/*
 * 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.
 *
 * 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.
 *
 * Copyright (C) 2016 ARM Limited
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/cpu_pm.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <uapi/linux/sched/types.h>
#include <linux/module.h>
#include <linux/preempt.h>
#include <linux/psci.h>
#include <linux/slab.h>
#include <linux/tick.h>
#include <linux/topology.h>

#include <asm/cpuidle.h>

#include <uapi/linux/psci.h>

#define NUM_SUSPEND_CYCLE (10)

static unsigned int nb_available_cpus;
static int tos_resident_cpu = -1;

static atomic_t nb_active_threads;
static struct completion suspend_threads_started =
        COMPLETION_INITIALIZER(suspend_threads_started);
static struct completion suspend_threads_done =
        COMPLETION_INITIALIZER(suspend_threads_done);

/*
 * We assume that PSCI operations are used if they are available. This is not
 * necessarily true on arm64, since the decision is based on the
 * "enable-method" property of each CPU in the DT, but given that there is no
 * arch-specific way to check this, we assume that the DT is sensible.
 */
static int psci_ops_check(void)
{
        int migrate_type = -1;
        int cpu;

        if (!(psci_ops.cpu_off && psci_ops.cpu_on && psci_ops.cpu_suspend)) {
                pr_warn("Missing PSCI operations, aborting tests\n");
                return -EOPNOTSUPP;
        }

        if (psci_ops.migrate_info_type)
                migrate_type = psci_ops.migrate_info_type();

        if (migrate_type == PSCI_0_2_TOS_UP_MIGRATE ||
            migrate_type == PSCI_0_2_TOS_UP_NO_MIGRATE) {
                /* There is a UP Trusted OS, find on which core it resides. */
                for_each_online_cpu(cpu)
                        if (psci_tos_resident_on(cpu)) {
                                tos_resident_cpu = cpu;
                                break;
                        }
                if (tos_resident_cpu == -1)
                        pr_warn("UP Trusted OS resides on no online CPU\n");
        }

        return 0;
}

static int find_cpu_groups(const struct cpumask *cpus,
                           const struct cpumask **cpu_groups)
{
        unsigned int nb = 0;
        cpumask_var_t tmp;

        if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
                return -ENOMEM;
        cpumask_copy(tmp, cpus);

        while (!cpumask_empty(tmp)) {
                const struct cpumask *cpu_group =
                        topology_core_cpumask(cpumask_any(tmp));

                cpu_groups[nb++] = cpu_group;
                cpumask_andnot(tmp, tmp, cpu_group);
        }

        free_cpumask_var(tmp);
        return nb;
}

/*
 * offlined_cpus is a temporary array but passing it as an argument avoids
 * multiple allocations.
 */
static unsigned int down_and_up_cpus(const struct cpumask *cpus,
                                     struct cpumask *offlined_cpus)
{
        int cpu;
        int err = 0;

        cpumask_clear(offlined_cpus);

        /* Try to power down all CPUs in the mask. */
        for_each_cpu(cpu, cpus) {
                int ret = cpu_down(cpu);

                /*
                 * cpu_down() checks the number of online CPUs before the TOS
                 * resident CPU.
                 */
                if (cpumask_weight(offlined_cpus) + 1 == nb_available_cpus) {
                        if (ret != -EBUSY) {
                                pr_err("Unexpected return code %d while trying "
                                       "to power down last online CPU %d\n",
                                       ret, cpu);
                                ++err;
                        }
                } else if (cpu == tos_resident_cpu) {
                        if (ret != -EPERM) {
                                pr_err("Unexpected return code %d while trying "
                                       "to power down TOS resident CPU %d\n",
                                       ret, cpu);
                                ++err;
                        }
                } else if (ret != 0) {
                        pr_err("Error occurred (%d) while trying "
                               "to power down CPU %d\n", ret, cpu);
                        ++err;
                }

                if (ret == 0)
                        cpumask_set_cpu(cpu, offlined_cpus);
        }

        /* Try to power up all the CPUs that have been offlined. */
        for_each_cpu(cpu, offlined_cpus) {
                int ret = cpu_up(cpu);

                if (ret != 0) {
                        pr_err("Error occurred (%d) while trying "
                               "to power up CPU %d\n", ret, cpu);
                        ++err;
                } else {
                        cpumask_clear_cpu(cpu, offlined_cpus);
                }
        }

        /*
         * Something went bad at some point and some CPUs could not be turned
         * back on.
         */
        WARN_ON(!cpumask_empty(offlined_cpus) ||
                num_online_cpus() != nb_available_cpus);

        return err;
}

static int hotplug_tests(void)
{
        int err;
        cpumask_var_t offlined_cpus;
        int i, nb_cpu_group;
        const struct cpumask **cpu_groups;
        char *page_buf;

        err = -ENOMEM;
        if (!alloc_cpumask_var(&offlined_cpus, GFP_KERNEL))
                return err;
        /* We may have up to nb_available_cpus cpu_groups. */
        cpu_groups = kmalloc_array(nb_available_cpus, sizeof(*cpu_groups),
                                   GFP_KERNEL);
        if (!cpu_groups)
                goto out_free_cpus;
        page_buf = (char *)__get_free_page(GFP_KERNEL);
        if (!page_buf)
                goto out_free_cpu_groups;

        err = 0;
        nb_cpu_group = find_cpu_groups(cpu_online_mask, cpu_groups);

        /*
         * Of course the last CPU cannot be powered down and cpu_down() should
         * refuse doing that.
         */
        pr_info("Trying to turn off and on again all CPUs\n");
        err += down_and_up_cpus(cpu_online_mask, offlined_cpus);

        /*
         * Take down CPUs by cpu group this time. When the last CPU is turned
         * off, the cpu group itself should shut down.
         */
        for (i = 0; i < nb_cpu_group; ++i) {
                ssize_t len = cpumap_print_to_pagebuf(true, page_buf,
                                                      cpu_groups[i]);
                /* Remove trailing newline. */
                page_buf[len - 1] = '\0';
                pr_info("Trying to turn off and on again group %d (CPUs %s)\n",
                        i, page_buf);
                err += down_and_up_cpus(cpu_groups[i], offlined_cpus);
        }

        free_page((unsigned long)page_buf);
out_free_cpu_groups:
        kfree(cpu_groups);
out_free_cpus:
        free_cpumask_var(offlined_cpus);
        return err;
}

static void dummy_callback(struct timer_list *unused) {}

static int suspend_cpu(int index, bool broadcast)
{
        int ret;

        arch_cpu_idle_enter();

        if (broadcast) {
                /*
                 * The local timer will be shut down, we need to enter tick
                 * broadcast.
                 */
                ret = tick_broadcast_enter();
                if (ret) {
                        /*
                         * In the absence of hardware broadcast mechanism,
                         * this CPU might be used to broadcast wakeups, which
                         * may be why entering tick broadcast has failed.
                         * There is little the kernel can do to work around
                         * that, so enter WFI instead (idle state 0).
                         */
                        cpu_do_idle();
                        ret = 0;
                        goto out_arch_exit;
                }
        }

        /*
         * Replicate the common ARM cpuidle enter function
         * (arm_enter_idle_state).
         */
        ret = CPU_PM_CPU_IDLE_ENTER(arm_cpuidle_suspend, index);

        if (broadcast)
                tick_broadcast_exit();

out_arch_exit:
        arch_cpu_idle_exit();

        return ret;
}

static int suspend_test_thread(void *arg)
{
        int cpu = (long)arg;
        int i, nb_suspend = 0, nb_shallow_sleep = 0, nb_err = 0;
        struct sched_param sched_priority = { .sched_priority = MAX_RT_PRIO-1 };
        struct cpuidle_device *dev;
        struct cpuidle_driver *drv;
        /* No need for an actual callback, we just want to wake up the CPU. */
        struct timer_list wakeup_timer;

        /* Wait for the main thread to give the start signal. */
        wait_for_completion(&suspend_threads_started);

        /* Set maximum priority to preempt all other threads on this CPU. */
        if (sched_setscheduler_nocheck(current, SCHED_FIFO, &sched_priority))
                pr_warn("Failed to set suspend thread scheduler on CPU %d\n",
                        cpu);

        dev = this_cpu_read(cpuidle_devices);
        drv = cpuidle_get_cpu_driver(dev);

        pr_info("CPU %d entering suspend cycles, states 1 through %d\n",
                cpu, drv->state_count - 1);

        timer_setup_on_stack(&wakeup_timer, dummy_callback, 0);
        for (i = 0; i < NUM_SUSPEND_CYCLE; ++i) {
                int index;
                /*
                 * Test all possible states, except 0 (which is usually WFI and
                 * doesn't use PSCI).
                 */
                for (index = 1; index < drv->state_count; ++index) {
                        struct cpuidle_state *state = &drv->states[index];
                        bool broadcast = state->flags & CPUIDLE_FLAG_TIMER_STOP;
                        int ret;

                        /*
                         * Set the timer to wake this CPU up in some time (which
                         * should be largely sufficient for entering suspend).
                         * If the local tick is disabled when entering suspend,
                         * suspend_cpu() takes care of switching to a broadcast
                         * tick, so the timer will still wake us up.
                         */
                        mod_timer(&wakeup_timer, jiffies +
                                  usecs_to_jiffies(state->target_residency));

                        /* IRQs must be disabled during suspend operations. */
                        local_irq_disable();

                        ret = suspend_cpu(index, broadcast);

                        /*
                         * We have woken up. Re-enable IRQs to handle any
                         * pending interrupt, do not wait until the end of the
                         * loop.
                         */
                        local_irq_enable();

                        if (ret == index) {
                                ++nb_suspend;
                        } else if (ret >= 0) {
                                /* We did not enter the expected state. */
                                ++nb_shallow_sleep;
                        } else {
                                pr_err("Failed to suspend CPU %d: error %d "
                                       "(requested state %d, cycle %d)\n",
                                       cpu, ret, index, i);
                                ++nb_err;
                        }
                }
        }

        /*
         * Disable the timer to make sure that the timer will not trigger
         * later.
         */
        del_timer(&wakeup_timer);
        destroy_timer_on_stack(&wakeup_timer);

        if (atomic_dec_return_relaxed(&nb_active_threads) == 0)
                complete(&suspend_threads_done);

        /* Give up on RT scheduling and wait for termination. */
        sched_priority.sched_priority = 0;
        if (sched_setscheduler_nocheck(current, SCHED_NORMAL, &sched_priority))
                pr_warn("Failed to set suspend thread scheduler on CPU %d\n",
                        cpu);
        for (;;) {
                /* Needs to be set first to avoid missing a wakeup. */
                set_current_state(TASK_INTERRUPTIBLE);
                if (kthread_should_stop()) {
                        __set_current_state(TASK_RUNNING);
                        break;
                }
                schedule();
        }

        pr_info("CPU %d suspend test results: success %d, shallow states %d, errors %d\n",
                cpu, nb_suspend, nb_shallow_sleep, nb_err);

        return nb_err;
}

static int suspend_tests(void)
{
        int i, cpu, err = 0;
        struct task_struct **threads;
        int nb_threads = 0;

        threads = kmalloc_array(nb_available_cpus, sizeof(*threads),
                                GFP_KERNEL);
        if (!threads)
                return -ENOMEM;

        /*
         * Stop cpuidle to prevent the idle tasks from entering a deep sleep
         * mode, as it might interfere with the suspend threads on other CPUs.
         * This does not prevent the suspend threads from using cpuidle (only
         * the idle tasks check this status). Take the idle lock so that
         * the cpuidle driver and device look-up can be carried out safely.
         */
        cpuidle_pause_and_lock();

        for_each_online_cpu(cpu) {
                struct task_struct *thread;
                /* Check that cpuidle is available on that CPU. */
                struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
                struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

                if (!dev || !drv) {
                        pr_warn("cpuidle not available on CPU %d, ignoring\n",
                                cpu);
                        continue;
                }

                thread = kthread_create_on_cpu(suspend_test_thread,
                                               (void *)(long)cpu, cpu,
                                               "psci_suspend_test");
                if (IS_ERR(thread))
                        pr_err("Failed to create kthread on CPU %d\n", cpu);
                else
                        threads[nb_threads++] = thread;
        }

        if (nb_threads < 1) {
                err = -ENODEV;
                goto out;
        }

        atomic_set(&nb_active_threads, nb_threads);

        /*
         * Wake up the suspend threads. To avoid the main thread being preempted
         * before all the threads have been unparked, the suspend threads will
         * wait for the completion of suspend_threads_started.
         */
        for (i = 0; i < nb_threads; ++i)
                wake_up_process(threads[i]);
        complete_all(&suspend_threads_started);

        wait_for_completion(&suspend_threads_done);


        /* Stop and destroy all threads, get return status. */
        for (i = 0; i < nb_threads; ++i)
                err += kthread_stop(threads[i]);
 out:
        cpuidle_resume_and_unlock();
        kfree(threads);
        return err;
}

static int __init psci_checker(void)
{
        int ret;

        /*
         * Since we're in an initcall, we assume that all the CPUs that all
         * CPUs that can be onlined have been onlined.
         *
         * The tests assume that hotplug is enabled but nobody else is using it,
         * otherwise the results will be unpredictable. However, since there
         * is no userspace yet in initcalls, that should be fine, as long as
         * no torture test is running at the same time (see Kconfig).
         */
        nb_available_cpus = num_online_cpus();

        /* Check PSCI operations are set up and working. */
        ret = psci_ops_check();
        if (ret)
                return ret;

        pr_info("PSCI checker started using %u CPUs\n", nb_available_cpus);

        pr_info("Starting hotplug tests\n");
        ret = hotplug_tests();
        if (ret == 0)
                pr_info("Hotplug tests passed OK\n");
        else if (ret > 0)
                pr_err("%d error(s) encountered in hotplug tests\n", ret);
        else {
                pr_err("Out of memory\n");
                return ret;
        }

        pr_info("Starting suspend tests (%d cycles per state)\n",
                NUM_SUSPEND_CYCLE);
        ret = suspend_tests();
        if (ret == 0)
                pr_info("Suspend tests passed OK\n");
        else if (ret > 0)
                pr_err("%d error(s) encountered in suspend tests\n", ret);
        else {
                switch (ret) {
                case -ENOMEM:
                        pr_err("Out of memory\n");
                        break;
                case -ENODEV:
                        pr_warn("Could not start suspend tests on any CPU\n");
                        break;
                }
        }

        pr_info("PSCI checker completed\n");
        return ret < 0 ? ret : 0;
}
late_initcall(psci_checker);