Re: [PATCH v2 2/2] gpio: Add driver for SPI serializers

From: Sean NyekjÃr
Date: Fri Jan 29 2016 - 01:31:46 EST



On 2016-01-25 17:37, Andrew F. Davis wrote:
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@xxxxxx>
---
drivers/gpio/Kconfig | 6 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-pisosr.c | 188 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 195 insertions(+)
create mode 100644 drivers/gpio/gpio-pisosr.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c88dd24..bec3489 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1011,6 +1011,12 @@ 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 ece7d7c..8e4f09f 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -75,6 +75,7 @@ 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
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@xxxxxx>
+ *
+ * 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 */ }
Please add this :-)
{"ti,sn65hvs885", 0},
+};
+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@xxxxxx>");
+MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
+MODULE_LICENSE("GPL v2");
Hi Andrew

I have created an driver for the sn65hvs885 at the same time as you, and the output is nearly identical :-)
We are both missing the support for cacading devices, but i guess that can come later on.

/Sean