[PATCH] gpio: add driver for SAMA5D2 PIOBU pins

[Alexander Shiyan <eagle.alexander923@gmail.com>]

PIOBU pins do not lose their voltage during Backup/Self-refresh.
This patch adds a simple GPIO controller for them and a
maintainer for the driver.
This driver adds support for using the pins as GPIO
offering the possibility to read/set the voltage.

Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
---
 drivers/gpio/Kconfig              |  11 ++
 drivers/gpio/Makefile             |   1 +
 drivers/gpio/gpio-sama5d2-piobu.c | 238 ++++++++++++++++++++++++++++++
 3 files changed, 250 insertions(+)
 create mode 100644 drivers/gpio/gpio-sama5d2-piobu.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 76b11d93aa..dd95e8906b 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -177,6 +177,17 @@ config GPIO_ROCKCHIP
 	  Say yes here to include the driver for the GPIO controller found on
 	  Rockchip SoCs.
 
+config GPIO_SAMA5D2_PIOBU
+	bool "SAMA5D2 PIOBU GPIO support"
+	depends on MFD_SYSCON
+	depends on OF_GPIO
+	depends on ARCH_AT91 || COMPILE_TEST
+	help
+	  Say yes here to use the PIOBU pins as GPIOs.
+	  PIOBU pins on the SAMA5D2 can be used as GPIOs.
+	  The difference from regular GPIOs is that they
+	  maintain their value during backup/self-refresh.
+
 config GPIO_STMPE
 	depends on MFD_STMPE
 	bool "STMPE GPIO Expander"
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index b0575ccf8c..8560e1f059 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_GPIO_OMAP)		+= gpio-omap.o
 obj-$(CONFIG_GPIO_PCA953X)	+= gpio-pca953x.o
 obj-$(CONFIG_GPIO_PCF857X)	+= gpio-pcf857x.o
 obj-$(CONFIG_GPIO_PL061)	+= gpio-pl061.o
+obj-$(CONFIG_GPIO_SAMA5D2_PIOBU) += gpio-sama5d2-piobu.o
 obj-$(CONFIG_GPIO_STMPE)	+= gpio-stmpe.o
 obj-$(CONFIG_GPIO_ROCKCHIP)	+= gpio-rockchip.o
 obj-$(CONFIG_GPIO_TEGRA)	+= gpio-tegra.o
diff --git a/drivers/gpio/gpio-sama5d2-piobu.c b/drivers/gpio/gpio-sama5d2-piobu.c
new file mode 100644
index 0000000000..1de235ee8d
--- /dev/null
+++ b/drivers/gpio/gpio-sama5d2-piobu.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SAMA5D2 PIOBU GPIO controller
+ *
+ * Copyright (C) 2018 Microchip Technology Inc. and its subsidiaries
+ *
+ * Author: Andrei Stefanescu <andrei.stefanescu@microchip.com>
+ *
+ */
+#include <common.h>
+#include <gpio.h>
+#include <linux/regmap.h>
+#include <mfd/syscon.h>
+
+#define PIOBU_NUM 8
+#define PIOBU_REG_SIZE 4
+
+/*
+ * backup mode protection register for tamper detection
+ * normal mode protection register for tamper detection
+ * wakeup signal generation
+ */
+#define PIOBU_BMPR 0x7C
+#define PIOBU_NMPR 0x80
+#define PIOBU_WKPR 0x90
+
+#define PIOBU_BASE 0x18 /* PIOBU offset from SECUMOD base register address. */
+
+#define PIOBU_DET_OFFSET 16
+
+/* In the datasheet this bit is called OUTPUT */
+#define PIOBU_DIRECTION BIT(8)
+#define PIOBU_OUT BIT(8)
+#define PIOBU_IN 0
+
+#define PIOBU_SOD BIT(9)
+#define PIOBU_PDS BIT(10)
+
+#define PIOBU_HIGH BIT(9)
+#define PIOBU_LOW 0
+
+struct sama5d2_piobu {
+	struct gpio_chip chip;
+	struct regmap *regmap;
+};
+
+/*
+ * sama5d2_piobu_setup_pin() - prepares a pin for set_direction call
+ *
+ * Do not consider pin for tamper detection (normal and backup modes)
+ * Do not consider pin as tamper wakeup interrupt source
+ */
+static int sama5d2_piobu_setup_pin(struct gpio_chip *chip, unsigned int pin)
+{
+	int ret;
+	struct sama5d2_piobu *piobu = container_of(chip, struct sama5d2_piobu,
+						   chip);
+	unsigned int mask = BIT(PIOBU_DET_OFFSET + pin);
+
+	ret = regmap_update_bits(piobu->regmap, PIOBU_BMPR, mask, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(piobu->regmap, PIOBU_NMPR, mask, 0);
+	if (ret)
+		return ret;
+
+	return regmap_update_bits(piobu->regmap, PIOBU_WKPR, mask, 0);
+}
+
+/*
+ * sama5d2_piobu_write_value() - writes value & mask at the pin's PIOBU register
+ */
+static int sama5d2_piobu_write_value(struct gpio_chip *chip, unsigned int pin,
+				     unsigned int mask, unsigned int value)
+{
+	int reg;
+	struct sama5d2_piobu *piobu = container_of(chip, struct sama5d2_piobu,
+						   chip);
+
+	reg = PIOBU_BASE + pin * PIOBU_REG_SIZE;
+
+	return regmap_update_bits(piobu->regmap, reg, mask, value);
+}
+
+/*
+ * sama5d2_piobu_read_value() - read the value with masking from the pin's PIOBU
+ *			      register
+ */
+static int sama5d2_piobu_read_value(struct gpio_chip *chip, unsigned int pin,
+				    unsigned int mask)
+{
+	struct sama5d2_piobu *piobu = container_of(chip, struct sama5d2_piobu,
+						   chip);
+	unsigned int val, reg;
+	int ret;
+
+	reg = PIOBU_BASE + pin * PIOBU_REG_SIZE;
+	ret = regmap_read(piobu->regmap, reg, &val);
+	if (ret < 0)
+		return ret;
+
+	return val & mask;
+}
+
+/*
+ * sama5d2_piobu_get_direction() - gpiochip get_direction
+ */
+static int sama5d2_piobu_get_direction(struct gpio_chip *chip,
+				       unsigned int pin)
+{
+	int ret = sama5d2_piobu_read_value(chip, pin, PIOBU_DIRECTION);
+
+	if (ret < 0)
+		return ret;
+
+	return (ret == PIOBU_IN) ? GPIOF_DIR_IN : GPIOF_DIR_OUT;
+}
+
+/*
+ * sama5d2_piobu_direction_input() - gpiochip direction_input
+ */
+static int sama5d2_piobu_direction_input(struct gpio_chip *chip,
+					 unsigned int pin)
+{
+	return sama5d2_piobu_write_value(chip, pin, PIOBU_DIRECTION, PIOBU_IN);
+}
+
+/*
+ * sama5d2_piobu_direction_output() - gpiochip direction_output
+ */
+static int sama5d2_piobu_direction_output(struct gpio_chip *chip,
+					  unsigned int pin, int value)
+{
+	unsigned int val = PIOBU_OUT;
+
+	if (value)
+		val |= PIOBU_HIGH;
+
+	return sama5d2_piobu_write_value(chip, pin, PIOBU_DIRECTION | PIOBU_SOD,
+					 val);
+}
+
+/*
+ * sama5d2_piobu_get() - gpiochip get
+ */
+static int sama5d2_piobu_get(struct gpio_chip *chip, unsigned int pin)
+{
+	/* if pin is input, read value from PDS else read from SOD */
+	int ret = sama5d2_piobu_get_direction(chip, pin);
+
+	if (ret == GPIOF_DIR_IN)
+		ret = sama5d2_piobu_read_value(chip, pin, PIOBU_PDS);
+	else if (ret == GPIOF_DIR_OUT)
+		ret = sama5d2_piobu_read_value(chip, pin, PIOBU_SOD);
+
+	if (ret < 0)
+		return ret;
+
+	return !!ret;
+}
+
+/*
+ * sama5d2_piobu_set() - gpiochip set
+ */
+static void sama5d2_piobu_set(struct gpio_chip *chip, unsigned int pin,
+			      int value)
+{
+	if (!value)
+		value = PIOBU_LOW;
+	else
+		value = PIOBU_HIGH;
+
+	sama5d2_piobu_write_value(chip, pin, PIOBU_SOD, value);
+}
+
+static struct gpio_ops sama5d2_piobu_ops = {
+	.direction_input = sama5d2_piobu_direction_input,
+	.direction_output = sama5d2_piobu_direction_output,
+	.get = sama5d2_piobu_get,
+	.set = sama5d2_piobu_set,
+	.get_direction = sama5d2_piobu_get_direction,
+};
+
+static int sama5d2_piobu_probe(struct device *dev)
+{
+	struct sama5d2_piobu *piobu;
+	int ret, i;
+
+	piobu = kzalloc(sizeof(*piobu), GFP_KERNEL);
+	if (!piobu)
+		return -ENOMEM;
+
+	piobu->chip.base = -1;
+	piobu->chip.ops = &sama5d2_piobu_ops;
+	piobu->chip.ngpio = PIOBU_NUM;
+	piobu->chip.dev = dev;
+
+	piobu->regmap = syscon_node_to_regmap(dev->of_node);
+	if (IS_ERR(piobu->regmap)) {
+		dev_err(dev, "Failed to get syscon regmap %ld\n",
+			PTR_ERR(piobu->regmap));
+		return PTR_ERR(piobu->regmap);
+	}
+
+	ret = gpiochip_add(&piobu->chip);
+	if (ret) {
+		dev_err(dev, "Failed to add gpiochip %d\n", ret);
+		return ret;
+	}
+
+	for (i = 0; i < PIOBU_NUM; ++i) {
+		ret = sama5d2_piobu_setup_pin(&piobu->chip, i);
+		if (ret) {
+			dev_err(dev, "Failed to setup pin: %d %d\n", i, ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static const struct of_device_id sama5d2_piobu_ids[] = {
+	{ .compatible = "atmel,sama5d2-secumod" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sama5d2_piobu_ids);
+
+static struct driver sama5d2_piobu_driver = {
+	.name = "sama5d2-piobu",
+	.of_compatible = DRV_OF_COMPAT(sama5d2_piobu_ids),
+	.probe = sama5d2_piobu_probe,
+};
+coredevice_platform_driver(sama5d2_piobu_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("SAMA5D2 PIOBU controller driver");
+MODULE_AUTHOR("Andrei Stefanescu <andrei.stefanescu@microchip.com>");
-- 
2.39.1