drivers/gpu/drm/i915/intel_wakeref.c

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2019 Intel Corporation
   5  */
   6
   7 #include <linux/wait_bit.h>
   8
   9 #include "intel_runtime_pm.h"
  10 #include "intel_wakeref.h"
  11
  12 static void rpm_get(struct intel_wakeref *wf)
  13 {
  14         wf->wakeref = intel_runtime_pm_get(wf->rpm);
  15 }
  16
  17 static void rpm_put(struct intel_wakeref *wf)
  18 {
  19         intel_wakeref_t wakeref = fetch_and_zero(&wf->wakeref);
  20
  21         intel_runtime_pm_put(wf->rpm, wakeref);
  22         INTEL_WAKEREF_BUG_ON(!wakeref);
  23 }
  24
  25 int __intel_wakeref_get_first(struct intel_wakeref *wf)
  26 {
  27         /*
  28          * Treat get/put as different subclasses, as we may need to run
  29          * the put callback from under the shrinker and do not want to
  30          * cross-contanimate that callback with any extra work performed
  31          * upon acquiring the wakeref.
  32          */
  33         mutex_lock_nested(&wf->mutex, SINGLE_DEPTH_NESTING);
  34         if (!atomic_read(&wf->count)) {
  35                 int err;
  36
  37                 rpm_get(wf);
  38
  39                 err = wf->ops->get(wf);
  40                 if (unlikely(err)) {
  41                         rpm_put(wf);
  42                         mutex_unlock(&wf->mutex);
  43                         return err;
  44                 }
  45
  46                 smp_mb__before_atomic(); /* release wf->count */
  47         }
  48         atomic_inc(&wf->count);
  49         mutex_unlock(&wf->mutex);
  50
  51         INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
  52         return 0;
  53 }
  54
  55 static void ____intel_wakeref_put_last(struct intel_wakeref *wf)
  56 {
  57         if (!atomic_dec_and_test(&wf->count))
  58                 goto unlock;
  59
  60         if (likely(!wf->ops->put(wf))) {
  61                 rpm_put(wf);
  62                 wake_up_var(&wf->wakeref);
  63         } else {
  64                 /* ops->put() must schedule its own release on deferral */
  65                 atomic_set_release(&wf->count, 1);
  66         }
  67
  68 unlock:
  69         mutex_unlock(&wf->mutex);
  70 }
  71
  72 void __intel_wakeref_put_last(struct intel_wakeref *wf)
  73 {
  74         INTEL_WAKEREF_BUG_ON(work_pending(&wf->work));
  75
  76         /* Assume we are not in process context and so cannot sleep. */
  77         if (wf->ops->flags & INTEL_WAKEREF_PUT_ASYNC ||
  78             !mutex_trylock(&wf->mutex)) {
  79                 schedule_work(&wf->work);
  80                 return;
  81         }
  82
  83         ____intel_wakeref_put_last(wf);
  84 }
  85
  86 static void __intel_wakeref_put_work(struct work_struct *wrk)
  87 {
  88         struct intel_wakeref *wf = container_of(wrk, typeof(*wf), work);
  89
  90         if (atomic_add_unless(&wf->count, -1, 1))
  91                 return;
  92
  93         mutex_lock(&wf->mutex);
  94         ____intel_wakeref_put_last(wf);
  95 }
  96
  97 void __intel_wakeref_init(struct intel_wakeref *wf,
  98                           struct intel_runtime_pm *rpm,
  99                           const struct intel_wakeref_ops *ops,
 100                           struct lock_class_key *key)
 101 {
 102         wf->rpm = rpm;
 103         wf->ops = ops;
 104
 105         __mutex_init(&wf->mutex, "wakeref", key);
 106         atomic_set(&wf->count, 0);
 107         wf->wakeref = 0;
 108
 109         INIT_WORK(&wf->work, __intel_wakeref_put_work);
 110 }
 111
 112 int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
 113 {
 114         return wait_var_event_killable(&wf->wakeref,
 115                                        !intel_wakeref_is_active(wf));
 116 }
 117
 118 static void wakeref_auto_timeout(struct timer_list *t)
 119 {
 120         struct intel_wakeref_auto *wf = from_timer(wf, t, timer);
 121         intel_wakeref_t wakeref;
 122         unsigned long flags;
 123
 124         if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
 125                 return;
 126
 127         wakeref = fetch_and_zero(&wf->wakeref);
 128         spin_unlock_irqrestore(&wf->lock, flags);
 129
 130         intel_runtime_pm_put(wf->rpm, wakeref);
 131 }
 132
 133 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
 134                              struct intel_runtime_pm *rpm)
 135 {
 136         spin_lock_init(&wf->lock);
 137         timer_setup(&wf->timer, wakeref_auto_timeout, 0);
 138         refcount_set(&wf->count, 0);
 139         wf->wakeref = 0;
 140         wf->rpm = rpm;
 141 }
 142
 143 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
 144 {
 145         unsigned long flags;
 146
 147         if (!timeout) {
 148                 if (del_timer_sync(&wf->timer))
 149                         wakeref_auto_timeout(&wf->timer);
 150                 return;
 151         }
 152
 153         /* Our mission is that we only extend an already active wakeref */
 154         assert_rpm_wakelock_held(wf->rpm);
 155
 156         if (!refcount_inc_not_zero(&wf->count)) {
 157                 spin_lock_irqsave(&wf->lock, flags);
 158                 if (!refcount_inc_not_zero(&wf->count)) {
 159                         INTEL_WAKEREF_BUG_ON(wf->wakeref);
 160                         wf->wakeref = intel_runtime_pm_get_if_in_use(wf->rpm);
 161                         refcount_set(&wf->count, 1);
 162                 }
 163                 spin_unlock_irqrestore(&wf->lock, flags);
 164         }
 165
 166         /*
 167          * If we extend a pending timer, we will only get a single timer
 168          * callback and so need to cancel the local inc by running the
 169          * elided callback to keep the wf->count balanced.
 170          */
 171         if (mod_timer(&wf->timer, jiffies + timeout))
 172                 wakeref_auto_timeout(&wf->timer);
 173 }
 174
 175 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf)
 176 {
 177         intel_wakeref_auto(wf, 0);
 178         INTEL_WAKEREF_BUG_ON(wf->wakeref);
 179 }