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"); 174