gpio: add Technologic I2C-FPGA gpio support

This driver is generic and aims to support all Technologic Systems's
boards embedding FPGA GPIOs with an I2C interface.

This driver supports TS-4900, TS-7970, TS-7990 and TS-4100 series.

Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -777,6 +777,13 @@ config GPIO_TPIC2810
 	  To compile this driver as a module, choose M here: the module will
 	  be called gpio-tpic2810.
 
+config GPIO_TS4900
+	tristate "Technologic Systems FPGA I2C GPIO"
+	select REGMAP_I2C
+	help
+	  Say yes here to enabled the GPIO driver for Technologic's FPGA core.
+	  Series supported include TS-4100, TS-4900, TS-7970 and TS-7990.
+
 endmenu
 
 menu "MFD GPIO expanders"

drivers/gpio/Makefile

@@ -112,6 +112,7 @@ obj-$(CONFIG_GPIO_TPS6586X)	+= gpio-tps6586x.o
 obj-$(CONFIG_GPIO_TPS65910)	+= gpio-tps65910.o
 obj-$(CONFIG_GPIO_TPS65912)	+= gpio-tps65912.o
 obj-$(CONFIG_GPIO_TS4800)	+= gpio-ts4800.o
+obj-$(CONFIG_GPIO_TS4900)	+= gpio-ts4900.o
 obj-$(CONFIG_GPIO_TS5500)	+= gpio-ts5500.o
 obj-$(CONFIG_GPIO_TWL4030)	+= gpio-twl4030.o
 obj-$(CONFIG_GPIO_TWL6040)	+= gpio-twl6040.o

drivers/gpio/gpio-ts4900.c

@@ -0,0 +1,190 @@
+/*
+ * Digital I/O driver for Technologic Systems I2C FPGA Core
+ *
+ * Copyright (C) 2015 Technologic Systems
+ * Copyright (C) 2016 Savoir-Faire Linux
+ *
+ * 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/gpio/driver.h>
+#include <linux/i2c.h>
+#include <linux/of_device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define DEFAULT_PIN_NUMBER	32
+/*
+ * Register bits used by the GPIO device
+ * Some boards, such as TS-7970 do not have a separate input bit
+ */
+#define TS4900_GPIO_OE		0x01
+#define TS4900_GPIO_OUT		0x02
+#define TS4900_GPIO_IN		0x04
+#define TS7970_GPIO_IN		0x02
+
+struct ts4900_gpio_priv {
+	struct regmap *regmap;
+	struct gpio_chip gpio_chip;
+	unsigned int input_bit;
+};
+
+static int ts4900_gpio_get_direction(struct gpio_chip *chip,
+				     unsigned int offset)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int reg;
+
+	regmap_read(priv->regmap, offset, &reg);
+
+	return !(reg & TS4900_GPIO_OE);
+}
+
+static int ts4900_gpio_direction_input(struct gpio_chip *chip,
+				       unsigned int offset)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+
+	/*
+	 * This will clear the output enable bit, the other bits are
+	 * dontcare when this is cleared
+	 */
+	return regmap_write(priv->regmap, offset, 0);
+}
+
+static int ts4900_gpio_direction_output(struct gpio_chip *chip,
+					unsigned int offset, int value)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+	int ret;
+
+	if (value)
+		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE |
+							 TS4900_GPIO_OUT);
+	else
+		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE);
+
+	return ret;
+}
+
+static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int reg;
+
+	regmap_read(priv->regmap, offset, &reg);
+
+	return !!(reg & priv->input_bit);
+}
+
+static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			    int value)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+
+	if (value)
+		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT,
+				   TS4900_GPIO_OUT);
+	else
+		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT, 0);
+}
+
+static const struct regmap_config ts4900_regmap_config = {
+	.reg_bits = 16,
+	.val_bits = 8,
+};
+
+static struct gpio_chip template_chip = {
+	.label			= "ts4900-gpio",
+	.owner			= THIS_MODULE,
+	.get_direction		= ts4900_gpio_get_direction,
+	.direction_input	= ts4900_gpio_direction_input,
+	.direction_output	= ts4900_gpio_direction_output,
+	.get			= ts4900_gpio_get,
+	.set			= ts4900_gpio_set,
+	.base			= -1,
+	.can_sleep		= true,
+};
+
+static const struct of_device_id ts4900_gpio_of_match_table[] = {
+	{
+		.compatible = "technologic,ts4900-gpio",
+		.data = (void *)TS4900_GPIO_IN,
+	}, {
+		.compatible = "technologic,ts7970-gpio",
+		.data = (void *)TS7970_GPIO_IN,
+	},
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, ts4900_gpio_of_match_table);
+
+static int ts4900_gpio_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	const struct of_device_id *match;
+	struct ts4900_gpio_priv *priv;
+	u32 ngpio;
+	int ret;
+
+	match = of_match_device(ts4900_gpio_of_match_table, &client->dev);
+	if (!match)
+		return -EINVAL;
+
+	if (of_property_read_u32(client->dev.of_node, "ngpios", &ngpio))
+		ngpio = DEFAULT_PIN_NUMBER;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->gpio_chip = template_chip;
+	priv->gpio_chip.label = "ts4900-gpio";
+	priv->gpio_chip.ngpio = ngpio;
+	priv->gpio_chip.parent = &client->dev;
+	priv->input_bit = (uintptr_t)match->data;
+
+	priv->regmap = devm_regmap_init_i2c(client, &ts4900_regmap_config);
+	if (IS_ERR(priv->regmap)) {
+		ret = PTR_ERR(priv->regmap);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = devm_gpiochip_add_data(&client->dev, &priv->gpio_chip, priv);
+	if (ret < 0) {
+		dev_err(&client->dev, "Unable to register gpiochip\n");
+		return ret;
+	}
+
+	i2c_set_clientdata(client, priv);
+
+	return 0;
+}
+
+static const struct i2c_device_id ts4900_gpio_id_table[] = {
+	{ "ts4900-gpio", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);
+
+static struct i2c_driver ts4900_gpio_driver = {
+	.driver = {
+		.name = "ts4900-gpio",
+		.of_match_table = ts4900_gpio_of_match_table,
+	},
+	.probe = ts4900_gpio_probe,
+	.id_table = ts4900_gpio_id_table,
+};
+module_i2c_driver(ts4900_gpio_driver);
+
+MODULE_AUTHOR("Technologic Systems");
+MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
+MODULE_LICENSE("GPL");