/*
 * SVC Greybus "watchdog" driver.
 *
 * Copyright 2016 Google Inc.
 *
 * Released under the GPLv2 only.
 */

#include <linux/delay.h>
#include <linux/suspend.h>
#include <linux/workqueue.h>
#include "greybus.h"

#define SVC_WATCHDOG_PERIOD     (2*HZ)

struct gb_svc_watchdog {
        struct delayed_work     work;
        struct gb_svc           *svc;
        bool                    enabled;
        struct notifier_block pm_notifier;
};

static struct delayed_work reset_work;

static int svc_watchdog_pm_notifier(struct notifier_block *notifier,
                                    unsigned long pm_event, void *unused)
{
        struct gb_svc_watchdog *watchdog =
                container_of(notifier, struct gb_svc_watchdog, pm_notifier);

        switch (pm_event) {
        case PM_SUSPEND_PREPARE:
                gb_svc_watchdog_disable(watchdog->svc);
                break;
        case PM_POST_SUSPEND:
                gb_svc_watchdog_enable(watchdog->svc);
                break;
        default:
                break;
        }

        return NOTIFY_DONE;
}

static void greybus_reset(struct work_struct *work)
{
        static char start_path[256] = "/system/bin/start";
        static char *envp[] = {
                "HOME=/",
                "PATH=/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin",
                NULL,
        };
        static char *argv[] = {
                start_path,
                "unipro_reset",
                NULL,
        };

        printk(KERN_ERR "svc_watchdog: calling \"%s %s\" to reset greybus network!\n",
               argv[0], argv[1]);
        call_usermodehelper(start_path, argv, envp, UMH_WAIT_EXEC);
}

static void do_work(struct work_struct *work)
{
        struct gb_svc_watchdog *watchdog;
        struct gb_svc *svc;
        int retval;

        watchdog = container_of(work, struct gb_svc_watchdog, work.work);
        svc = watchdog->svc;

        dev_dbg(&svc->dev, "%s: ping.\n", __func__);
        retval = gb_svc_ping(svc);
        if (retval) {
                /*
                 * Something went really wrong, let's warn userspace and then
                 * pull the plug and reset the whole greybus network.
                 * We need to do this outside of this workqueue as we will be
                 * tearing down the svc device itself.  So queue up
                 * yet-another-callback to do that.
                 */
                dev_err(&svc->dev,
                        "SVC ping has returned %d, something is wrong!!!\n",
                        retval);

                if (svc->action == GB_SVC_WATCHDOG_BITE_PANIC_KERNEL) {
                        panic("SVC is not responding\n");
                } else if (svc->action == GB_SVC_WATCHDOG_BITE_RESET_UNIPRO) {
                        dev_err(&svc->dev, "Resetting the greybus network, watch out!!!\n");

                        INIT_DELAYED_WORK(&reset_work, greybus_reset);
                        schedule_delayed_work(&reset_work, HZ / 2);

                        /*
                         * Disable ourselves, we don't want to trip again unless
                         * userspace wants us to.
                         */
                        watchdog->enabled = false;
                }
        }

        /* resubmit our work to happen again, if we are still "alive" */
        if (watchdog->enabled)
                schedule_delayed_work(&watchdog->work, SVC_WATCHDOG_PERIOD);
}

int gb_svc_watchdog_create(struct gb_svc *svc)
{
        struct gb_svc_watchdog *watchdog;
        int retval;

        if (svc->watchdog)
                return 0;

        watchdog = kmalloc(sizeof(*watchdog), GFP_KERNEL);
        if (!watchdog)
                return -ENOMEM;

        watchdog->enabled = false;
        watchdog->svc = svc;
        INIT_DELAYED_WORK(&watchdog->work, do_work);
        svc->watchdog = watchdog;

        watchdog->pm_notifier.notifier_call = svc_watchdog_pm_notifier;
        retval = register_pm_notifier(&watchdog->pm_notifier);
        if (retval) {
                dev_err(&svc->dev, "error registering pm notifier(%d)\n",
                        retval);
                goto svc_watchdog_create_err;
        }

        retval = gb_svc_watchdog_enable(svc);
        if (retval) {
                dev_err(&svc->dev, "error enabling watchdog (%d)\n", retval);
                unregister_pm_notifier(&watchdog->pm_notifier);
                goto svc_watchdog_create_err;
        }
        return retval;

svc_watchdog_create_err:
        svc->watchdog = NULL;
        kfree(watchdog);

        return retval;
}

void gb_svc_watchdog_destroy(struct gb_svc *svc)
{
        struct gb_svc_watchdog *watchdog = svc->watchdog;

        if (!watchdog)
                return;

        unregister_pm_notifier(&watchdog->pm_notifier);
        gb_svc_watchdog_disable(svc);
        svc->watchdog = NULL;
        kfree(watchdog);
}

bool gb_svc_watchdog_enabled(struct gb_svc *svc)
{
        if (!svc || !svc->watchdog)
                return false;
        return svc->watchdog->enabled;
}

int gb_svc_watchdog_enable(struct gb_svc *svc)
{
        struct gb_svc_watchdog *watchdog;

        if (!svc->watchdog)
                return -ENODEV;

        watchdog = svc->watchdog;
        if (watchdog->enabled)
                return 0;

        watchdog->enabled = true;
        schedule_delayed_work(&watchdog->work, SVC_WATCHDOG_PERIOD);
        return 0;
}

int gb_svc_watchdog_disable(struct gb_svc *svc)
{
        struct gb_svc_watchdog *watchdog;

        if (!svc->watchdog)
                return -ENODEV;

        watchdog = svc->watchdog;
        if (!watchdog->enabled)
                return 0;

        watchdog->enabled = false;
        cancel_delayed_work_sync(&watchdog->work);
        return 0;
}