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 void gen_74x164_set_multiple(struct gpio_chip *gc, unsigned long *mask, 79 unsigned long *bits) 80 { 81 struct gen_74x164_chip *chip = gpiochip_get_data(gc); 82 unsigned int i, idx, shift; 83 u8 bank, bankmask; 84 85 mutex_lock(&chip->lock); 86 for (i = 0, bank = chip->registers - 1; i < chip->registers; 87 i++, bank--) { 88 idx = i / sizeof(*mask); 89 shift = i % sizeof(*mask) * BITS_PER_BYTE; 90 bankmask = mask[idx] >> shift; 91 if (!bankmask) 92 continue; 93 94 chip->buffer[bank] &= ~bankmask; 95 chip->buffer[bank] |= bankmask & (bits[idx] >> shift); 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 u32 nregs; 112 int ret; 113 114 /* 115 * bits_per_word cannot be configured in platform data 116 */ 117 spi->bits_per_word = 8; 118 119 ret = spi_setup(spi); 120 if (ret < 0) 121 return ret; 122 123 if (of_property_read_u32(spi->dev.of_node, "registers-number", 124 &nregs)) { 125 dev_err(&spi->dev, 126 "Missing registers-number property in the DT.\n"); 127 return -EINVAL; 128 } 129 130 chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL); 131 if (!chip) 132 return -ENOMEM; 133 134 spi_set_drvdata(spi, chip); 135 136 chip->gpio_chip.label = spi->modalias; 137 chip->gpio_chip.direction_output = gen_74x164_direction_output; 138 chip->gpio_chip.get = gen_74x164_get_value; 139 chip->gpio_chip.set = gen_74x164_set_value; 140 chip->gpio_chip.set_multiple = gen_74x164_set_multiple; 141 chip->gpio_chip.base = -1; 142 143 chip->registers = nregs; 144 chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers; 145 146 chip->gpio_chip.can_sleep = true; 147 chip->gpio_chip.parent = &spi->dev; 148 chip->gpio_chip.owner = THIS_MODULE; 149 150 mutex_init(&chip->lock); 151 152 ret = __gen_74x164_write_config(chip); 153 if (ret) { 154 dev_err(&spi->dev, "Failed writing: %d\n", ret); 155 goto exit_destroy; 156 } 157 158 ret = gpiochip_add_data(&chip->gpio_chip, chip); 159 if (!ret) 160 return 0; 161 162 exit_destroy: 163 mutex_destroy(&chip->lock); 164 165 return ret; 166 } 167 168 static int gen_74x164_remove(struct spi_device *spi) 169 { 170 struct gen_74x164_chip *chip = spi_get_drvdata(spi); 171 172 gpiochip_remove(&chip->gpio_chip); 173 mutex_destroy(&chip->lock); 174 175 return 0; 176 } 177 178 static const struct of_device_id gen_74x164_dt_ids[] = { 179 { .compatible = "fairchild,74hc595" }, 180 { .compatible = "nxp,74lvc594" }, 181 {}, 182 }; 183 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids); 184 185 static struct spi_driver gen_74x164_driver = { 186 .driver = { 187 .name = "74x164", 188 .of_match_table = gen_74x164_dt_ids, 189 }, 190 .probe = gen_74x164_probe, 191 .remove = gen_74x164_remove, 192 }; 193 module_spi_driver(gen_74x164_driver); 194 195 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>"); 196 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>"); 197 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register"); 198 MODULE_LICENSE("GPL v2"); 199