diff options
Diffstat (limited to 'drivers/gpio/gpio-pisosr.c')
| -rw-r--r-- | drivers/gpio/gpio-pisosr.c | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/drivers/gpio/gpio-pisosr.c b/drivers/gpio/gpio-pisosr.c new file mode 100644 index 0000000..cb14b8d --- /dev/null +++ b/drivers/gpio/gpio-pisosr.c @@ -0,0 +1,183 @@ +/* + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/ + * Andrew F. Davis <afd@ti.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed "as is" WITHOUT ANY WARRANTY of any + * kind, whether expressed or implied; without even the implied warranty + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License version 2 for more details. + */ + +#include <linux/delay.h> +#include <linux/gpio/consumer.h> +#include <linux/gpio/driver.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/spi/spi.h> + +#define DEFAULT_NGPIO 8 + +/** + * struct pisosr_gpio - GPIO driver data + * @chip: GPIO controller chip + * @spi: SPI device pointer + * @buffer: Buffer for device reads + * @buffer_size: Size of buffer + * @load_gpio: GPIO pin used to load input into device + * @lock: Protects read sequences + */ +struct pisosr_gpio { + struct gpio_chip chip; + struct spi_device *spi; + u8 *buffer; + size_t buffer_size; + struct gpio_desc *load_gpio; + struct mutex lock; +}; + +static int pisosr_gpio_refresh(struct pisosr_gpio *gpio) +{ + int ret; + + mutex_lock(&gpio->lock); + + if (gpio->load_gpio) { + gpiod_set_value_cansleep(gpio->load_gpio, 1); + udelay(1); /* registers load time (~10ns) */ + gpiod_set_value_cansleep(gpio->load_gpio, 0); + udelay(1); /* registers recovery time (~5ns) */ + } + + ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size); + + mutex_unlock(&gpio->lock); + + return ret; +} + +static int pisosr_gpio_get_direction(struct gpio_chip *chip, + unsigned offset) +{ + /* This device always input */ + return 1; +} + +static int pisosr_gpio_direction_input(struct gpio_chip *chip, + unsigned offset) +{ + /* This device always input */ + return 0; +} + +static int pisosr_gpio_direction_output(struct gpio_chip *chip, + unsigned offset, int value) +{ + /* This device is input only */ + return -EINVAL; +} + +static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset) +{ + struct pisosr_gpio *gpio = gpiochip_get_data(chip); + + /* Refresh may not always be needed */ + pisosr_gpio_refresh(gpio); + + return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1; +} + +static struct gpio_chip template_chip = { + .label = "pisosr-gpio", + .owner = THIS_MODULE, + .get_direction = pisosr_gpio_get_direction, + .direction_input = pisosr_gpio_direction_input, + .direction_output = pisosr_gpio_direction_output, + .get = pisosr_gpio_get, + .base = -1, + .ngpio = DEFAULT_NGPIO, + .can_sleep = true, +}; + +static int pisosr_gpio_probe(struct spi_device *spi) +{ + struct device *dev = &spi->dev; + struct pisosr_gpio *gpio; + int ret; + + gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL); + if (!gpio) + return -ENOMEM; + + spi_set_drvdata(spi, gpio); + + gpio->chip = template_chip; + gpio->chip.parent = dev; + of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio); + + gpio->spi = spi; + + gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8); + gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL); + if (!gpio->buffer) + return -ENOMEM; + + gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW); + if (IS_ERR(gpio->load_gpio)) { + ret = PTR_ERR(gpio->load_gpio); + if (ret != -EPROBE_DEFER) + dev_err(dev, "Unable to allocate load GPIO\n"); + return ret; + } + + mutex_init(&gpio->lock); + + ret = gpiochip_add_data(&gpio->chip, gpio); + if (ret < 0) { + dev_err(dev, "Unable to register gpiochip\n"); + return ret; + } + + return 0; +} + +static int pisosr_gpio_remove(struct spi_device *spi) +{ + struct pisosr_gpio *gpio = spi_get_drvdata(spi); + + gpiochip_remove(&gpio->chip); + + mutex_destroy(&gpio->lock); + + return 0; +} + +static const struct spi_device_id pisosr_gpio_id_table[] = { + { "pisosr-gpio", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table); + +static const struct of_device_id pisosr_gpio_of_match_table[] = { + { .compatible = "pisosr-gpio", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table); + +static struct spi_driver pisosr_gpio_driver = { + .driver = { + .name = "pisosr-gpio", + .of_match_table = pisosr_gpio_of_match_table, + }, + .probe = pisosr_gpio_probe, + .remove = pisosr_gpio_remove, + .id_table = pisosr_gpio_id_table, +}; +module_spi_driver(pisosr_gpio_driver); + +MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>"); +MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver"); +MODULE_LICENSE("GPL v2"); |
