gpio: Add driver for SPI serializers

Add generic parallel-in/serial-out shift register GPIO driver.

This includes SPI compatible devices like SN74165 serial-out shift
registers and the SN65HVS88x series of industrial serializers that can
be read over the SPI bus and used for GPI (General Purpose Input).

Signed-off-by: Andrew F. Davis <afd@ti.com>
Tested-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index f52b25964bc64747b0fe054164ff452a5e89d368..d003abeb175631bb1eee6dbc8d2616d648397eb3 100644 (file)
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1048,6 +1048,12 @@ config GPIO_MC33880
          SPI driver for Freescale MC33880 high-side/low-side switch.
          This provides GPIO interface supporting inputs and outputs.
 
+config GPIO_PISOSR
+       tristate "Generic parallel-in/serial-out shift register"
+       help
+         GPIO driver for SPI compatible parallel-in/serial-out shift
+         registers. These are input only devices.
+
 endmenu
 
 menu "SPI or I2C GPIO expanders"

diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 30ff7de0f6d5178f3b9b2d27f6319ecfecd5cc3d..85008de8b66dd3ecf0fad0f6b32ae9b8c9efaec8 100644 (file)
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_GPIO_OMAP)               += gpio-omap.o
 obj-$(CONFIG_GPIO_PCA953X)     += gpio-pca953x.o
 obj-$(CONFIG_GPIO_PCF857X)     += gpio-pcf857x.o
 obj-$(CONFIG_GPIO_PCH)         += gpio-pch.o
+obj-$(CONFIG_GPIO_PISOSR)      += gpio-pisosr.o
 obj-$(CONFIG_GPIO_PL061)       += gpio-pl061.o
 obj-$(CONFIG_GPIO_PXA)         += gpio-pxa.o
 obj-$(CONFIG_GPIO_RC5T583)     += gpio-rc5t583.o

diff --git a/drivers/gpio/gpio-pisosr.c b/drivers/gpio/gpio-pisosr.c
new file mode 100644 (file)
index 0000000..58ea08d
--- /dev/null
+++ b/drivers/gpio/gpio-pisosr.c
@@ -0,0 +1,188 @@
+/*
+ * 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(gpio->load_gpio, 1);
+               udelay(1); /* registers load time (~10ns) */
+               gpiod_set_value(gpio->load_gpio, 0);
+               udelay(1); /* registers recovery time (~5ns) */
+       }
+
+       ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
+       if (ret)
+               return ret;
+
+       mutex_unlock(&gpio->lock);
+
+       return 0;
+}
+
+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(dev, "load", GPIOD_OUT_LOW);
+       if (IS_ERR(gpio->load_gpio)) {
+               ret = PTR_ERR(gpio->load_gpio);
+               if (ret != -ENOENT && ret != -ENOSYS) {
+                       if (ret != -EPROBE_DEFER)
+                               dev_err(dev, "Unable to allocate load GPIO\n");
+                       return ret;
+               }
+               gpio->load_gpio = NULL;
+       }
+
+       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");