/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2019 Intel Corporation
 */

#include <linux/wait_bit.h>

#include <drm/drm_print.h>

#include "intel_runtime_pm.h"
#include "intel_wakeref.h"
#include "i915_drv.h"

int __intel_wakeref_get_first(struct intel_wakeref *wf)
{
        intel_wakeref_t wakeref;
        int ret = 0;

        wakeref = intel_runtime_pm_get(&wf->i915->runtime_pm);
        /*
         * Treat get/put as different subclasses, as we may need to run
         * the put callback from under the shrinker and do not want to
         * cross-contanimate that callback with any extra work performed
         * upon acquiring the wakeref.
         */
        mutex_lock_nested(&wf->mutex, SINGLE_DEPTH_NESTING);

        if (!atomic_read(&wf->count)) {
                INTEL_WAKEREF_BUG_ON(wf->wakeref);
                wf->wakeref = wakeref;
                wakeref = NULL;

                ret = wf->ops->get(wf);
                if (ret) {
                        wakeref = xchg(&wf->wakeref, NULL);
                        wake_up_var(&wf->wakeref);
                        goto unlock;
                }

                smp_mb__before_atomic(); /* release wf->count */
        }

        atomic_inc(&wf->count);
        INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);

unlock:
        mutex_unlock(&wf->mutex);
        if (unlikely(wakeref))
                intel_runtime_pm_put(&wf->i915->runtime_pm, wakeref);

        return ret;
}

static void ____intel_wakeref_put_last(struct intel_wakeref *wf)
{
        intel_wakeref_t wakeref = NULL;

        INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
        if (unlikely(!atomic_dec_and_test(&wf->count)))
                goto unlock;

        /* ops->put() must reschedule its own release on error/deferral */
        if (likely(!wf->ops->put(wf))) {
                INTEL_WAKEREF_BUG_ON(!wf->wakeref);
                wakeref = xchg(&wf->wakeref, NULL);
                wake_up_var(&wf->wakeref);
        }

unlock:
        mutex_unlock(&wf->mutex);
        if (wakeref)
                intel_runtime_pm_put(&wf->i915->runtime_pm, wakeref);
}

void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags)
{
        INTEL_WAKEREF_BUG_ON(delayed_work_pending(&wf->work));

        /* Assume we are not in process context and so cannot sleep. */
        if (flags & INTEL_WAKEREF_PUT_ASYNC || !mutex_trylock(&wf->mutex)) {
                mod_delayed_work(wf->i915->unordered_wq, &wf->work,
                                 FIELD_GET(INTEL_WAKEREF_PUT_DELAY_MASK, flags));
                return;
        }

        ____intel_wakeref_put_last(wf);
}

static void __intel_wakeref_put_work(struct work_struct *wrk)
{
        struct intel_wakeref *wf = container_of(wrk, typeof(*wf), work.work);

        if (atomic_add_unless(&wf->count, -1, 1))
                return;

        mutex_lock(&wf->mutex);
        ____intel_wakeref_put_last(wf);
}

void __intel_wakeref_init(struct intel_wakeref *wf,
                          struct drm_i915_private *i915,
                          const struct intel_wakeref_ops *ops,
                          struct intel_wakeref_lockclass *key,
                          const char *name)
{
        wf->i915 = i915;
        wf->ops = ops;

        __mutex_init(&wf->mutex, "wakeref.mutex", &key->mutex);
        atomic_set(&wf->count, 0);
        wf->wakeref = NULL;

        INIT_DELAYED_WORK(&wf->work, __intel_wakeref_put_work);
        lockdep_init_map(&wf->work.work.lockdep_map,
                         "wakeref.work", &key->work, 0);

#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_WAKEREF)
        if (!wf->debug.class)
                ref_tracker_dir_init(&wf->debug, INTEL_REFTRACK_DEAD_COUNT, "intel_wakeref");
#endif
}

int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
{
        int err;

        might_sleep();

        err = wait_var_event_killable(&wf->wakeref,
                                      !intel_wakeref_is_active(wf));
        if (err)
                return err;

        intel_wakeref_unlock_wait(wf);
        return 0;
}

static void wakeref_auto_timeout(struct timer_list *t)
{
        struct intel_wakeref_auto *wf = timer_container_of(wf, t, timer);
        intel_wakeref_t wakeref;
        unsigned long flags;

        if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
                return;

        wakeref = xchg(&wf->wakeref, NULL);
        spin_unlock_irqrestore(&wf->lock, flags);

        intel_runtime_pm_put(&wf->i915->runtime_pm, wakeref);
}

void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
                             struct drm_i915_private *i915)
{
        spin_lock_init(&wf->lock);
        timer_setup(&wf->timer, wakeref_auto_timeout, 0);
        refcount_set(&wf->count, 0);
        wf->wakeref = NULL;
        wf->i915 = i915;
}

void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
{
        unsigned long flags;

        if (!timeout) {
                if (timer_delete_sync(&wf->timer))
                        wakeref_auto_timeout(&wf->timer);
                return;
        }

        /* Our mission is that we only extend an already active wakeref */
        assert_rpm_wakelock_held(&wf->i915->runtime_pm);

        if (!refcount_inc_not_zero(&wf->count)) {
                spin_lock_irqsave(&wf->lock, flags);
                if (!refcount_inc_not_zero(&wf->count)) {
                        INTEL_WAKEREF_BUG_ON(wf->wakeref);
                        wf->wakeref =
                                intel_runtime_pm_get_if_in_use(&wf->i915->runtime_pm);
                        refcount_set(&wf->count, 1);
                }
                spin_unlock_irqrestore(&wf->lock, flags);
        }

        /*
         * If we extend a pending timer, we will only get a single timer
         * callback and so need to cancel the local inc by running the
         * elided callback to keep the wf->count balanced.
         */
        if (mod_timer(&wf->timer, jiffies + timeout))
                wakeref_auto_timeout(&wf->timer);
}

void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf)
{
        intel_wakeref_auto(wf, 0);
        INTEL_WAKEREF_BUG_ON(wf->wakeref);
}

void intel_ref_tracker_show(struct ref_tracker_dir *dir,
                            struct drm_printer *p)
{
        const size_t buf_size = PAGE_SIZE;
        char *buf, *sb, *se;
        size_t count;

        buf = kmalloc(buf_size, GFP_NOWAIT);
        if (!buf)
                return;

        count = ref_tracker_dir_snprint(dir, buf, buf_size);
        if (!count)
                goto free;
        /* printk does not like big buffers, so we split it */
        for (sb = buf; *sb; sb = se + 1) {
                se = strchrnul(sb, '\n');
                drm_printf(p, "%.*s", (int)(se - sb + 1), sb);
                if (!*se)
                        break;
        }
        if (count >= buf_size)
                drm_printf(p, "\n...dropped %zd extra bytes of leak report.\n",
                           count + 1 - buf_size);
free:
        kfree(buf);
}