power: reset: add LTC2952 poweroff driver
This adds a driver for the LTC2952, an external power control chip,
which signals the OS to shut down. Additionally this driver lets the
kernel power down the board.
Signed-off-by: René Moll <rene.moll@xsens.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
diff --git a/drivers/power/reset/ltc2952-poweroff.c b/drivers/power/reset/ltc2952-poweroff.c
new file mode 100644
index 0000000..116a1ce
--- /dev/null
+++ b/drivers/power/reset/ltc2952-poweroff.c
@@ -0,0 +1,386 @@
+/*
+ * LTC2952 (PowerPath) driver
+ *
+ * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com>
+ * Maintainer: René Moll <linux@r-moll.nl>
+ *
+ * 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 PowerPath Controller (LTC2952).
+ * Its function is to determine when a external shut down 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)
+ * A level change indicates the shut-down trigger. If it's state reverts
+ * within the time-out defined by trigger_delay, the shut down is not
+ * executed.
+ *
+ * - watchdog (output)
+ * Once a shut down is triggered, the driver will toggle this signal,
+ * with an internal (wde_interval) to stall the hardware shut down.
+ *
+ * - kill (output)
+ * The last action during shut down 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>
+
+struct ltc2952_poweroff_data {
+ struct hrtimer timer_trigger;
+ struct hrtimer timer_wde;
+
+ ktime_t trigger_delay;
+ ktime_t wde_interval;
+
+ struct device *dev;
+
+ unsigned int virq;
+
+ /**
+ * 0: trigger
+ * 1: watchdog
+ * 2: kill
+ */
+ struct gpio_desc *gpio[3];
+};
+
+static int ltc2952_poweroff_panic;
+static struct ltc2952_poweroff_data *ltc2952_data;
+
+#define POWERPATH_IO_TRIGGER 0
+#define POWERPATH_IO_WATCHDOG 1
+#define POWERPATH_IO_KILL 2
+
+/**
+ * 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;
+ unsigned long overruns;
+
+ if (ltc2952_poweroff_panic)
+ return HRTIMER_NORESTART;
+
+ state = gpiod_get_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG]);
+ gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], !state);
+
+ now = hrtimer_cb_get_time(timer);
+ overruns = hrtimer_forward(timer, now, ltc2952_data->wde_interval);
+
+ return HRTIMER_RESTART;
+}
+
+static enum hrtimer_restart ltc2952_poweroff_timer_trigger(
+ struct hrtimer *timer)
+{
+ int ret;
+
+ ret = hrtimer_start(<c2952_data->timer_wde,
+ ltc2952_data->wde_interval, HRTIMER_MODE_REL);
+
+ if (ret) {
+ dev_err(ltc2952_data->dev, "unable to start the timer\n");
+ /*
+ * 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 sending a warning as the system will power-off anyway
+ */
+ }
+
+ dev_info(ltc2952_data->dev, "executing shutdown\n");
+
+ orderly_poweroff(true);
+
+ return HRTIMER_NORESTART;
+}
+
+/**
+ * ltc2952_poweroff_handler - Interrupt handler
+ * Triggered each time the trigger signal changes state and (de)activates a
+ * time-out (timer_trigger). Once the time-out is actually reached the shut
+ * down is executed.
+ *
+ * @irq: IRQ number
+ * @dev_id: pointer to the main data structure
+ */
+static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
+{
+ int ret;
+ struct ltc2952_poweroff_data *data = dev_id;
+
+ if (ltc2952_poweroff_panic)
+ goto irq_ok;
+
+ if (hrtimer_active(&data->timer_wde)) {
+ /* shutdown is already triggered, nothing to do any more */
+ goto irq_ok;
+ }
+
+ if (!hrtimer_active(&data->timer_trigger)) {
+ ret = hrtimer_start(&data->timer_trigger, data->trigger_delay,
+ HRTIMER_MODE_REL);
+
+ if (ret)
+ dev_err(data->dev, "unable to start the wait timer\n");
+ } else {
+ ret = hrtimer_cancel(&data->timer_trigger);
+ /* omitting return value check, timer should have been valid */
+ }
+
+irq_ok:
+ return IRQ_HANDLED;
+}
+
+static void ltc2952_poweroff_kill(void)
+{
+ gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_KILL], 1);
+}
+
+static int ltc2952_poweroff_suspend(struct platform_device *pdev,
+ pm_message_t state)
+{
+ return -ENOSYS;
+}
+
+static int ltc2952_poweroff_resume(struct platform_device *pdev)
+{
+ return -ENOSYS;
+}
+
+static void ltc2952_poweroff_default(struct ltc2952_poweroff_data *data)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(data->gpio); i++)
+ data->gpio[i] = NULL;
+
+ data->wde_interval = ktime_set(0, 300L*1E6L);
+ data->trigger_delay = ktime_set(2, 500L*1E6L);
+
+ hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ data->timer_trigger.function = <c2952_poweroff_timer_trigger;
+
+ hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ data->timer_wde.function = <c2952_poweroff_timer_wde;
+}
+
+static int ltc2952_poweroff_init(struct platform_device *pdev)
+{
+ int ret, virq;
+ unsigned int i;
+ struct ltc2952_poweroff_data *data;
+
+ static char *name[] = {
+ "trigger",
+ "watchdog",
+ "kill",
+ NULL
+ };
+
+ data = ltc2952_data;
+ ltc2952_poweroff_default(ltc2952_data);
+
+ for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++) {
+ ltc2952_data->gpio[i] = gpiod_get(&pdev->dev, name[i]);
+
+ if (IS_ERR(ltc2952_data->gpio[i])) {
+ ret = PTR_ERR(ltc2952_data->gpio[i]);
+ dev_err(&pdev->dev,
+ "unable to claim the following gpio: %s\n",
+ name[i]);
+ goto err_io;
+ }
+ }
+
+ ret = gpiod_direction_output(
+ ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], 0);
+ if (ret) {
+ dev_err(&pdev->dev, "unable to use watchdog-gpio as output\n");
+ goto err_io;
+ }
+
+ ret = gpiod_direction_output(ltc2952_data->gpio[POWERPATH_IO_KILL], 0);
+ if (ret) {
+ dev_err(&pdev->dev, "unable to use kill-gpio as output\n");
+ goto err_io;
+ }
+
+ virq = gpiod_to_irq(ltc2952_data->gpio[POWERPATH_IO_TRIGGER]);
+ if (virq < 0) {
+ dev_err(&pdev->dev, "cannot map GPIO as interrupt");
+ goto err_io;
+ }
+
+ ltc2952_data->virq = virq;
+ ret = request_irq(virq,
+ ltc2952_poweroff_handler,
+ (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
+ "ltc2952-poweroff",
+ ltc2952_data
+ );
+
+ if (ret) {
+ dev_err(&pdev->dev, "cannot configure an interrupt handler\n");
+ goto err_io;
+ }
+
+ return 0;
+
+err_io:
+ for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
+ if (ltc2952_data->gpio[i])
+ gpiod_put(ltc2952_data->gpio[i]);
+
+ return ret;
+}
+
+static int ltc2952_poweroff_probe(struct platform_device *pdev)
+{
+ int ret;
+
+ if (pm_power_off) {
+ dev_err(&pdev->dev, "pm_power_off already registered");
+ return -EBUSY;
+ }
+
+ ltc2952_data = kzalloc(sizeof(*ltc2952_data), GFP_KERNEL);
+ if (!ltc2952_data)
+ return -ENOMEM;
+
+ ltc2952_data->dev = &pdev->dev;
+
+ ret = ltc2952_poweroff_init(pdev);
+ if (ret)
+ goto err;
+
+ pm_power_off = <c2952_poweroff_kill;
+
+ dev_info(&pdev->dev, "probe successful\n");
+
+ return 0;
+
+err:
+ kfree(ltc2952_data);
+ return ret;
+}
+
+static int ltc2952_poweroff_remove(struct platform_device *pdev)
+{
+ unsigned int i;
+
+ pm_power_off = NULL;
+
+ if (ltc2952_data) {
+ free_irq(ltc2952_data->virq, ltc2952_data);
+
+ for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
+ gpiod_put(ltc2952_data->gpio[i]);
+
+ kfree(ltc2952_data);
+ }
+
+ 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 = "ltc2952-poweroff",
+ .owner = THIS_MODULE,
+ .of_match_table = of_ltc2952_poweroff_match,
+ },
+ .suspend = ltc2952_poweroff_suspend,
+ .resume = ltc2952_poweroff_resume,
+};
+
+static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
+ unsigned long code, void *unused)
+{
+ ltc2952_poweroff_panic = 1;
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block ltc2952_poweroff_panic_nb = {
+ .notifier_call = ltc2952_poweroff_notify_panic,
+};
+
+static int __init ltc2952_poweroff_platform_init(void)
+{
+ ltc2952_poweroff_panic = 0;
+
+ atomic_notifier_chain_register(&panic_notifier_list,
+ <c2952_poweroff_panic_nb);
+
+ return platform_driver_register(<c2952_poweroff_driver);
+}
+
+static void __exit ltc2952_poweroff_platform_exit(void)
+{
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ <c2952_poweroff_panic_nb);
+
+ platform_driver_unregister(<c2952_poweroff_driver);
+}
+
+module_init(ltc2952_poweroff_platform_init);
+module_exit(ltc2952_poweroff_platform_exit);
+
+MODULE_AUTHOR("René Moll <rene.moll@xsens.com>");
+MODULE_DESCRIPTION("LTC PowerPath power-off driver");
+MODULE_LICENSE("GPL v2");