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+// SPDX-License-Identifier: GPL-2.0-or-later
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+/*
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+ * Driver for reset key gpio line on MikroTik RB91x board series.
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+ * This line is shared between NAND ALE (goes through a latch),
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+ * NAND IO7 and reset key. We make 3 virtual gpio lines from the
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+ * single physical one:
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+ * 1) Capable output one for NAND,
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+ * 2) Capable input one for reset key,
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+ * 3) And capable output one, aka "key-poll-disable",
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+ * for NAND -- to syncronise NAND operation and key polling.
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+ *
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+ * Copyright (C) 2021 Denis Kalashnikov <[email protected]>
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+ */
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+
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+#include <linux/kernel.h>
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+#include <linux/init.h>
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+#include <linux/module.h>
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+#include <linux/types.h>
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+#include <linux/gpio/consumer.h>
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+#include <linux/gpio/driver.h>
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+#include <linux/platform_device.h>
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+#include <linux/of_platform.h>
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+#include <linux/of_gpio.h>
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+#include <linux/delay.h>
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+
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+#define GPIO_RB91X_KEY_DRIVER_NAME "gpio-rb91x-key"
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+
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+enum gpio_rb91x_key_gpios {
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+ GPIO_RB91X_KEY_NAND,
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+ GPIO_RB91X_KEY_POLL,
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+ GPIO_RB91X_KEY_PDIS,
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+
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+ GPIO_RB91X_KEY_NGPIOS,
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+};
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+
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+struct gpio_rb91x_key {
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+ struct gpio_chip gc;
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+ struct mutex mutex;
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+ struct mutex poll_mutex;
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+ int polling_disabled;
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+ struct gpio_desc *gpio;
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+};
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+
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+static inline struct gpio_rb91x_key *to_gpio_rb91x_key(struct gpio_chip *gc)
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+{
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+ return container_of(gc, struct gpio_rb91x_key, gc);
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+}
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+
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+static int gpio_rb91x_key_get(struct gpio_chip *gc, unsigned offset)
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+{
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+ struct gpio_rb91x_key *drvdata = to_gpio_rb91x_key(gc);
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+ struct gpio_desc *gpio = drvdata->gpio;
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+ int val, bak_val;
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+
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+ switch (offset) {
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+ case GPIO_RB91X_KEY_NAND:
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+ mutex_lock(&drvdata->mutex);
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+ val = gpiod_get_value_cansleep(gpio);
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+ mutex_unlock(&drvdata->mutex);
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+ break;
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+ case GPIO_RB91X_KEY_PDIS:
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+ mutex_lock(&drvdata->mutex);
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+ val = drvdata->polling_disabled;
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+ mutex_unlock(&drvdata->mutex);
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+ break;
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+ case GPIO_RB91X_KEY_POLL:
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+ mutex_lock(&drvdata->poll_mutex);
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+ mutex_lock(&drvdata->mutex);
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+ bak_val = gpiod_get_raw_value_cansleep(gpio);
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+ gpiod_direction_input(gpio);
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+ /*
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+ * Without this delay nothing works. Get it
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+ * from mikrotik RouterOS linux kernel patches.
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+ */
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+ udelay(200);
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+ val = gpiod_get_raw_value_cansleep(gpio);
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+ gpiod_direction_output_raw(gpio, bak_val);
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+ mutex_unlock(&drvdata->mutex);
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+ mutex_unlock(&drvdata->poll_mutex);
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+ break;
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+ default:
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+ return -EINVAL;
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+ }
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+
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+ return val;
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+}
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+
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+static int gpio_rb91x_key_direction_input(struct gpio_chip *gc, unsigned offset)
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+{
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+ switch (offset) {
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+ case GPIO_RB91X_KEY_POLL:
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+ return 0;
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+ default:
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+ return -EINVAL;
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+ }
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+}
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+
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+static void gpio_rb91x_key_set(struct gpio_chip *gc, unsigned offset, int value)
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+{
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+ struct gpio_rb91x_key *drvdata = to_gpio_rb91x_key(gc);
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+ struct gpio_desc *gpio = drvdata->gpio;
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+
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+ mutex_lock(&drvdata->mutex);
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+
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+ switch (offset) {
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+ case GPIO_RB91X_KEY_NAND:
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+ gpiod_set_raw_value_cansleep(gpio, value);
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+ break;
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+ case GPIO_RB91X_KEY_PDIS:
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+ if (value) {
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+ if (!drvdata->polling_disabled) {
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+ mutex_lock(&drvdata->poll_mutex);
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+ drvdata->polling_disabled = 1;
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+ }
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+ } else {
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+ if (drvdata->polling_disabled) {
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+ mutex_unlock(&drvdata->poll_mutex);
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+ drvdata->polling_disabled = 0;
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+ }
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+ }
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+ break;
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+ default:
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+ break;
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+ }
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+
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+ mutex_unlock(&drvdata->mutex);
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+}
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+
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+static int gpio_rb91x_key_direction_output(struct gpio_chip *gc, unsigned offset,
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+ int value)
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+{
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+ switch (offset) {
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+ case GPIO_RB91X_KEY_NAND:
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+ case GPIO_RB91X_KEY_PDIS:
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+ gpio_rb91x_key_set(gc, offset, value);
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+ return 0;
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+ default:
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+ return -EINVAL;
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+ }
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+}
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+
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+static int gpio_rb91x_key_probe(struct platform_device *pdev)
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+{
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+ struct gpio_rb91x_key *drvdata;
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+ struct gpio_chip *gc;
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+ struct device *dev = &pdev->dev;
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+ struct device_node *of_node = dev->of_node;
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+ int r;
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+
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+ drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
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+ if (!drvdata)
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+ return -ENOMEM;
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+
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+ mutex_init(&drvdata->mutex);
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+ mutex_init(&drvdata->poll_mutex);
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+
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+ drvdata->gpio = devm_gpiod_get(dev, NULL, GPIOD_OUT_LOW);
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+ if (IS_ERR(drvdata->gpio)) {
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+ if (PTR_ERR(drvdata->gpio) != -EPROBE_DEFER) {
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+ dev_err(dev, "failed to get gpio: %ld\n",
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+ PTR_ERR(drvdata->gpio));
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+ }
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+ return PTR_ERR(drvdata->gpio);
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+ }
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+
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+ gc = &drvdata->gc;
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+ gc->label = GPIO_RB91X_KEY_DRIVER_NAME;
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+ gc->can_sleep = 1;
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+ gc->base = -1;
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+ gc->ngpio = GPIO_RB91X_KEY_NGPIOS;
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+ gc->get = gpio_rb91x_key_get;
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+ gc->set = gpio_rb91x_key_set;
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+ gc->direction_output = gpio_rb91x_key_direction_output;
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+ gc->direction_input = gpio_rb91x_key_direction_input;
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+ gc->of_node = of_node;
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+
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+ platform_set_drvdata(pdev, drvdata);
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+
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+ r = gpiochip_add(&drvdata->gc);
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+ if (r) {
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+ dev_err(dev, "gpiochip_add() failed: %d\n", r);
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+ return r;
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+ }
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+
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+ return 0;
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+}
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+
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+static int gpio_rb91x_key_remove(struct platform_device *pdev)
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+{
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+ struct gpio_rb91x_key *drvdata = platform_get_drvdata(pdev);
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+
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+ gpiochip_remove(&drvdata->gc);
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+ return 0;
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+}
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+
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+static const struct of_device_id gpio_rb91x_key_match[] = {
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+ { .compatible = "mikrotik,"GPIO_RB91X_KEY_DRIVER_NAME },
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+ {},
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+};
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+
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+MODULE_DEVICE_TABLE(of, gpio_rb91x_key_match);
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+
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+static struct platform_driver gpio_rb91x_key_driver = {
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+ .probe = gpio_rb91x_key_probe,
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+ .remove = gpio_rb91x_key_remove,
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+ .driver = {
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+ .name = GPIO_RB91X_KEY_DRIVER_NAME,
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+ .owner = THIS_MODULE,
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+ .of_match_table = gpio_rb91x_key_match,
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+ },
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+};
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+
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+module_platform_driver(gpio_rb91x_key_driver);
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+
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+MODULE_DESCRIPTION("Driver for reset key gpio line shared with NAND for MikroTik RB91x board series.");
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+MODULE_AUTHOR("Denis Kalashnikov <[email protected]>");
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+MODULE_LICENSE("GPL v2");
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+MODULE_ALIAS("platform:" GPIO_RB91X_KEY_DRIVER_NAME);
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Denis Kalashnikov