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/delay.h> 16 #include <linux/gpio/consumer.h> 17 #include <linux/gpio/driver.h> 18 #include <linux/module.h> 19 #include <linux/mutex.h> 20 #include <linux/spi/spi.h> 21 22 #define DEFAULT_NGPIO 8 23 24 /** 25 * struct pisosr_gpio - GPIO driver data 26 * @chip: GPIO controller chip 27 * @spi: SPI device pointer 28 * @buffer: Buffer for device reads 29 * @buffer_size: Size of buffer 30 * @load_gpio: GPIO pin used to load input into device 31 * @lock: Protects read sequences 32 */ 33 struct pisosr_gpio { 34 struct gpio_chip chip; 35 struct spi_device *spi; 36 u8 *buffer; 37 size_t buffer_size; 38 struct gpio_desc *load_gpio; 39 struct mutex lock; 40 }; 41 42 static int pisosr_gpio_refresh(struct pisosr_gpio *gpio) 43 { 44 int ret; 45 46 mutex_lock(&gpio->lock); 47 48 if (gpio->load_gpio) { 49 gpiod_set_value_cansleep(gpio->load_gpio, 1); 50 udelay(1); /* registers load time (~10ns) */ 51 gpiod_set_value_cansleep(gpio->load_gpio, 0); 52 udelay(1); /* registers recovery time (~5ns) */ 53 } 54 55 ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size); 56 57 mutex_unlock(&gpio->lock); 58 59 return ret; 60 } 61 62 static int pisosr_gpio_get_direction(struct gpio_chip *chip, 63 unsigned offset) 64 { 65 /* This device always input */ 66 return 1; 67 } 68 69 static int pisosr_gpio_direction_input(struct gpio_chip *chip, 70 unsigned offset) 71 { 72 /* This device always input */ 73 return 0; 74 } 75 76 static int pisosr_gpio_direction_output(struct gpio_chip *chip, 77 unsigned offset, int value) 78 { 79 /* This device is input only */ 80 return -EINVAL; 81 } 82 83 static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset) 84 { 85 struct pisosr_gpio *gpio = gpiochip_get_data(chip); 86 87 /* Refresh may not always be needed */ 88 pisosr_gpio_refresh(gpio); 89 90 return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1; 91 } 92 93 static struct gpio_chip template_chip = { 94 .label = "pisosr-gpio", 95 .owner = THIS_MODULE, 96 .get_direction = pisosr_gpio_get_direction, 97 .direction_input = pisosr_gpio_direction_input, 98 .direction_output = pisosr_gpio_direction_output, 99 .get = pisosr_gpio_get, 100 .base = -1, 101 .ngpio = DEFAULT_NGPIO, 102 .can_sleep = true, 103 }; 104 105 static int pisosr_gpio_probe(struct spi_device *spi) 106 { 107 struct device *dev = &spi->dev; 108 struct pisosr_gpio *gpio; 109 int ret; 110 111 gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL); 112 if (!gpio) 113 return -ENOMEM; 114 115 spi_set_drvdata(spi, gpio); 116 117 gpio->chip = template_chip; 118 gpio->chip.parent = dev; 119 of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio); 120 121 gpio->spi = spi; 122 123 gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8); 124 gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL); 125 if (!gpio->buffer) 126 return -ENOMEM; 127 128 gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW); 129 if (IS_ERR(gpio->load_gpio)) { 130 ret = PTR_ERR(gpio->load_gpio); 131 if (ret != -EPROBE_DEFER) 132 dev_err(dev, "Unable to allocate load GPIO\n"); 133 return ret; 134 } 135 136 mutex_init(&gpio->lock); 137 138 ret = gpiochip_add_data(&gpio->chip, gpio); 139 if (ret < 0) { 140 dev_err(dev, "Unable to register gpiochip\n"); 141 return ret; 142 } 143 144 return 0; 145 } 146 147 static int pisosr_gpio_remove(struct spi_device *spi) 148 { 149 struct pisosr_gpio *gpio = spi_get_drvdata(spi); 150 151 gpiochip_remove(&gpio->chip); 152 153 mutex_destroy(&gpio->lock); 154 155 return 0; 156 } 157 158 static const struct spi_device_id pisosr_gpio_id_table[] = { 159 { "pisosr-gpio", }, 160 { /* sentinel */ } 161 }; 162 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table); 163 164 static const struct of_device_id pisosr_gpio_of_match_table[] = { 165 { .compatible = "pisosr-gpio", }, 166 { /* sentinel */ } 167 }; 168 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table); 169 170 static struct spi_driver pisosr_gpio_driver = { 171 .driver = { 172 .name = "pisosr-gpio", 173 .of_match_table = pisosr_gpio_of_match_table, 174 }, 175 .probe = pisosr_gpio_probe, 176 .remove = pisosr_gpio_remove, 177 .id_table = pisosr_gpio_id_table, 178 }; 179 module_spi_driver(pisosr_gpio_driver); 180 181 MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>"); 182 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver"); 183 MODULE_LICENSE("GPL v2"); 184