From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 23 Jan 2020 22:44:59 +0000 (+0000)
Subject: drm/i915: Wait on vma activity before taking the mutex
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=d62f416f925dc615256193c76aebd582ae88bcaf;p=openwrt%2Fstaging%2Fblogic.git

drm/i915: Wait on vma activity before taking the mutex

Optimistically wait for the prior vma activity before taking the mutex
to minimise the mutex hold time while unbinding. We will then verify the
vma is idle with a second wait under the mutex to ensure it is safe to
unbind.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123224459.38128-2-chris@chris-wilson.co.uk
---

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 4999882fbceb..84e03da0d5f9 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1279,16 +1279,21 @@ int i915_vma_unbind(struct i915_vma *vma)
 		/* XXX not always required: nop_clear_range */
 		wakeref = intel_runtime_pm_get(&vm->i915->runtime_pm);
 
+	/* Optimistic wait before taking the mutex */
+	err = i915_vma_sync(vma);
+	if (err)
+		goto out_rpm;
+
 	err = mutex_lock_interruptible(&vm->mutex);
 	if (err)
-		return err;
+		goto out_rpm;
 
 	err = __i915_vma_unbind(vma);
 	mutex_unlock(&vm->mutex);
 
+out_rpm:
 	if (wakeref)
 		intel_runtime_pm_put(&vm->i915->runtime_pm, wakeref);
-
 	return err;
 }