gpio: Add Delta TN48M CPLD GPIO driver

Delta TN48M switch has an onboard Lattice CPLD that is used as a GPIO
expander.

The CPLD provides 12 pins in total on the TN48M, but on more advanced
switch models it provides up to 192 pins, so the driver is extendable
to support more switches.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://lore.kernel.org/r/20220131133049.77780-3-robert.marko@sartura.hr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpio/Kconfig

@@ -1346,6 +1346,18 @@ config GPIO_TIMBERDALE
 	help
 	Add support for the GPIO IP in the timberdale FPGA.
 
+config GPIO_TN48M_CPLD
+	tristate "Delta Networks TN48M switch CPLD GPIO driver"
+	depends on MFD_TN48M_CPLD
+	select GPIO_REGMAP
+	help
+	  This enables support for the GPIOs found on the Delta
+	  Networks TN48M switch Lattice CPLD. It provides 12 pins in total,
+	  they are input-only or output-only type.
+
+	  This driver can also be built as a module. If so, the
+	  module will be called gpio-tn48m.
+
 config GPIO_TPS65086
 	tristate "TI TPS65086 GPO"
 	depends on MFD_TPS65086

drivers/gpio/Makefile

@@ -148,6 +148,7 @@ obj-$(CONFIG_GPIO_TEGRA186)		+= gpio-tegra186.o
 obj-$(CONFIG_GPIO_TEGRA)		+= gpio-tegra.o
 obj-$(CONFIG_GPIO_THUNDERX)		+= gpio-thunderx.o
 obj-$(CONFIG_GPIO_TIMBERDALE)		+= gpio-timberdale.o
+obj-$(CONFIG_GPIO_TN48M_CPLD)		+= gpio-tn48m.o
 obj-$(CONFIG_GPIO_TPIC2810)		+= gpio-tpic2810.o
 obj-$(CONFIG_GPIO_TPS65086)		+= gpio-tps65086.o
 obj-$(CONFIG_GPIO_TPS65218)		+= gpio-tps65218.o

drivers/gpio/gpio-tn48m.c

@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Delta TN48M CPLD GPIO driver
+ *
+ * Copyright (C) 2021 Sartura Ltd.
+ *
+ * Author: Robert Marko <robert.marko@sartura.hr>
+ */
+
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/regmap.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+enum tn48m_gpio_type {
+	TN48M_GP0 = 1,
+	TN48M_GPI,
+};
+
+struct tn48m_gpio_config {
+	int ngpio;
+	int ngpio_per_reg;
+	enum tn48m_gpio_type type;
+};
+
+static const struct tn48m_gpio_config tn48m_gpo_config = {
+	.ngpio = 4,
+	.ngpio_per_reg = 4,
+	.type = TN48M_GP0,
+};
+
+static const struct tn48m_gpio_config tn48m_gpi_config = {
+	.ngpio = 4,
+	.ngpio_per_reg = 4,
+	.type = TN48M_GPI,
+};
+
+static int tn48m_gpio_probe(struct platform_device *pdev)
+{
+	const struct tn48m_gpio_config *gpio_config;
+	struct gpio_regmap_config config = {};
+	struct regmap *regmap;
+	u32 base;
+	int ret;
+
+	if (!pdev->dev.parent)
+		return -ENODEV;
+
+	gpio_config = device_get_match_data(&pdev->dev);
+	if (!gpio_config)
+		return -ENODEV;
+
+	ret = device_property_read_u32(&pdev->dev, "reg", &base);
+	if (ret)
+		return ret;
+
+	regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!regmap)
+		return -ENODEV;
+
+	config.regmap = regmap;
+	config.parent = &pdev->dev;
+	config.ngpio = gpio_config->ngpio;
+	config.ngpio_per_reg = gpio_config->ngpio_per_reg;
+	switch (gpio_config->type) {
+	case TN48M_GP0:
+		config.reg_set_base = base;
+		break;
+	case TN48M_GPI:
+		config.reg_dat_base = base;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(&pdev->dev, &config));
+}
+
+static const struct of_device_id tn48m_gpio_of_match[] = {
+	{ .compatible = "delta,tn48m-gpo", .data = &tn48m_gpo_config },
+	{ .compatible = "delta,tn48m-gpi", .data = &tn48m_gpi_config },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tn48m_gpio_of_match);
+
+static struct platform_driver tn48m_gpio_driver = {
+	.driver = {
+		.name = "delta-tn48m-gpio",
+		.of_match_table = tn48m_gpio_of_match,
+	},
+	.probe = tn48m_gpio_probe,
+};
+module_platform_driver(tn48m_gpio_driver);
+
+MODULE_AUTHOR("Robert Marko <robert.marko@sartura.hr>");
+MODULE_DESCRIPTION("Delta TN48M CPLD GPIO driver");
+MODULE_LICENSE("GPL");