[PATCH 2/2] gpio: Port SX150x driver from Linux

[Andrey Smirnov <andrew.smirnov@gmail.com>]

Add a very abridged version of SX150x driver from Linux. New, "pinctrl"
version of the driver was used as a base. As it was already mentioned
this driver supports very limited amount of the original functionality,
and the following are the features that were dropped:
     - Interrupt support
     - Support for any chip other that SX150x (due to lack of HW to test
       with)
     - Any pinctlr-like functions: pull-up/pull-down, open-drain,
       etc. configuration

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/gpio/Kconfig       |   8 ++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-sx150x.c | 274 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 283 insertions(+)
 create mode 100644 drivers/gpio/gpio-sx150x.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index fe62778..434c568 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -124,6 +124,14 @@ config GPIO_DESIGNWARE
 	help
 	  Say Y or M here to build support for the Synopsys DesignWare APB
 	  GPIO block.
+
+config GPIO_SX150X
+	bool "Semtec SX150x I/O ports"
+	depends on I2C
+	help
+	  Say Y here to build support for the Semtec Sx150x I2C GPIO
+	  expander chip.
+
 endmenu
 
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 248100f..7442c44 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -19,3 +19,4 @@ obj-$(CONFIG_GPIO_STMPE)	+= gpio-stmpe.o
 obj-$(CONFIG_GPIO_TEGRA)	+= gpio-tegra.o
 obj-$(CONFIG_GPIO_DESIGNWARE)	+= gpio-dw.o
 obj-$(CONFIG_GPIO_VF610)	+= gpio-vf610.o
+obj-$(CONFIG_GPIO_SX150X)	+= gpio-sx150x.o
diff --git a/drivers/gpio/gpio-sx150x.c b/drivers/gpio/gpio-sx150x.c
new file mode 100644
index 0000000..7b8cfb5
--- /dev/null
+++ b/drivers/gpio/gpio-sx150x.c
@@ -0,0 +1,274 @@
+/*
+ *  Driver for SX150x I2C GPIO expanders
+ *
+ *  This code was ported from linux-4.9 kernel driver by
+ *  Andrey Smirnov <andrew.smirnov@gmail.com>.
+ *
+ *  Orginal code with it's copyright info can be found in
+ *  drivers/pinctrl/pinctrl-sx150x.c
+ *
+ *  Note: That although linux driver was converted from being a GPIO
+ *  subsystem to Pinctrl subsytem driver, due to Barebox's lack of
+ *  similar provisions this driver is still a GPIO driver.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ */
+
+#include <common.h>
+#include <init.h>
+#include <malloc.h>
+#include <driver.h>
+#include <xfuncs.h>
+#include <errno.h>
+#include <i2c/i2c.h>
+#include <regmap.h>
+
+#include <gpio.h>
+#include <of_device.h>
+
+enum {
+	SX150X_123 = 0,
+	SX150X_456,
+	SX150X_789,
+};
+
+enum {
+	SX150X_MAX_REGISTER = 0xad,
+};
+
+struct sx150x_device_data {
+	u8 model;
+	u8 reg_dir;
+	u8 reg_data;
+	u8 ngpios;
+};
+
+struct sx150x_gpio {
+	struct device *dev;
+	struct i2c_client *client;
+	struct gpio_chip gpio;
+	struct regmap *regmap;
+	const struct sx150x_device_data *data;
+};
+
+static const struct sx150x_device_data sx1503q_device_data = {
+	.model    = SX150X_123,
+	.reg_dir  = 0x02,
+	.reg_data = 0x00,
+	.ngpios	  = 16,
+};
+
+static struct sx150x_gpio *to_sx150x_gpio(struct gpio_chip *gpio)
+{
+	return container_of(gpio, struct sx150x_gpio, gpio);
+}
+
+static int sx150x_gpio_get_direction(struct gpio_chip *gpio,
+				      unsigned int offset)
+{
+	struct sx150x_gpio *sx150x = to_sx150x_gpio(gpio);
+	unsigned int value;
+	int ret;
+
+	ret = regmap_read(sx150x->regmap, sx150x->data->reg_dir, &value);
+	if (ret < 0)
+		return ret;
+
+	return !!(value & BIT(offset));
+}
+
+static int sx150x_gpio_get(struct gpio_chip *gpio, unsigned int offset)
+{
+	struct sx150x_gpio *sx150x = to_sx150x_gpio(gpio);
+	unsigned int value;
+	int ret;
+
+	ret = regmap_read(sx150x->regmap, sx150x->data->reg_data, &value);
+	if (ret < 0)
+		return ret;
+
+	return !!(value & BIT(offset));
+}
+
+static int __sx150x_gpio_set(struct sx150x_gpio *sx150x, unsigned int offset,
+			     int value)
+{
+	return regmap_write_bits(sx150x->regmap, sx150x->data->reg_data,
+				 BIT(offset), value ? BIT(offset) : 0);
+}
+
+
+static void sx150x_gpio_set(struct gpio_chip *gpio, unsigned int offset,
+			    int value)
+{
+	__sx150x_gpio_set(to_sx150x_gpio(gpio), offset, value);
+}
+
+static int sx150x_gpio_direction_input(struct gpio_chip *gpio,
+				       unsigned int offset)
+{
+	struct sx150x_gpio *sx150x = to_sx150x_gpio(gpio);
+
+	return regmap_write_bits(sx150x->regmap,
+				 sx150x->data->reg_dir,
+				 BIT(offset), BIT(offset));
+}
+
+static int sx150x_gpio_direction_output(struct gpio_chip *gpio,
+				       unsigned int offset, int value)
+{
+	struct sx150x_gpio *sx150x = to_sx150x_gpio(gpio);
+	int ret;
+
+	ret = __sx150x_gpio_set(sx150x, offset, value);
+	if (ret < 0)
+		return ret;
+
+	return regmap_write_bits(sx150x->regmap,
+				 sx150x->data->reg_dir,
+				 BIT(offset), 0);
+}
+
+static int sx150x_regmap_reg_width(struct sx150x_gpio *sx150x,
+				   unsigned int reg)
+{
+	return sx150x->data->ngpios;
+}
+
+/*
+ * In order to mask the differences between 16 and 8 bit expander
+ * devices we set up a sligthly ficticious regmap that pretends to be
+ * a set of 16-bit registers and transparently reconstructs those
+ * registers via multiple I2C/SMBus reads
+ *
+ * This way the rest of the driver code, interfacing with the chip via
+ * regmap API, can work assuming that each GPIO pin is represented by
+ * a group of bits at an offset proportioan to GPIO number within a
+ * given register.
+ *
+ */
+static int sx150x_regmap_reg_read(void *context, unsigned int reg,
+				  unsigned int *result)
+{
+	int ret, n;
+	struct sx150x_gpio *sx150x = context;
+	struct i2c_client *i2c = sx150x->client;
+	const int width = sx150x_regmap_reg_width(sx150x, reg);
+	unsigned int idx, val;
+
+	/*
+	 * There are four potential cases coverd by this function:
+	 *
+	 * 1) 8-pin chip, single configuration bit register
+	 *
+	 *	This is trivial the code below just needs to read:
+	 *		reg  [ 7 6 5 4 3 2 1 0 ]
+	 *
+	 * 2) 16-pin chip, single configuration bit register
+	 *
+	 *	The read will be done as follows:
+	 *		reg     [ f e d c b a 9 8 ]
+	 *		reg + 1 [ 7 6 5 4 3 2 1 0 ]
+	 *
+	 */
+
+	for (n = width, val = 0, idx = reg; n > 0; n -= 8, idx++) {
+		val <<= 8;
+
+		ret = i2c_smbus_read_byte_data(i2c, idx);
+		if (ret < 0)
+			return ret;
+
+		val |= ret;
+	}
+
+	*result = val;
+
+	return 0;
+}
+
+static int sx150x_regmap_reg_write(void *context, unsigned int reg,
+				   unsigned int val)
+{
+	int ret, n;
+	struct sx150x_gpio *sx150x = context;
+	struct i2c_client *i2c = sx150x->client;
+	const int width = sx150x_regmap_reg_width(sx150x, reg);
+
+	n = width - 8;
+	do {
+		const u8 byte = (val >> n) & 0xff;
+
+		ret = i2c_smbus_write_byte_data(i2c, reg, byte);
+		if (ret < 0)
+			return ret;
+
+		reg++;
+		n -= 8;
+	} while (n >= 0);
+
+	return 0;
+}
+
+static const struct regmap_config sx150x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+
+	.max_register = SX150X_MAX_REGISTER,
+};
+
+static const struct regmap_bus sx150x_regmap_bus = {
+	.reg_read  = sx150x_regmap_reg_read,
+	.reg_write = sx150x_regmap_reg_write,
+};
+
+static struct gpio_ops sx150x_gpio_ops = {
+	.direction_input   = sx150x_gpio_direction_input,
+	.direction_output  = sx150x_gpio_direction_output,
+	.get_direction	   = sx150x_gpio_get_direction,
+	.get		   = sx150x_gpio_get,
+	.set		   = sx150x_gpio_set,
+};
+
+static int sx150x_probe(struct device_d *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct sx150x_gpio *sx150x;
+	const struct sx150x_device_data *data;
+
+	data = of_device_get_match_data(dev);
+	if (!data)
+		return -EINVAL;
+
+	sx150x = xzalloc(sizeof(*sx150x));
+
+	sx150x->regmap = regmap_init(dev, &sx150x_regmap_bus,
+				     sx150x, &sx150x_regmap_config);
+	sx150x->client = client;
+	sx150x->data = data;
+	sx150x->gpio.ops   = &sx150x_gpio_ops;
+	sx150x->gpio.base  = -1;
+	sx150x->gpio.ngpio = sx150x->data->ngpios;
+	sx150x->gpio.dev   = &client->dev;
+
+	return gpiochip_add(&sx150x->gpio);
+}
+
+static __maybe_unused struct of_device_id sx150x_dt_ids[] = {
+	{ .compatible = "semtech,sx1503q", .data = &sx1503q_device_data, },
+	{ }
+};
+
+static struct driver_d sx150x_driver = {
+	.name = "sx150x",
+	.probe = sx150x_probe,
+	.of_compatible = sx150x_dt_ids,
+};
+
+static int __init sx150x_init(void)
+{
+	return i2c_driver_register(&sx150x_driver);
+}
+device_initcall(sx150x_init);
-- 
2.5.5


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