gpio: Add support for the Xylon LogiCVC GPIOs

The LogiCVC display hardware block comes with GPIO capabilities
that must be exposed separately from the main driver (as GPIOs) for
use with regulators and panels. A syscon is used to share the same
regmap across the two drivers.

Add a minimalistic GPIO driver to drive these GPIOs, using a syscon
regmap when available.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://lore.kernel.org/r/20191203141243.251058-5-paul.kocialkowski@bootlin.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -312,6 +312,12 @@ config GPIO_IXP4XX
 	  IXP4xx series of chips.
 
 	  If unsure, say N.
+config GPIO_LOGICVC
+	tristate "Xylon LogiCVC GPIO support"
+	depends on MFD_SYSCON && OF
+	help
+	  Say yes here to support GPIO functionality of the Xylon LogiCVC
+	  programmable logic block.
 
 config GPIO_LOONGSON
 	bool "Loongson-2/3 GPIO support"

drivers/gpio/Makefile

@@ -69,6 +69,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
 obj-$(CONFIG_GPIO_IXP4XX)		+= gpio-ixp4xx.o
 obj-$(CONFIG_GPIO_JANZ_TTL)		+= gpio-janz-ttl.o
 obj-$(CONFIG_GPIO_KEMPLD)		+= gpio-kempld.o
+obj-$(CONFIG_GPIO_LOGICVC)		+= gpio-logicvc.o
 obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
 obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
 obj-$(CONFIG_GPIO_LP3943)		+= gpio-lp3943.o

drivers/gpio/gpio-logicvc.c

@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Bootlin
+ * Author: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+
+#define LOGICVC_CTRL_REG		0x40
+#define LOGICVC_CTRL_GPIO_SHIFT		11
+#define LOGICVC_CTRL_GPIO_BITS		5
+
+#define LOGICVC_POWER_CTRL_REG		0x78
+#define LOGICVC_POWER_CTRL_GPIO_SHIFT	0
+#define LOGICVC_POWER_CTRL_GPIO_BITS	4
+
+struct logicvc_gpio {
+	struct gpio_chip chip;
+	struct regmap *regmap;
+};
+
+static void logicvc_gpio_offset(struct logicvc_gpio *logicvc, unsigned offset,
+				unsigned int *reg, unsigned int *bit)
+{
+	if (offset >= LOGICVC_CTRL_GPIO_BITS) {
+		*reg = LOGICVC_POWER_CTRL_REG;
+
+		/* To the (virtual) power ctrl offset. */
+		offset -= LOGICVC_CTRL_GPIO_BITS;
+		/* To the actual bit offset in reg. */
+		offset += LOGICVC_POWER_CTRL_GPIO_SHIFT;
+	} else {
+		*reg = LOGICVC_CTRL_REG;
+
+		/* To the actual bit offset in reg. */
+		offset += LOGICVC_CTRL_GPIO_SHIFT;
+	}
+
+	*bit = BIT(offset);
+}
+
+static int logicvc_gpio_get(struct gpio_chip *chip, unsigned offset)
+{
+	struct logicvc_gpio *logicvc = gpiochip_get_data(chip);
+	unsigned int reg, bit, value;
+	int ret;
+
+	logicvc_gpio_offset(logicvc, offset, &reg, &bit);
+
+	ret = regmap_read(logicvc->regmap, reg, &value);
+	if (ret)
+		return ret;
+
+	return !!(value & bit);
+}
+
+static void logicvc_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+	struct logicvc_gpio *logicvc = gpiochip_get_data(chip);
+	unsigned int reg, bit;
+
+	logicvc_gpio_offset(logicvc, offset, &reg, &bit);
+
+	regmap_update_bits(logicvc->regmap, reg, bit, value ? bit : 0);
+}
+
+static int logicvc_gpio_direction_output(struct gpio_chip *chip,
+					 unsigned offset, int value)
+{
+	/* Pins are always configured as output, so just set the value. */
+	logicvc_gpio_set(chip, offset, value);
+
+	return 0;
+}
+
+static struct regmap_config logicvc_gpio_regmap_config = {
+	.reg_bits	= 32,
+	.val_bits	= 32,
+	.reg_stride	= 4,
+	.name		= "logicvc-gpio",
+};
+
+static int logicvc_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *of_node = dev->of_node;
+	struct logicvc_gpio *logicvc;
+	int ret;
+
+	logicvc = devm_kzalloc(dev, sizeof(*logicvc), GFP_KERNEL);
+	if (!logicvc)
+		return -ENOMEM;
+
+	/* Try to get regmap from parent first. */
+	logicvc->regmap = syscon_node_to_regmap(of_node->parent);
+
+	/* Grab our own regmap if that fails. */
+	if (IS_ERR(logicvc->regmap)) {
+		struct resource res;
+		void __iomem *base;
+
+		ret = of_address_to_resource(of_node, 0, &res);
+		if (ret) {
+			dev_err(dev, "Failed to get resource from address\n");
+			return ret;
+		}
+
+		base = devm_ioremap_resource(dev, &res);
+		if (IS_ERR(base)) {
+			dev_err(dev, "Failed to map I/O base\n");
+			return PTR_ERR(base);
+		}
+
+		logicvc_gpio_regmap_config.max_register = resource_size(&res) -
+			logicvc_gpio_regmap_config.reg_stride;
+
+		logicvc->regmap =
+			devm_regmap_init_mmio(dev, base,
+					      &logicvc_gpio_regmap_config);
+		if (IS_ERR(logicvc->regmap)) {
+			dev_err(dev, "Failed to create regmap for I/O\n");
+			return PTR_ERR(logicvc->regmap);
+		}
+	}
+
+	logicvc->chip.parent = dev;
+	logicvc->chip.owner = THIS_MODULE;
+	logicvc->chip.label = dev_name(dev);
+	logicvc->chip.base = -1;
+	logicvc->chip.ngpio = LOGICVC_CTRL_GPIO_BITS +
+			      LOGICVC_POWER_CTRL_GPIO_BITS;
+	logicvc->chip.get = logicvc_gpio_get;
+	logicvc->chip.set = logicvc_gpio_set;
+	logicvc->chip.direction_output = logicvc_gpio_direction_output;
+
+	platform_set_drvdata(pdev, logicvc);
+
+	return devm_gpiochip_add_data(dev, &logicvc->chip, logicvc);
+}
+
+static const struct of_device_id logicivc_gpio_of_table[] = {
+	{
+		.compatible	= "xylon,logicvc-3.02.a-gpio",
+	},
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, logicivc_gpio_of_table);
+
+static struct platform_driver logicvc_gpio_driver = {
+	.driver	= {
+		.name		= "gpio-logicvc",
+		.of_match_table	= logicivc_gpio_of_table,
+	},
+	.probe	= logicvc_gpio_probe,
+};
+
+module_platform_driver(logicvc_gpio_driver);
+
+MODULE_AUTHOR("Paul Kocialkowski <paul.kocialkowski@bootlin.com>");
+MODULE_DESCRIPTION("Xylon LogiCVC GPIO driver");
+MODULE_LICENSE("GPL");