drivers/gpio/gpio-pisosr.c

   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 const 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");