drm/i915: Keep user GGTT alive for a minimum of 250ms

Do not allow runtime pm autosuspend to remove userspace GGTT mmaps too
quickly. For example, igt sets the autosuspend delay to 0, and so we
immediately attempt to perform runtime suspend upon releasing the
wakeref. Unfortunately, that involves tearing down GGTT mmaps as they
require an active device.

Override the autosuspend for GGTT mmaps, by keeping the wakeref around
for 250ms after populating the PTE for a fresh mmap.

v2: Prefer refcount_t for its under/overflow error detection
v3: Flush the user runtime autosuspend prior to system system.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190527115114.13448-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
index 0e5db98da8f3a952b14d5e1b8d0cb14185a607bd..4fd1ea639d0f74d28e8354cda267e63e532b8778 100644 (file)
--- a/drivers/gpu/drm/i915/Kconfig.profile
+++ b/drivers/gpu/drm/i915/Kconfig.profile
@@ -1,3 +1,17 @@
+config DRM_I915_USERFAULT_AUTOSUSPEND
+       int "Runtime autosuspend delay for userspace GGTT mmaps (ms)"
+       default 250 # milliseconds
+       help
+         On runtime suspend, as we suspend the device, we have to revoke
+         userspace GGTT mmaps and force userspace to take a pagefault on
+         their next access. The revocation and subsequent recreation of
+         the GGTT mmap can be very slow and so we impose a small hysteris
+         that complements the runtime-pm autosuspend and provides a lower
+         floor on the autosuspend delay.
+
+         May be 0 to disable the extra delay and solely use the device level
+         runtime pm autosuspend delay tunable.
+
 config DRM_I915_SPIN_REQUEST
        int
        default 5 # microseconds

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 764347e7cf2d53fa69e451ac752041e894c81fa1..87cc80c7b6269e244c3eb92597a6f7b8394e419f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -875,6 +875,9 @@ struct i915_gem_mm {
         */
        struct list_head userfault_list;
 
+       /* Manual runtime pm autosuspend delay for user GGTT mmaps */
+       struct intel_wakeref_auto userfault_wakeref;
+
        /**
         * List of objects which are pending destruction.
         */

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7cafd5612f71471a29944d4a55ceeb979de984fc..50f72ae39ad897d81cef13bb87bbec618def48ca 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1834,6 +1834,9 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
        assert_rpm_wakelock_held(dev_priv);
        if (!i915_vma_set_userfault(vma) && !obj->userfault_count++)
                list_add(&obj->userfault_link, &dev_priv->mm.userfault_list);
+       if (CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
+               intel_wakeref_auto(&dev_priv->mm.userfault_wakeref,
+                                  msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));
        GEM_BUG_ON(!obj->userfault_count);
 
        i915_vma_set_ggtt_write(vma);
@@ -4671,6 +4674,8 @@ void i915_gem_fini(struct drm_i915_private *dev_priv)
 {
        GEM_BUG_ON(dev_priv->gt.awake);
 
+       intel_wakeref_auto_fini(&dev_priv->mm.userfault_wakeref);
+
        i915_gem_suspend_late(dev_priv);
        intel_disable_gt_powersave(dev_priv);
 
@@ -4746,7 +4751,9 @@ static void i915_gem_init__mm(struct drm_i915_private *i915)
        INIT_LIST_HEAD(&i915->mm.unbound_list);
        INIT_LIST_HEAD(&i915->mm.bound_list);
        INIT_LIST_HEAD(&i915->mm.fence_list);
+
        INIT_LIST_HEAD(&i915->mm.userfault_list);
+       intel_wakeref_auto_init(&i915->mm.userfault_wakeref, i915);
 
        INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
 }

diff --git a/drivers/gpu/drm/i915/i915_gem_pm.c b/drivers/gpu/drm/i915/i915_gem_pm.c
index fa9c2ebd966ab84415161a322125b29121d70a10..c0ad196052972e56a9f4ea050734607e9efa247f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_pm.c
+++ b/drivers/gpu/drm/i915/i915_gem_pm.c
@@ -126,6 +126,7 @@ void i915_gem_suspend(struct drm_i915_private *i915)
 {
        GEM_TRACE("\n");
 
+       intel_wakeref_auto(&i915->mm.userfault_wakeref, 0);
        flush_workqueue(i915->wq);
 
        mutex_lock(&i915->drm.struct_mutex);

diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
index 91196d9612bbf2f4a8d089b94c03d384b1d75341..c2dda5a375f09ba6a5371970d15e76daf4feae40 100644 (file)
--- a/drivers/gpu/drm/i915/intel_wakeref.c
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -73,3 +73,66 @@ void __intel_wakeref_init(struct intel_wakeref *wf, struct lock_class_key *key)
        atomic_set(&wf->count, 0);
        wf->wakeref = 0;
 }
+
+static void wakeref_auto_timeout(struct timer_list *t)
+{
+       struct intel_wakeref_auto *wf = from_timer(wf, t, timer);
+       intel_wakeref_t wakeref;
+       unsigned long flags;
+
+       if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
+               return;
+
+       wakeref = fetch_and_zero(&wf->wakeref);
+       spin_unlock_irqrestore(&wf->lock, flags);
+
+       intel_runtime_pm_put(wf->i915, 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 = 0;
+       wf->i915 = i915;
+}
+
+void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
+{
+       unsigned long flags;
+
+       if (!timeout) {
+               if (del_timer_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);
+
+       if (!refcount_inc_not_zero(&wf->count)) {
+               spin_lock_irqsave(&wf->lock, flags);
+               if (!refcount_read(&wf->count)) {
+                       GEM_BUG_ON(wf->wakeref);
+                       wf->wakeref = intel_runtime_pm_get_if_in_use(wf->i915);
+               }
+               refcount_inc(&wf->count);
+               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);
+       GEM_BUG_ON(wf->wakeref);
+}

diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
index db742291211cfc7625db020eeaa7209f2e30092b..8a5f85c000ce3aff70ec08ae63c1689003f7e0d6 100644 (file)
--- a/drivers/gpu/drm/i915/intel_wakeref.h
+++ b/drivers/gpu/drm/i915/intel_wakeref.h
@@ -9,7 +9,9 @@
 
 #include <linux/atomic.h>
 #include <linux/mutex.h>
+#include <linux/refcount.h>
 #include <linux/stackdepot.h>
+#include <linux/timer.h>
 
 struct drm_i915_private;
 
@@ -130,4 +132,33 @@ intel_wakeref_active(struct intel_wakeref *wf)
        return READ_ONCE(wf->wakeref);
 }
 
+struct intel_wakeref_auto {
+       struct drm_i915_private *i915;
+       struct timer_list timer;
+       intel_wakeref_t wakeref;
+       spinlock_t lock;
+       refcount_t count;
+};
+
+/**
+ * intel_wakeref_auto: Delay the runtime-pm autosuspend
+ * @wf: the wakeref
+ * @timeout: relative timeout in jiffies
+ *
+ * The runtime-pm core uses a suspend delay after the last wakeref
+ * is released before triggering runtime suspend of the device. That
+ * delay is configurable via sysfs with little regard to the device
+ * characteristics. Instead, we want to tune the autosuspend based on our
+ * HW knowledge. intel_wakeref_auto() delays the sleep by the supplied
+ * timeout.
+ *
+ * Pass @timeout = 0 to cancel a previous autosuspend by executing the
+ * suspend immediately.
+ */
+void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout);
+
+void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
+                            struct drm_i915_private *i915);
+void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf);
+
 #endif /* INTEL_WAKEREF_H */