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[PATCH v2 0/2] gpio: Add driver for SPI serializers

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  [PATCH v2 0/2] gpio: Add driver for SPI serializers "Andrew F. Davis" <afd@ti.com> - 2016-01-25 17:40 +0100
    [PATCH v2 1/2] dt-bindings: GPIO: Add generic serializer binding "Andrew F. Davis" <afd@ti.com> - 2016-01-25 17:40 +0100
      Re: [PATCH v2 1/2] dt-bindings: GPIO: Add generic serializer binding Rob Herring <robh@kernel.org> - 2016-01-25 20:40 +0100
    [PATCH v2 2/2] gpio: Add driver for SPI serializers "Andrew F. Davis" <afd@ti.com> - 2016-01-25 17:50 +0100

#1316968 — [PATCH v2 0/2] gpio: Add driver for SPI serializers

This series adds a GPI(General Purpose Input) driver for generic
parallel-in/serial-out shift registers, such as the SN65HVS882
that this driver was tested on. This should also work for the rest
of the SN65HVS88x series as well as other 74x165 style devices.

Changes from v1[0]:
 - Use new gpiochip_add_data
 - Rebased on v4.5-rc1
 - Small fixes

[0] http://www.spinics.net/lists/linux-gpio/msg10563.html

Andrew F. Davis (2):
  dt-bindings: GPIO: Add generic serializer binding
  gpio: Add driver for SPI serializers

 .../devicetree/bindings/gpio/gpio-pisosr.txt       |  34 ++++
 drivers/gpio/Kconfig                               |   6 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-pisosr.c                         | 188 +++++++++++++++++++++
 4 files changed, 229 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-pisosr.txt
 create mode 100644 drivers/gpio/gpio-pisosr.c

-- 
2.7.0

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#1316974 — [PATCH v2 1/2] dt-bindings: GPIO: Add generic serializer binding

Add binding for generic parallel-in/serial-out shift register devices
used as GPIO.

Signed-off-by: Andrew F. Davis <afd@ti.com>
---
 .../devicetree/bindings/gpio/gpio-pisosr.txt       | 34 ++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-pisosr.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt b/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt
new file mode 100644
index 0000000..e69e8ec
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt
@@ -0,0 +1,34 @@
+Generic Parallel-in/Serial-out Shift Register GPIO Driver
+
+This binding describes generic parallel-in/serial-out shift register
+devices that can be used for GPI (General Purpose Input). This includes
+SN74165 serial-out shift registers and the SN65HVS88x series of
+industrial serializers.
+
+Required properties:
+ - compatible		: Should be "pisosr-gpio".
+ - gpio-controller	: Marks the device node as a GPIO controller.
+ - #gpio-cells		: Should be two. For consumer use see gpio.txt.
+
+Optional properties:
+ - ngpios		: Number of GPIO lines, default is 8.
+ - load-gpios		: GPIO pin specifier attached to load enable, this
+			  pin is pulsed before reading from the device to
+			  load input pin values into the the device.
+
+For other required and optional properties of SPI slave
+nodes please refer to ../spi/spi-bus.txt.
+
+Example:
+
+	sn65hvs882@0 {
+		compatible = "pisosr-gpio";
+		gpio-controller;
+		#gpio-cells = <2>;
+
+		load-gpios = <&gpio2 23 GPIO_ACTIVE_LOW>;
+
+		reg = <0>;
+		spi-max-frequency = <1000000>;
+		spi-cpol;
+	};
-- 
2.7.0

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#1317236 — Re: [PATCH v2 1/2] dt-bindings: GPIO: Add generic serializer binding

On Mon, Jan 25, 2016 at 10:37:30AM -0600, Andrew F. Davis wrote:
> Add binding for generic parallel-in/serial-out shift register devices
> used as GPIO.
> 
> Signed-off-by: Andrew F. Davis <afd@ti.com>
> ---
>  .../devicetree/bindings/gpio/gpio-pisosr.txt       | 34 ++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-pisosr.txt

One nit, otherwise:

Acked-by: Rob Herring <robh@kernel.org>

> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt b/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt
> new file mode 100644
> index 0000000..e69e8ec
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/gpio/gpio-pisosr.txt
> @@ -0,0 +1,34 @@
> +Generic Parallel-in/Serial-out Shift Register GPIO Driver
> +
> +This binding describes generic parallel-in/serial-out shift register
> +devices that can be used for GPI (General Purpose Input). This includes
> +SN74165 serial-out shift registers and the SN65HVS88x series of
> +industrial serializers.
> +
> +Required properties:
> + - compatible		: Should be "pisosr-gpio".
> + - gpio-controller	: Marks the device node as a GPIO controller.
> + - #gpio-cells		: Should be two. For consumer use see gpio.txt.
> +
> +Optional properties:
> + - ngpios		: Number of GPIO lines, default is 8.
> + - load-gpios		: GPIO pin specifier attached to load enable, this
> +			  pin is pulsed before reading from the device to
> +			  load input pin values into the the device.
> +
> +For other required and optional properties of SPI slave
> +nodes please refer to ../spi/spi-bus.txt.
> +
> +Example:
> +
> +	sn65hvs882@0 {

should be gpio@0

> +		compatible = "pisosr-gpio";
> +		gpio-controller;
> +		#gpio-cells = <2>;
> +
> +		load-gpios = <&gpio2 23 GPIO_ACTIVE_LOW>;
> +
> +		reg = <0>;
> +		spi-max-frequency = <1000000>;
> +		spi-cpol;
> +	};
> -- 
> 2.7.0
> 

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#1316994 — [PATCH v2 2/2] 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>
---
 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@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");
-- 
2.7.0

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