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"); 194