gpio: exar: add gpio for exar cards

Exar XR17V352/354/358 chips have 16 multi-purpose inputs/outputs which
can be controlled using gpio interface.

Add the gpio specific code.
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -185,6 +185,13 @@ config GPIO_ETRAXFS
 	help
 	  Say yes here to support the GPIO controller on Axis ETRAX FS SoCs.
 
+config GPIO_EXAR
+	tristate "Support for GPIO pins on XR17V352/354/358"
+	depends on SERIAL_8250_EXAR
+	help
+	  Selecting this option will enable handling of GPIO pins present
+	  on Exar XR17V352/354/358 chips.
+
 config GPIO_GE_FPGA
 	bool "GE FPGA based GPIO"
 	depends on GE_FPGA

drivers/gpio/Makefile

@@ -46,6 +46,7 @@ obj-$(CONFIG_GPIO_DWAPB)	+= gpio-dwapb.o
 obj-$(CONFIG_GPIO_EM)		+= gpio-em.o
 obj-$(CONFIG_GPIO_EP93XX)	+= gpio-ep93xx.o
 obj-$(CONFIG_GPIO_ETRAXFS)	+= gpio-etraxfs.o
+obj-$(CONFIG_GPIO_EXAR)		+= gpio-exar.o
 obj-$(CONFIG_GPIO_F7188X)	+= gpio-f7188x.o
 obj-$(CONFIG_GPIO_GE_FPGA)	+= gpio-ge.o
 obj-$(CONFIG_GPIO_GEMINI)	+= gpio-gemini.o

drivers/gpio/gpio-exar.c

+/*
+ * GPIO driver for Exar XR17V35X chip
+ *
+ * Copyright (C) 2015 Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
+ *
+ * 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.
+ */
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+
+#define EXAR_OFFSET_MPIOLVL_LO 0x90
+#define EXAR_OFFSET_MPIOSEL_LO 0x93
+#define EXAR_OFFSET_MPIOLVL_HI 0x96
+#define EXAR_OFFSET_MPIOSEL_HI 0x99
+
+#define DRIVER_NAME "gpio_exar"
+
+static DEFINE_IDA(ida_index);
+
+struct exar_gpio_chip {
+	struct gpio_chip gpio_chip;
+	struct mutex lock;
+	int index;
+	void __iomem *regs;
+	char name[20];
+};
+
+static void exar_update(struct gpio_chip *chip, unsigned int reg, int val,
+			unsigned int offset)
+{
+	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
+	int temp;
+
+	mutex_lock(&exar_gpio->lock);
+	temp = readb(exar_gpio->regs + reg);
+	temp &= ~BIT(offset);
+	if (val)
+		temp |= BIT(offset);
+	writeb(temp, exar_gpio->regs + reg);
+	mutex_unlock(&exar_gpio->lock);
+}
+
+static int exar_set_direction(struct gpio_chip *chip, int direction,
+			      unsigned int offset)
+{
+	unsigned int bank = offset / 8;
+	unsigned int addr;
+
+	addr = bank ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
+	exar_update(chip, addr, direction, offset % 8);
+	return 0;
+}
+
+static int exar_direction_output(struct gpio_chip *chip, unsigned int offset,
+				 int value)
+{
+	return exar_set_direction(chip, 0, offset);
+}
+
+static int exar_direction_input(struct gpio_chip *chip, unsigned int offset)
+{
+	return exar_set_direction(chip, 1, offset);
+}
+
+static int exar_get(struct gpio_chip *chip, unsigned int reg)
+{
+	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
+	int value;
+
+	mutex_lock(&exar_gpio->lock);
+	value = readb(exar_gpio->regs + reg);
+	mutex_unlock(&exar_gpio->lock);
+
+	return !!value;
+}
+
+static int exar_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+	unsigned int bank = offset / 8;
+	unsigned int addr;
+	int val;
+
+	addr = bank ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
+	val = exar_get(chip, addr) >> (offset % 8);
+
+	return !!val;
+}
+
+static int exar_get_value(struct gpio_chip *chip, unsigned int offset)
+{
+	unsigned int bank = offset / 8;
+	unsigned int addr;
+	int val;
+
+	addr = bank ? EXAR_OFFSET_MPIOLVL_LO : EXAR_OFFSET_MPIOLVL_HI;
+	val = exar_get(chip, addr) >> (offset % 8);
+
+	return !!val;
+}
+
+static void exar_set_value(struct gpio_chip *chip, unsigned int offset,
+			   int value)
+{
+	unsigned int bank = offset / 8;
+	unsigned int addr;
+
+	addr = bank ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
+	exar_update(chip, addr, value, offset % 8);
+}
+
+static int gpio_exar_probe(struct platform_device *pdev)
+{
+	struct pci_dev *pcidev = platform_get_drvdata(pdev);
+	struct exar_gpio_chip *exar_gpio;
+	void __iomem *p;
+	int index, ret;
+
+	if (pcidev->vendor != PCI_VENDOR_ID_EXAR)
+		return -ENODEV;
+
+	/*
+	 * Map the pci device to get the register addresses.
+	 * We will need to read and write those registers to control
+	 * the GPIO pins.
+	 * Using managed functions will save us from unmaping on exit.
+	 * As the device is enabled using managed functions by the
+	 * UART driver we can also use managed functions here.
+	 */
+	p = pcim_iomap(pcidev, 0, 0);
+	if (!p)
+		return -ENOMEM;
+
+	exar_gpio = devm_kzalloc(&pcidev->dev, sizeof(*exar_gpio), GFP_KERNEL);
+	if (!exar_gpio)
+		return -ENOMEM;
+
+	mutex_init(&exar_gpio->lock);
+
+	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);
+
+	sprintf(exar_gpio->name, "exar_gpio%d", index);
+	exar_gpio->gpio_chip.label = exar_gpio->name;
+	exar_gpio->gpio_chip.parent = &pcidev->dev;
+	exar_gpio->gpio_chip.direction_output = exar_direction_output;
+	exar_gpio->gpio_chip.direction_input = exar_direction_input;
+	exar_gpio->gpio_chip.get_direction = exar_get_direction;
+	exar_gpio->gpio_chip.get = exar_get_value;
+	exar_gpio->gpio_chip.set = exar_set_value;
+	exar_gpio->gpio_chip.base = -1;
+	exar_gpio->gpio_chip.ngpio = 16;
+	exar_gpio->regs = p;
+	exar_gpio->index = index;
+
+	ret = devm_gpiochip_add_data(&pcidev->dev,
+				     &exar_gpio->gpio_chip, exar_gpio);
+	if (ret)
+		goto err_destroy;
+
+	platform_set_drvdata(pdev, exar_gpio);
+
+	return 0;
+
+err_destroy:
+	ida_simple_remove(&ida_index, index);
+	mutex_destroy(&exar_gpio->lock);
+	return ret;
+}
+
+static int gpio_exar_remove(struct platform_device *pdev)
+{
+	struct exar_gpio_chip *exar_gpio = platform_get_drvdata(pdev);
+
+	ida_simple_remove(&ida_index, exar_gpio->index);
+	mutex_destroy(&exar_gpio->lock);
+
+	return 0;
+}
+
+static struct platform_driver gpio_exar_driver = {
+	.probe	= gpio_exar_probe,
+	.remove	= gpio_exar_remove,
+	.driver	= {
+		.name = DRIVER_NAME,
+	},
+};
+
+module_platform_driver(gpio_exar_driver);
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+MODULE_DESCRIPTION("Exar GPIO driver");
+MODULE_AUTHOR("Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>");
+MODULE_LICENSE("GPL");