drivers/gpio/gpio-pisosr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2015-2023 Texas Instruments Incorporated - https://www.ti.com/
   4  *      Andrew Davis <afd@ti.com>
   5  */
   6
   7 #include <linux/bitmap.h>
   8 #include <linux/bitops.h>
   9 #include <linux/delay.h>
  10 #include <linux/gpio/consumer.h>
  11 #include <linux/gpio/driver.h>
  12 #include <linux/module.h>
  13 #include <linux/mutex.h>
  14 #include <linux/spi/spi.h>
  15
  16 #define DEFAULT_NGPIO 8
  17
  18 /**
  19  * struct pisosr_gpio - GPIO driver data
  20  * @chip: GPIO controller chip
  21  * @spi: SPI device pointer
  22  * @buffer: Buffer for device reads
  23  * @buffer_size: Size of buffer
  24  * @load_gpio: GPIO pin used to load input into device
  25  * @lock: Protects read sequences
  26  */
  27 struct pisosr_gpio {
  28         struct gpio_chip chip;
  29         struct spi_device *spi;
  30         u8 *buffer;
  31         size_t buffer_size;
  32         struct gpio_desc *load_gpio;
  33         struct mutex lock;
  34 };
  35
  36 static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
  37 {
  38         int ret;
  39
  40         mutex_lock(&gpio->lock);
  41
  42         if (gpio->load_gpio) {
  43                 gpiod_set_value_cansleep(gpio->load_gpio, 1);
  44                 udelay(1); /* registers load time (~10ns) */
  45                 gpiod_set_value_cansleep(gpio->load_gpio, 0);
  46                 udelay(1); /* registers recovery time (~5ns) */
  47         }
  48
  49         ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
  50
  51         mutex_unlock(&gpio->lock);
  52
  53         return ret;
  54 }
  55
  56 static int pisosr_gpio_get_direction(struct gpio_chip *chip,
  57                                      unsigned offset)
  58 {
  59         /* This device always input */
  60         return GPIO_LINE_DIRECTION_IN;
  61 }
  62
  63 static int pisosr_gpio_direction_input(struct gpio_chip *chip,
  64                                        unsigned offset)
  65 {
  66         /* This device always input */
  67         return 0;
  68 }
  69
  70 static int pisosr_gpio_direction_output(struct gpio_chip *chip,
  71                                         unsigned offset, int value)
  72 {
  73         /* This device is input only */
  74         return -EINVAL;
  75 }
  76
  77 static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
  78 {
  79         struct pisosr_gpio *gpio = gpiochip_get_data(chip);
  80
  81         /* Refresh may not always be needed */
  82         pisosr_gpio_refresh(gpio);
  83
  84         return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
  85 }
  86
  87 static int pisosr_gpio_get_multiple(struct gpio_chip *chip,
  88                                     unsigned long *mask, unsigned long *bits)
  89 {
  90         struct pisosr_gpio *gpio = gpiochip_get_data(chip);
  91         unsigned long offset;
  92         unsigned long gpio_mask;
  93         unsigned long buffer_state;
  94
  95         pisosr_gpio_refresh(gpio);
  96
  97         bitmap_zero(bits, chip->ngpio);
  98         for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
  99                 buffer_state = gpio->buffer[offset / 8] & gpio_mask;
 100                 bitmap_set_value8(bits, buffer_state, offset);
 101         }
 102
 103         return 0;
 104 }
 105
 106 static const struct gpio_chip template_chip = {
 107         .label                  = "pisosr-gpio",
 108         .owner                  = THIS_MODULE,
 109         .get_direction          = pisosr_gpio_get_direction,
 110         .direction_input        = pisosr_gpio_direction_input,
 111         .direction_output       = pisosr_gpio_direction_output,
 112         .get                    = pisosr_gpio_get,
 113         .get_multiple           = pisosr_gpio_get_multiple,
 114         .base                   = -1,
 115         .ngpio                  = DEFAULT_NGPIO,
 116         .can_sleep              = true,
 117 };
 118
 119 static void pisosr_mutex_destroy(void *lock)
 120 {
 121         mutex_destroy(lock);
 122 }
 123
 124 static int pisosr_gpio_probe(struct spi_device *spi)
 125 {
 126         struct device *dev = &spi->dev;
 127         struct pisosr_gpio *gpio;
 128         int ret;
 129
 130         gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
 131         if (!gpio)
 132                 return -ENOMEM;
 133
 134         gpio->chip = template_chip;
 135         gpio->chip.parent = dev;
 136         of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
 137
 138         gpio->spi = spi;
 139
 140         gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
 141         gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
 142         if (!gpio->buffer)
 143                 return -ENOMEM;
 144
 145         gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
 146         if (IS_ERR(gpio->load_gpio))
 147                 return dev_err_probe(dev, PTR_ERR(gpio->load_gpio),
 148                                      "Unable to allocate load GPIO\n");
 149
 150         mutex_init(&gpio->lock);
 151         ret = devm_add_action_or_reset(dev, pisosr_mutex_destroy, &gpio->lock);
 152         if (ret)
 153                 return ret;
 154
 155         ret = devm_gpiochip_add_data(dev, &gpio->chip, gpio);
 156         if (ret < 0) {
 157                 dev_err(dev, "Unable to register gpiochip\n");
 158                 return ret;
 159         }
 160
 161         return 0;
 162 }
 163
 164 static const struct spi_device_id pisosr_gpio_id_table[] = {
 165         { "pisosr-gpio", },
 166         { /* sentinel */ }
 167 };
 168 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
 169
 170 static const struct of_device_id pisosr_gpio_of_match_table[] = {
 171         { .compatible = "pisosr-gpio", },
 172         { /* sentinel */ }
 173 };
 174 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
 175
 176 static struct spi_driver pisosr_gpio_driver = {
 177         .driver = {
 178                 .name = "pisosr-gpio",
 179                 .of_match_table = pisosr_gpio_of_match_table,
 180         },
 181         .probe = pisosr_gpio_probe,
 182         .id_table = pisosr_gpio_id_table,
 183 };
 184 module_spi_driver(pisosr_gpio_driver);
 185
 186 MODULE_AUTHOR("Andrew Davis <afd@ti.com>");
 187 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
 188 MODULE_LICENSE("GPL v2");