gpio: New driver for LSI ZEVIO SoCs

This driver supports the GPIO controller found in LSI ZEVIO SoCs.
It has been successfully tested on a TI nspire CX calculator.

Signed-off-by: Fabian Vogt <fabian@ritter-vogt.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

3 files changed, 227 insertions, 0 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 3bddd36d2d12..5e8bd21240a1 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -145,6 +145,12 @@ config GPIO_EP93XX
         depends on ARCH_EP93XX
         select GPIO_GENERIC
 
+config GPIO_ZEVIO
+        bool "LSI ZEVIO SoC memory mapped GPIOs"
+        depends on OF
+        help
+          Say yes here to support the GPIO controller in LSI ZEVIO SoCs.
+
 config GPIO_MM_LANTIQ
         bool "Lantiq Memory mapped GPIOs"
         depends on LANTIQ && SOC_XWAY
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 5d50179ece16..b8453750e502 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -99,3 +99,4 @@ obj-$(CONFIG_GPIO_WM8350)	+= gpio-wm8350.o
 obj-$(CONFIG_GPIO_WM8994)       += gpio-wm8994.o
 obj-$(CONFIG_GPIO_XILINX)       += gpio-xilinx.o
 obj-$(CONFIG_GPIO_XTENSA)       += gpio-xtensa.o
+obj-$(CONFIG_GPIO_ZEVIO)        += gpio-zevio.o
diff --git a/drivers/gpio/gpio-zevio.c b/drivers/gpio/gpio-zevio.c
new file mode 100644
index 000000000000..9bf5034b6cdb
--- /dev/null
+++ b/drivers/gpio/gpio-zevio.c
@@ -0,0 +1,220 @@
+/*
+ * GPIO controller in LSI ZEVIO SoCs.
+ *
+ * Author: Fabian Vogt <fabian@ritter-vogt.de>
+ *
+ * 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/spinlock.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include <linux/slab.h>
+#include <linux/gpio.h>
+
+/*
+ * Memory layout:
+ * This chip has four gpio sections, each controls 8 GPIOs.
+ * Bit 0 in section 0 is GPIO 0, bit 2 in section 1 is GPIO 10.
+ * Disclaimer: Reverse engineered!
+ * For more information refer to:
+ * http://hackspire.unsads.com/wiki/index.php/Memory-mapped_I/O_ports#90000000_-_General_Purpose_I.2FO_.28GPIO.29
+ *
+ * 0x00-0x3F: Section 0
+ *     +0x00: Masked interrupt status (read-only)
+ *     +0x04: R: Interrupt status W: Reset interrupt status
+ *     +0x08: R: Interrupt mask W: Mask interrupt
+ *     +0x0C: W: Unmask interrupt (write-only)
+ *     +0x10: Direction: I/O=1/0
+ *     +0x14: Output
+ *     +0x18: Input (read-only)
+ *     +0x20: R: Level interrupt W: Set as level interrupt
+ * 0x40-0x7F: Section 1
+ * 0x80-0xBF: Section 2
+ * 0xC0-0xFF: Section 3
+ */
+
+#define ZEVIO_GPIO_SECTION_SIZE                 0x40
+
+/* Offsets to various registers */
+#define ZEVIO_GPIO_INT_MASKED_STATUS    0x00
+#define ZEVIO_GPIO_INT_STATUS           0x04
+#define ZEVIO_GPIO_INT_UNMASK           0x08
+#define ZEVIO_GPIO_INT_MASK             0x0C
+#define ZEVIO_GPIO_DIRECTION            0x10
+#define ZEVIO_GPIO_OUTPUT               0x14
+#define ZEVIO_GPIO_INPUT                        0x18
+#define ZEVIO_GPIO_INT_STICKY           0x20
+
+#define to_zevio_gpio(chip) container_of(to_of_mm_gpio_chip(chip), \
+                                struct zevio_gpio, chip)
+
+/* Bit number of GPIO in its section */
+#define ZEVIO_GPIO_BIT(gpio) (gpio&7)
+
+struct zevio_gpio {
+        spinlock_t              lock;
+        struct of_mm_gpio_chip  chip;
+};
+
+static inline u32 zevio_gpio_port_get(struct zevio_gpio *c, unsigned pin,
+                                        unsigned port_offset)
+{
+        unsigned section_offset = ((pin >> 3) & 3)*ZEVIO_GPIO_SECTION_SIZE;
+        return readl(IOMEM(c->chip.regs + section_offset + port_offset));
+}
+
+static inline void zevio_gpio_port_set(struct zevio_gpio *c, unsigned pin,
+                                        unsigned port_offset, u32 val)
+{
+        unsigned section_offset = ((pin >> 3) & 3)*ZEVIO_GPIO_SECTION_SIZE;
+        writel(val, IOMEM(c->chip.regs + section_offset + port_offset));
+}
+
+/* Functions for struct gpio_chip */
+static int zevio_gpio_get(struct gpio_chip *chip, unsigned pin)
+{
+        struct zevio_gpio *controller = to_zevio_gpio(chip);
+
+        /* Only reading allowed, so no spinlock needed */
+        u32 val = zevio_gpio_port_get(controller, pin, ZEVIO_GPIO_INPUT);
+
+        return (val >> ZEVIO_GPIO_BIT(pin)) & 0x1;
+}
+
+static void zevio_gpio_set(struct gpio_chip *chip, unsigned pin, int value)
+{
+        struct zevio_gpio *controller = to_zevio_gpio(chip);
+        u32 val;
+
+        spin_lock(&controller->lock);
+        val = zevio_gpio_port_get(controller, pin, ZEVIO_GPIO_OUTPUT);
+        if (value)
+                val |= BIT(ZEVIO_GPIO_BIT(pin));
+        else
+                val &= ~BIT(ZEVIO_GPIO_BIT(pin));
+
+        zevio_gpio_port_set(controller, pin, ZEVIO_GPIO_OUTPUT, val);
+        spin_unlock(&controller->lock);
+}
+
+static int zevio_gpio_direction_input(struct gpio_chip *chip, unsigned pin)
+{
+        struct zevio_gpio *controller = to_zevio_gpio(chip);
+        u32 val;
+
+        spin_lock(&controller->lock);
+
+        val = zevio_gpio_port_get(controller, pin, ZEVIO_GPIO_DIRECTION);
+        val |= BIT(ZEVIO_GPIO_BIT(pin));
+        zevio_gpio_port_set(controller, pin, ZEVIO_GPIO_DIRECTION, val);
+
+        spin_unlock(&controller->lock);
+
+        return 0;
+}
+
+static int zevio_gpio_direction_output(struct gpio_chip *chip,
+                                       unsigned pin, int value)
+{
+        struct zevio_gpio *controller = to_zevio_gpio(chip);
+        u32 val;
+
+        spin_lock(&controller->lock);
+        val = zevio_gpio_port_get(controller, pin, ZEVIO_GPIO_OUTPUT);
+        if (value)
+                val |= BIT(ZEVIO_GPIO_BIT(pin));
+        else
+                val &= ~BIT(ZEVIO_GPIO_BIT(pin));
+
+        zevio_gpio_port_set(controller, pin, ZEVIO_GPIO_OUTPUT, val);
+        val = zevio_gpio_port_get(controller, pin, ZEVIO_GPIO_DIRECTION);
+        val &= ~BIT(ZEVIO_GPIO_BIT(pin));
+        zevio_gpio_port_set(controller, pin, ZEVIO_GPIO_DIRECTION, val);
+
+        spin_unlock(&controller->lock);
+
+        return 0;
+}
+
+static int zevio_gpio_to_irq(struct gpio_chip *chip, unsigned pin)
+{
+        /*
+         * TODO: Implement IRQs.
+         * Not implemented yet due to weird lockups
+         */
+
+        return -ENXIO;
+}
+
+static struct gpio_chip zevio_gpio_chip = {
+        .direction_input        = zevio_gpio_direction_input,
+        .direction_output       = zevio_gpio_direction_output,
+        .set                    = zevio_gpio_set,
+        .get                    = zevio_gpio_get,
+        .to_irq                 = zevio_gpio_to_irq,
+        .base                   = 0,
+        .owner                  = THIS_MODULE,
+        .ngpio                  = 32,
+        .of_gpio_n_cells        = 2,
+};
+
+/* Initialization */
+static int zevio_gpio_probe(struct platform_device *pdev)
+{
+        struct zevio_gpio *controller;
+        int status, i;
+
+        controller = devm_kzalloc(&pdev->dev, sizeof(*controller), GFP_KERNEL);
+        if (!controller) {
+                dev_err(&pdev->dev, "not enough free memory\n");
+                return -ENOMEM;
+        }
+
+        /* Copy our reference */
+        controller->chip.gc = zevio_gpio_chip;
+        controller->chip.gc.dev = &pdev->dev;
+
+        status = of_mm_gpiochip_add(pdev->dev.of_node, &(controller->chip));
+        if (status) {
+                dev_err(&pdev->dev, "failed to add gpiochip: %d\n", status);
+                return status;
+        }
+
+        spin_lock_init(&controller->lock);
+
+        /* Disable interrupts, they only cause errors */
+        for (i = 0; i < controller->chip.gc.ngpio; i += 8)
+                zevio_gpio_port_set(controller, i, ZEVIO_GPIO_INT_MASK, 0xFF);
+
+        dev_dbg(controller->chip.gc.dev, "ZEVIO GPIO controller set up!\n");
+
+        return 0;
+}
+
+static struct of_device_id zevio_gpio_of_match[] = {
+        { .compatible = "lsi,zevio-gpio", },
+        { },
+};
+
+MODULE_DEVICE_TABLE(of, zevio_gpio_of_match);
+
+static struct platform_driver zevio_gpio_driver = {
+        .driver         = {
+                .name   = "gpio-zevio",
+                .owner  = THIS_MODULE,
+                .of_match_table = of_match_ptr(zevio_gpio_of_match),
+        },
+        .probe          = zevio_gpio_probe,
+};
+module_platform_driver(zevio_gpio_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Fabian Vogt <fabian@ritter-vogt.de>");
+MODULE_DESCRIPTION("LSI ZEVIO SoC GPIO driver");