Commit b27e35ae authored by Chris Wilson's avatar Chris Wilson
Browse files

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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190527115114.13448-1-chris@chris-wilson.co.uk
parent c457d9cf

drivers/gpu/drm/i915/Kconfig.profile

+14 −0
Original line number Diff line number Diff line 
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

drivers/gpu/drm/i915/i915_drv.h

+3 −0
Original line number Diff line number Diff line
@@ -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.

	 */

drivers/gpu/drm/i915/i915_gem.c

+7 −0
Original line number Diff line number Diff line
@@ -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);

}

drivers/gpu/drm/i915/i915_gem_pm.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

drivers/gpu/drm/i915/intel_wakeref.c

+63 −0
Original line number Diff line number Diff line
@@ -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);

}

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