gpio: ds4520: Add ADI DS4520 GPIO Expander Support

The DS4520 is a 9-bit nonvolatile (NV) I/O expander.
It offers users a digitally programmable alternative
to hardware jumpers and mechanical switches that are
being used to control digital logic node.

Signed-off-by: Okan Sahin <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/Kconfig

···
 	  To compile this driver as a module, choose M here: the module will
 	  be called gpio-fxl6408.
 
+config GPIO_DS4520
+	tristate "DS4520 I2C GPIO expander"
+	select REGMAP_I2C
+	select GPIO_REGMAP
+	help
+	  GPIO driver for ADI DS4520 I2C-based GPIO expander.
+	  Say yes here to enable the GPIO driver for the ADI DS4520 chip.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gpio-ds4520.
+
 config GPIO_GW_PLD
 	tristate "Gateworks PLD GPIO Expander"
 	depends on OF_GPIO

drivers/gpio/Makefile

···
 obj-$(CONFIG_GPIO_DA9055)		+= gpio-da9055.o
 obj-$(CONFIG_GPIO_DAVINCI)		+= gpio-davinci.o
 obj-$(CONFIG_GPIO_DLN2)			+= gpio-dln2.o
+obj-$(CONFIG_GPIO_DS4520)		+= gpio-ds4520.o
 obj-$(CONFIG_GPIO_DWAPB)		+= gpio-dwapb.o
 obj-$(CONFIG_GPIO_EIC_SPRD)		+= gpio-eic-sprd.o
 obj-$(CONFIG_GPIO_ELKHARTLAKE)		+= gpio-elkhartlake.o

drivers/gpio/gpio-ds4520.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Analog Devices, Inc.
+ * Driver for the DS4520 I/O Expander
+ */
+
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/regmap.h>
+#include <linux/i2c.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define DS4520_PULLUP0		0xF0
+#define DS4520_IO_CONTROL0	0xF2
+#define DS4520_IO_STATUS0	0xF8
+
+static const struct regmap_config ds4520_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int ds4520_gpio_probe(struct i2c_client *client)
+{
+	struct gpio_regmap_config config = { };
+	struct device *dev = &client->dev;
+	struct regmap *regmap;
+	u32 ngpio;
+	u32 base;
+	int ret;
+
+	ret = device_property_read_u32(dev, "reg", &base);
+	if (ret)
+		return dev_err_probe(dev, ret, "Missing 'reg' property.\n");
+
+	ret = device_property_read_u32(dev, "ngpios", &ngpio);
+	if (ret)
+		return dev_err_probe(dev, ret, "Missing 'ngpios' property.\n");
+
+	regmap = devm_regmap_init_i2c(client, &ds4520_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to allocate register map\n");
+
+	config.regmap = regmap;
+	config.parent = dev;
+	config.ngpio = ngpio;
+
+	config.reg_dat_base = base + DS4520_IO_STATUS0;
+	config.reg_set_base = base + DS4520_PULLUP0;
+	config.reg_dir_out_base = base + DS4520_IO_CONTROL0;
+
+	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &config));
+}
+
+static const struct of_device_id ds4520_gpio_of_match_table[] = {
+	{ .compatible = "adi,ds4520-gpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ds4520_gpio_of_match_table);
+
+static const struct i2c_device_id ds4520_gpio_id_table[] = {
+	{ "ds4520-gpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ds4520_gpio_id_table);
+
+static struct i2c_driver ds4520_gpio_driver = {
+	.driver = {
+		.name = "ds4520-gpio",
+		.of_match_table = ds4520_gpio_of_match_table,
+	},
+	.probe = ds4520_gpio_probe,
+	.id_table = ds4520_gpio_id_table,
+};
+module_i2c_driver(ds4520_gpio_driver);
+
+MODULE_DESCRIPTION("DS4520 I/O Expander");
+MODULE_AUTHOR("Okan Sahin <[e-mail]>");
+MODULE_LICENSE("GPL");