] >> pin) & 0x1; 61 mutex_unlock(&chip->lock); 62 63 return ret; 64 } 65 66 static void gen_74x164_set_value(struct gpio_chip *gc, 67 unsigned offset, int val) 68 { 69 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 70 u8 bank = chip->registers - 1 - offset / 8; 71 u8 pin = offset % 8; 72 73 mutex_lock(&chip->lock); 74 if (val) 75 chip->buffer[bank] |= (1 << pin); 76 else 77 chip->buffer[bank] &= ~(1 << pin); 78 79 __gen_74x164_write_config(chip); 80 mutex_unlock(&chip->lock); 81 } 82 83 static int gen_74x164_direction_output(struct gpio_chip *gc, 84 unsigned offset, int val) 85 { 86 gen_74x164_set_value(gc, offset, val); 87 return 0; 88 } 89 90 static int gen_74x164_probe(struct spi_device *spi) 91 { 92 struct gen_74x164_chip *chip; 93 u32 nregs; 94 int ret; 95 96 /* 97 * bits_per_word cannot be configured in platform data 98 */ 99 spi->bits_per_word = 8; 100 101 ret = spi_setup(spi); 102 if (ret < 0) 103 return ret; 104 105 if (of_property_read_u32(spi->dev.of_node, "registers-number", 106 &nregs)) { 107 dev_err(&spi->dev, 108 "Missing registers-number property in the DT.\n"); 109 return -EINVAL; 110 } 111 112 chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL); 113 if (!chip) 114 return -ENOMEM; 115 116 spi_set_drvdata(spi, chip); 117 118 chip->gpio_chip.label = spi->modalias; 119 chip->gpio_chip.direction_output = gen_74x164_direction_output; 120 chip->gpio_chip.get = gen_74x164_get_value; 121 chip->gpio_chip.set = gen_74x164_set_value; 122 chip->gpio_chip.base = -1; 123 124 chip->registers = nregs; 125 chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers; 126 127 chip->gpio_chip.can_sleep = true; 128 chip->gpio_chip.parent = &spi->dev; 129 chip->gpio_chip.owner = THIS_MODULE; 130 131 mutex_init(&chip->lock); 132 133 ret = __gen_74x164_write_config(chip); 134 if (ret) { 135 dev_err(&spi->dev, "Failed writing: %d\n", ret); 136 goto exit_destroy; 137 } 138 139 ret = gpiochip_add(&chip->gpio_chip); 140 if (!ret) 141 return 0; 142 143 exit_destroy: 144 mutex_destroy(&chip->lock); 145 146 return ret; 147 } 148 149 static int gen_74x164_remove(struct spi_device *spi) 150 { 151 struct gen_74x164_chip *chip = spi_get_drvdata(spi); 152 153 gpiochip_remove(&chip->gpio_chip); 154 mutex_destroy(&chip->lock); 155 156 return 0; 157 } 158 159 static const struct of_device_id gen_74x164_dt_ids[] = { 160 { .compatible = "fairchild,74hc595" }, 161 {}, 162 }; 163 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids); 164 165 static struct spi_driver gen_74x164_driver = { 166 .driver = { 167 .name = "74x164", 168 .of_match_table = gen_74x164_dt_ids, 169 }, 170 .probe = gen_74x164_probe, 171 .remove = gen_74x164_remove, 172 }; 173 module_spi_driver(gen_74x164_driver); 174 175 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>"); 176 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>"); 177 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register"); 178 MODULE_LICENSE("GPL v2"); 179