1 /* 2 * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/ 3 * Andrew F. Davis <afd@ti.com> 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 * 9 * This program is distributed "as is" WITHOUT ANY WARRANTY of any 10 * kind, whether expressed or implied; without even the implied warranty 11 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License version 2 for more details. 13 */ 14 15 #include <linux/bitmap.h> 16 #include <linux/bitops.h> 17 #include <linux/delay.h> 18 #include <linux/gpio/consumer.h> 19 #include <linux/gpio/driver.h> 20 #include <linux/module.h> 21 #include <linux/mutex.h> 22 #include <linux/spi/spi.h> 23 24 #define DEFAULT_NGPIO 8 25 26 /** 27 * struct pisosr_gpio - GPIO driver data 28 * @chip: GPIO controller chip 29 * @spi: SPI device pointer 30 * @buffer: Buffer for device reads 31 * @buffer_size: Size of buffer 32 * @load_gpio: GPIO pin used to load input into device 33 * @lock: Protects read sequences 34 */ 35 struct pisosr_gpio { 36 struct gpio_chip chip; 37 struct spi_device *spi; 38 u8 *buffer; 39 size_t buffer_size; 40 struct gpio_desc *load_gpio; 41 struct mutex lock; 42 }; 43 44 static int pisosr_gpio_refresh(struct pisosr_gpio *gpio) 45 { 46 int ret; 47 48 mutex_lock(&gpio->lock); 49 50 if (gpio->load_gpio) { 51 gpiod_set_value_cansleep(gpio->load_gpio, 1); 52 udelay(1); /* registers load time (~10ns) */ 53 gpiod_set_value_cansleep(gpio->load_gpio, 0); 54 udelay(1); /* registers recovery time (~5ns) */ 55 } 56 57 ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size); 58 59 mutex_unlock(&gpio->lock); 60 61 return ret; 62 } 63 64 static int pisosr_gpio_get_direction(struct gpio_chip *chip, 65 unsigned offset) 66 { 67 /* This device always input */ 68 return 1; 69 } 70 71 static int pisosr_gpio_direction_input(struct gpio_chip *chip, 72 unsigned offset) 73 { 74 /* This device always input */ 75 return 0; 76 } 77 78 static int pisosr_gpio_direction_output(struct gpio_chip *chip, 79 unsigned offset, int value) 80 { 81 /* This device is input only */ 82 return -EINVAL; 83 } 84 85 static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset) 86 { 87 struct pisosr_gpio *gpio = gpiochip_get_data(chip); 88 89 /* Refresh may not always be needed */ 90 pisosr_gpio_refresh(gpio); 91 92 return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1; 93 } 94 95 static int pisosr_gpio_get_multiple(struct gpio_chip *chip, 96 unsigned long *mask, unsigned long *bits) 97 { 98 struct pisosr_gpio *gpio = gpiochip_get_data(chip); 99 unsigned int nbytes = DIV_ROUND_UP(chip->ngpio, 8); 100 unsigned int i, j; 101 102 pisosr_gpio_refresh(gpio); 103 104 bitmap_zero(bits, chip->ngpio); 105 for (i = 0; i < nbytes; i++) { 106 j = i / sizeof(unsigned long); 107 bits[j] |= ((unsigned long) gpio->buffer[i]) 108 << (8 * (i % sizeof(unsigned long))); 109 } 110 111 return 0; 112 } 113 114 static const struct gpio_chip template_chip = { 115 .label = "pisosr-gpio", 116 .owner = THIS_MODULE, 117 .get_direction = pisosr_gpio_get_direction, 118 .direction_input = pisosr_gpio_direction_input, 119 .direction_output = pisosr_gpio_direction_output, 120 .get = pisosr_gpio_get, 121 .get_multiple = pisosr_gpio_get_multiple, 122 .base = -1, 123 .ngpio = DEFAULT_NGPIO, 124 .can_sleep = true, 125 }; 126 127 static int pisosr_gpio_probe(struct spi_device *spi) 128 { 129 struct device *dev = &spi->dev; 130 struct pisosr_gpio *gpio; 131 int ret; 132 133 gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL); 134 if (!gpio) 135 return -ENOMEM; 136 137 spi_set_drvdata(spi, gpio); 138 139 gpio->chip = template_chip; 140 gpio->chip.parent = dev; 141 of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio); 142 143 gpio->spi = spi; 144 145 gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8); 146 gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL); 147 if (!gpio->buffer) 148 return -ENOMEM; 149 150 gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW); 151 if (IS_ERR(gpio->load_gpio)) { 152 ret = PTR_ERR(gpio->load_gpio); 153 if (ret != -EPROBE_DEFER) 154 dev_err(dev, "Unable to allocate load GPIO\n"); 155 return ret; 156 } 157 158 mutex_init(&gpio->lock); 159 160 ret = gpiochip_add_data(&gpio->chip, gpio); 161 if (ret < 0) { 162 dev_err(dev, "Unable to register gpiochip\n"); 163 return ret; 164 } 165 166 return 0; 167 } 168 169 static int pisosr_gpio_remove(struct spi_device *spi) 170 { 171 struct pisosr_gpio *gpio = spi_get_drvdata(spi); 172 173 gpiochip_remove(&gpio->chip); 174 175 mutex_destroy(&gpio->lock); 176 177 return 0; 178 } 179 180 static const struct spi_device_id pisosr_gpio_id_table[] = { 181 { "pisosr-gpio", }, 182 { /* sentinel */ } 183 }; 184 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table); 185 186 static const struct of_device_id pisosr_gpio_of_match_table[] = { 187 { .compatible = "pisosr-gpio", }, 188 { /* sentinel */ } 189 }; 190 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table); 191 192 static struct spi_driver pisosr_gpio_driver = { 193 .driver = { 194 .name = "pisosr-gpio", 195 .of_match_table = pisosr_gpio_of_match_table, 196 }, 197 .probe = pisosr_gpio_probe, 198 .remove = pisosr_gpio_remove, 199 .id_table = pisosr_gpio_id_table, 200 }; 201 module_spi_driver(pisosr_gpio_driver); 202 203 MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>"); 204 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver"); 205 MODULE_LICENSE("GPL v2"); 206