@@ -0,0 +1,327 @@
+/*
+ * LTC2952 PowerPath TM driver
+ *
+ * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * ----------------------------------------
+ * - Description
+ * ----------------------------------------
+ *
+ * This driver is to be used with an external LTC2952 PowerPath Controller.
+ * Its function is to determine when a external shutdown is triggered and react
+ * by properly shutting down the system.
+ *
+ * This driver expects a device tree with a ltc2952 entry for pin mapping.
+ *
+ * ----------------------------------------
+ * - GPIO
+ * ----------------------------------------
+ *
+ * The following GPIOs are used:
+ * - trigger (input, optional)
+ * Input active indicates the shutdown trigger. If its state reverts to
+ * inactive within the timeout defined by trigger_delay, the system won't
+ * be shut down. If no pin is assigned to this input the driver will start
+ * the watchdog immediately and only a power off event will poweroff the
+ * ltc2952
+ *
+ * - watchdog (output)
+ * Once a shutdown is triggered, the driver will toggle this signal, with
+ * an internal (wde_interval) to stall the hardware shut down.
+ *
+ * - poweroff (output)
+ * The last action during shutdown is triggering this signalling, such
+ * that the PowerPath Control will power down the hardware.
+ *
+ * ----------------------------------------
+ * - Interrupts
+ * ----------------------------------------
+ *
+ * The driver requires a non-shared, edge-triggered interrupt on the trigger
+ * GPIO.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/ktime.h>
+#include <linux/slab.h>
+#include <linux/kmod.h>
+#include <linux/module.h>
+#include <linux/gpio/consumer.h>
+#include <linux/reboot.h>
+
+#define WDE_TIMEOUT ktime_set(0, 300L*1E6L)
+#define TRIGGER_TIMEOUT ktime_set(2, 500L*1E6L)
+
+struct ltc2952_poweroff {
+ struct hrtimer timer_trigger;
+ struct hrtimer timer_wde;
+
+ ktime_t trigger_delay;
+ ktime_t wde_interval;
+
+ struct device *dev;
+
+ struct gpio_desc *gpio_trigger;
+ struct gpio_desc *gpio_watchdog;
+ struct gpio_desc *gpio_poweroff;
+
+ bool kernel_panic;
+ struct notifier_block panic_notifier;
+};
+#define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
+
+/**
+ * ltc2952_poweroff_timer_wde - Timer callback
+ * Toggles the watchdog reset signal each wde_interval
+ *
+ * @timer: corresponding timer
+ *
+ * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
+ * machine actually shuts down
+ */
+static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
+{
+ ktime_t now;
+ int state;
+ struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
+
+ if (data->kernel_panic)
+ return HRTIMER_NORESTART;
+
+ state = gpiod_get_value(data->gpio_watchdog);
+ gpiod_set_value(data->gpio_watchdog, !state);
+
+ now = hrtimer_cb_get_time(timer);
+ hrtimer_forward(timer, now, data->wde_interval);
+
+ return HRTIMER_RESTART;
+}
+
+static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
+{
+ if (hrtimer_start(&data->timer_wde,
+ data->wde_interval, HRTIMER_MODE_REL)) {
+ /*
+ * The device will not toggle the watchdog reset,
+ * thus shut down is only safe if the PowerPath controller
+ * has a long enough time-off before triggering a hardware
+ * power-off.
+ *
+ * Only mention the error, as the system will power-off anyway
+ */
+ dev_err(data->dev, "unable to start the watchdog timer\n");
+ }
+}
+
+static enum hrtimer_restart ltc2952_poweroff_timer_trigger(struct hrtimer *t)
+{
+ struct ltc2952_poweroff *data = to_ltc2952(t, timer_trigger);
+
+ dev_info(data->dev, "executing shutdown\n");
+ ltc2952_poweroff_start_wde(data);
+ orderly_poweroff(true);
+ return HRTIMER_NORESTART;
+}
+
+/**
+ * ltc2952_poweroff_handler - Interrupt handler
+ *
+ * Activate or deactive the shutdown timeout, based on the value of the trigger
+ * gpio. If the button is pressed for long enough, the shutdown timer fires and
+ * the system is actually shut down.
+ *
+ * @irq: IRQ number
+ * @dev_id: pointer to the main data structure
+ */
+static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
+{
+ struct ltc2952_poweroff *data = dev_id;
+
+ if (data->kernel_panic || hrtimer_active(&data->timer_wde))
+ /* we're either panicking, or already shutting down */
+ return IRQ_HANDLED;
+
+ if (gpiod_get_value(data->gpio_trigger)) {
+ /* button pressed */
+ if (hrtimer_start(&data->timer_trigger, data->trigger_delay,
+ HRTIMER_MODE_REL))
+ dev_err(data->dev, "unable to start the wait timer\n");
+ } else {
+ /* button released */
+ hrtimer_cancel(&data->timer_trigger);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int ltc2952_poweroff_init(struct platform_device *pdev)
+{
+ struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
+
+ data->wde_interval = WDE_TIMEOUT;
+ data->trigger_delay = TRIGGER_TIMEOUT;
+
+ hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
+
+ hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ data->timer_wde.function = ltc2952_poweroff_timer_wde;
+
+ data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(data->gpio_watchdog)) {
+ dev_err(&pdev->dev, "unable to claim watchdog-gpio\n");
+ return PTR_ERR(data->gpio_watchdog);
+ }
+
+ data->gpio_poweroff = devm_gpiod_get(&pdev->dev, "poweroff",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(data->gpio_poweroff)) {
+ dev_err(&pdev->dev, "unable to claim poweroff-gpio\n");
+ return PTR_ERR(data->gpio_poweroff);
+ }
+
+ data->gpio_trigger = devm_gpiod_get(&pdev->dev, "trigger", GPIOD_IN);
+ if (IS_ERR(data->gpio_trigger)) {
+ /*
+ * It's not a problem if the trigger gpio isn't available, but
+ * it is worth a warning its use was defined in the device
+ * tree.
+ */
+ if (PTR_ERR(data->gpio_trigger) != -ENOENT)
+ dev_warn(&pdev->dev, "unable to claim trigger-gpio\n");
+ data->gpio_trigger = NULL;
+ }
+
+ if (devm_request_irq(&pdev->dev,
+ gpiod_to_irq(data->gpio_trigger),
+ ltc2952_poweroff_handler,
+ (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
+ KBUILD_MODNAME, data)) {
+ /*
+ * No trigger input was defined, claiming the gpio failed, we
+ * couldn't map to an irq, or we couldn't register the
+ * interrupt handler. None of these should be a real problem,
+ * but all of them disqualify the push button from controlling
+ * the power.
+ *
+ * It is therefore important to note that if the ltc2952 detects
+ * a button press for long enough, it will still start its own
+ * powerdown window and cut the power on us if we don't start
+ * the watchdog trigger.
+ */
+ if (data->gpio_trigger) {
+ dev_warn(&pdev->dev,
+ "unable to configure the trigger interrupt\n");
+ devm_gpiod_put(&pdev->dev, data->gpio_trigger);
+ data->gpio_trigger = NULL;
+ }
+
+ dev_info(&pdev->dev, "power down trigger input is not used\n");
+ ltc2952_poweroff_start_wde(data);
+ }
+
+ return 0;
+}
+
+static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
+ unsigned long code,
+ void *unused)
+{
+ struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
+
+ data->kernel_panic = true;
+ return NOTIFY_DONE;
+}
+
+/* We need a global pointer here */
+static struct ltc2952_poweroff *ltc2952_data;
+
+static void ltc2952_poweroff_poweroff(void)
+{
+ gpiod_set_value(ltc2952_data->gpio_poweroff, 1);
+}
+
+static int ltc2952_poweroff_probe(struct platform_device *pdev)
+{
+ int ret;
+ struct ltc2952_poweroff *data;
+
+ if (ltc2952_data) {
+ dev_err(&pdev->dev, "already probed");
+ return -ENODEV;
+ }
+
+ if (pm_power_off) {
+ dev_err(&pdev->dev, "pm_power_off already registered");
+ return -EBUSY;
+ }
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->dev = &pdev->dev;
+ platform_set_drvdata(pdev, data);
+
+ ret = ltc2952_poweroff_init(pdev);
+ if (ret)
+ return ret;
+
+ pm_power_off = ltc2952_poweroff_poweroff;
+ ltc2952_data = data;
+
+ data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &data->panic_notifier);
+ dev_info(&pdev->dev, "probe successful\n");
+ return 0;
+}
+
+static int ltc2952_poweroff_remove(struct platform_device *pdev)
+{
+ struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
+
+ pm_power_off = NULL;
+ hrtimer_cancel(&data->timer_wde);
+
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &data->panic_notifier);
+ return 0;
+}
+
+static const struct of_device_id of_ltc2952_poweroff_match[] = {
+ { .compatible = "lltc,ltc2952"},
+ {},
+};
+MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
+
+static struct platform_driver ltc2952_poweroff_driver = {
+ .probe = ltc2952_poweroff_probe,
+ .remove = ltc2952_poweroff_remove,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = of_ltc2952_poweroff_match,
+ },
+};
+module_platform_driver(ltc2952_poweroff_driver);
+
+MODULE_AUTHOR("René Moll <linux@r-moll.nl>");
+MODULE_AUTHOR("Frans Klaver <frans.klaver@xsens.com>");
+MODULE_AUTHOR("Tjerk Hofmeijer <tjerk.hofmeijer@xsens.com>");
+MODULE_DESCRIPTION("LTC PowerPath power-off driver");