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/spi/74x164.h> 16 #include <linux/gpio.h> 17 #include <linux/of_gpio.h> 18 #include <linux/slab.h> 19 #include <linux/module.h> 20 21 #define GEN_74X164_NUMBER_GPIOS 8 22 23 struct gen_74x164_chip { 24 struct spi_device *spi; 25 u8 *buffer; 26 struct gpio_chip gpio_chip; 27 struct mutex lock; 28 u32 registers; 29 }; 30 31 static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc) 32 { 33 return container_of(gc, struct gen_74x164_chip, gpio_chip); 34 } 35 36 static int __gen_74x164_write_config(struct gen_74x164_chip *chip) 37 { 38 struct spi_message message; 39 struct spi_transfer *msg_buf; 40 int i, ret = 0; 41 42 msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer), 43 GFP_KERNEL); 44 if (!msg_buf) 45 return -ENOMEM; 46 47 spi_message_init(&message); 48 49 /* 50 * Since the registers are chained, every byte sent will make 51 * the previous byte shift to the next register in the 52 * chain. Thus, the first byte send will end up in the last 53 * register at the end of the transfer. So, to have a logical 54 * numbering, send the bytes in reverse order so that the last 55 * byte of the buffer will end up in the last register. 56 */ 57 for (i = chip->registers - 1; i >= 0; i--) { 58 msg_buf[i].tx_buf = chip->buffer +i; 59 msg_buf[i].len = sizeof(u8); 60 spi_message_add_tail(msg_buf + i, &message); 61 } 62 63 ret = spi_sync(chip->spi, &message); 64 65 kfree(msg_buf); 66 67 return ret; 68 } 69 70 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset) 71 { 72 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 73 u8 bank = offset / 8; 74 u8 pin = offset % 8; 75 int ret; 76 77 mutex_lock(&chip->lock); 78 ret = (chip->buffer[bank] >> pin) & 0x1; 79 mutex_unlock(&chip->lock); 80 81 return ret; 82 } 83 84 static void gen_74x164_set_value(struct gpio_chip *gc, 85 unsigned offset, int val) 86 { 87 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 88 u8 bank = offset / 8; 89 u8 pin = offset % 8; 90 91 mutex_lock(&chip->lock); 92 if (val) 93 chip->buffer[bank] |= (1 << pin); 94 else 95 chip->buffer[bank] &= ~(1 << pin); 96 97 __gen_74x164_write_config(chip); 98 mutex_unlock(&chip->lock); 99 } 100 101 static int gen_74x164_direction_output(struct gpio_chip *gc, 102 unsigned offset, int val) 103 { 104 gen_74x164_set_value(gc, offset, val); 105 return 0; 106 } 107 108 static int gen_74x164_probe(struct spi_device *spi) 109 { 110 struct gen_74x164_chip *chip; 111 struct gen_74x164_chip_platform_data *pdata; 112 int ret; 113 114 if (!spi->dev.of_node) { 115 dev_err(&spi->dev, "No device tree data available.\n"); 116 return -EINVAL; 117 } 118 119 /* 120 * bits_per_word cannot be configured in platform data 121 */ 122 spi->bits_per_word = 8; 123 124 ret = spi_setup(spi); 125 if (ret < 0) 126 return ret; 127 128 chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL); 129 if (!chip) 130 return -ENOMEM; 131 132 pdata = spi->dev.platform_data; 133 if (pdata && pdata->base) 134 chip->gpio_chip.base = pdata->base; 135 else 136 chip->gpio_chip.base = -1; 137 138 mutex_init(&chip->lock); 139 140 spi_set_drvdata(spi, chip); 141 142 chip->spi = spi; 143 144 chip->gpio_chip.label = spi->modalias; 145 chip->gpio_chip.direction_output = gen_74x164_direction_output; 146 chip->gpio_chip.get = gen_74x164_get_value; 147 chip->gpio_chip.set = gen_74x164_set_value; 148 149 if (of_property_read_u32(spi->dev.of_node, "registers-number", &chip->registers)) { 150 dev_err(&spi->dev, "Missing registers-number property in the DT.\n"); 151 ret = -EINVAL; 152 goto exit_destroy; 153 } 154 155 chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers; 156 chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL); 157 if (!chip->buffer) { 158 ret = -ENOMEM; 159 goto exit_destroy; 160 } 161 162 chip->gpio_chip.can_sleep = 1; 163 chip->gpio_chip.dev = &spi->dev; 164 chip->gpio_chip.owner = THIS_MODULE; 165 166 ret = __gen_74x164_write_config(chip); 167 if (ret) { 168 dev_err(&spi->dev, "Failed writing: %d\n", ret); 169 goto exit_destroy; 170 } 171 172 ret = gpiochip_add(&chip->gpio_chip); 173 if (ret) 174 goto exit_destroy; 175 176 return ret; 177 178 exit_destroy: 179 spi_set_drvdata(spi, NULL); 180 mutex_destroy(&chip->lock); 181 return ret; 182 } 183 184 static int gen_74x164_remove(struct spi_device *spi) 185 { 186 struct gen_74x164_chip *chip; 187 int ret; 188 189 chip = spi_get_drvdata(spi); 190 if (chip == NULL) 191 return -ENODEV; 192 193 spi_set_drvdata(spi, NULL); 194 195 ret = gpiochip_remove(&chip->gpio_chip); 196 if (!ret) 197 mutex_destroy(&chip->lock); 198 else 199 dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n", 200 ret); 201 202 return ret; 203 } 204 205 static const struct of_device_id gen_74x164_dt_ids[] = { 206 { .compatible = "fairchild,74hc595" }, 207 {}, 208 }; 209 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids); 210 211 static struct spi_driver gen_74x164_driver = { 212 .driver = { 213 .name = "74x164", 214 .owner = THIS_MODULE, 215 .of_match_table = of_match_ptr(gen_74x164_dt_ids), 216 }, 217 .probe = gen_74x164_probe, 218 .remove = gen_74x164_remove, 219 }; 220 module_spi_driver(gen_74x164_driver); 221 222 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>"); 223 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>"); 224 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register"); 225 MODULE_LICENSE("GPL v2"); 226