drm/i915: Perform object clflushing asynchronously

Flushing the cachelines for an object is slow, can be as much as 100ms
for a large framebuffer. We currently do this under the struct_mutex BKL
on execution or on pageflip. But now with the ability to add fences to
obj->resv for both flips and execbuf (and we naturally wait on the fence
before CPU access), we can move the clflush operation to a workqueue and
signal a fence for completion, thereby doing the work asynchronously and
not blocking the driver or its clients.

v2: Introduce i915_gem_clflush.h and use a new name, split out some
extras into separate patches.

Suggested-by: Akash Goel <akash.goel@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170222114049.28456-5-chris@chris-wilson.co.uk

1 files changed, 189 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_clflush.c b/drivers/gpu/drm/i915/i915_gem_clflush.c
new file mode 100644
index 000000000000..c5fee02f3173
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_gem_clflush.c
@@ -0,0 +1,189 @@
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#include "i915_drv.h"
+#include "intel_frontbuffer.h"
+#include "i915_gem_clflush.h"
+
+static DEFINE_SPINLOCK(clflush_lock);
+static u64 clflush_context;
+
+struct clflush {
+	struct dma_fence dma; /* Must be first for dma_fence_free() */
+	struct i915_sw_fence wait;
+	struct work_struct work;
+	struct drm_i915_gem_object *obj;
+};
+
+static const char *i915_clflush_get_driver_name(struct dma_fence *fence)
+{
+	return DRIVER_NAME;
+}
+
+static const char *i915_clflush_get_timeline_name(struct dma_fence *fence)
+{
+	return "clflush";
+}
+
+static bool i915_clflush_enable_signaling(struct dma_fence *fence)
+{
+	return true;
+}
+
+static void i915_clflush_release(struct dma_fence *fence)
+{
+	struct clflush *clflush = container_of(fence, typeof(*clflush), dma);
+
+	i915_sw_fence_fini(&clflush->wait);
+
+	BUILD_BUG_ON(offsetof(typeof(*clflush), dma));
+	dma_fence_free(&clflush->dma);
+}
+
+static const struct dma_fence_ops i915_clflush_ops = {
+	.get_driver_name = i915_clflush_get_driver_name,
+	.get_timeline_name = i915_clflush_get_timeline_name,
+	.enable_signaling = i915_clflush_enable_signaling,
+	.wait = dma_fence_default_wait,
+	.release = i915_clflush_release,
+};
+
+static void __i915_do_clflush(struct drm_i915_gem_object *obj)
+{
+	drm_clflush_sg(obj->mm.pages);
+	obj->cache_dirty = false;
+
+	intel_fb_obj_flush(obj, false, ORIGIN_CPU);
+}
+
+static void i915_clflush_work(struct work_struct *work)
+{
+	struct clflush *clflush = container_of(work, typeof(*clflush), work);
+	struct drm_i915_gem_object *obj = clflush->obj;
+
+	if (!obj->cache_dirty)
+		goto out;
+
+	if (i915_gem_object_pin_pages(obj)) {
+		DRM_ERROR("Failed to acquire obj->pages for clflushing\n");
+		goto out;
+	}
+
+	__i915_do_clflush(obj);
+
+	i915_gem_object_unpin_pages(obj);
+
+out:
+	i915_gem_object_put(obj);
+
+	dma_fence_signal(&clflush->dma);
+	dma_fence_put(&clflush->dma);
+}
+
+static int __i915_sw_fence_call
+i915_clflush_notify(struct i915_sw_fence *fence,
+		    enum i915_sw_fence_notify state)
+{
+	struct clflush *clflush = container_of(fence, typeof(*clflush), wait);
+
+	switch (state) {
+	case FENCE_COMPLETE:
+		schedule_work(&clflush->work);
+		break;
+
+	case FENCE_FREE:
+		dma_fence_put(&clflush->dma);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+void i915_gem_clflush_object(struct drm_i915_gem_object *obj,
+			     unsigned int flags)
+{
+	struct clflush *clflush;
+
+	/*
+	 * Stolen memory is always coherent with the GPU as it is explicitly
+	 * marked as wc by the system, or the system is cache-coherent.
+	 * Similarly, we only access struct pages through the CPU cache, so
+	 * anything not backed by physical memory we consider to be always
+	 * coherent and not need clflushing.
+	 */
+	if (!i915_gem_object_has_struct_page(obj))
+		return;
+
+	obj->cache_dirty = true;
+
+	/* If the GPU is snooping the contents of the CPU cache,
+	 * we do not need to manually clear the CPU cache lines.  However,
+	 * the caches are only snooped when the render cache is
+	 * flushed/invalidated.  As we always have to emit invalidations
+	 * and flushes when moving into and out of the RENDER domain, correct
+	 * snooping behaviour occurs naturally as the result of our domain
+	 * tracking.
+	 */
+	if (!(flags & I915_CLFLUSH_FORCE) && i915_gem_object_is_coherent(obj))
+		return;
+
+	trace_i915_gem_object_clflush(obj);
+
+	clflush = NULL;
+	if (!(flags & I915_CLFLUSH_SYNC))
+		clflush = kmalloc(sizeof(*clflush), GFP_KERNEL);
+	if (clflush) {
+		dma_fence_init(&clflush->dma,
+			       &i915_clflush_ops,
+			       &clflush_lock,
+			       clflush_context,
+			       0);
+		i915_sw_fence_init(&clflush->wait, i915_clflush_notify);
+
+		clflush->obj = i915_gem_object_get(obj);
+		INIT_WORK(&clflush->work, i915_clflush_work);
+
+		dma_fence_get(&clflush->dma);
+
+		i915_sw_fence_await_reservation(&clflush->wait,
+						obj->resv, NULL,
+						false, I915_FENCE_TIMEOUT,
+						GFP_KERNEL);
+
+		reservation_object_lock(obj->resv, NULL);
+		reservation_object_add_excl_fence(obj->resv, &clflush->dma);
+		reservation_object_unlock(obj->resv);
+
+		i915_sw_fence_commit(&clflush->wait);
+	} else if (obj->mm.pages) {
+		__i915_do_clflush(obj);
+	} else {
+		GEM_BUG_ON(obj->base.write_domain != I915_GEM_DOMAIN_CPU);
+	}
+}
+
+void i915_gem_clflush_init(struct drm_i915_private *i915)
+{
+	clflush_context = dma_fence_context_alloc(1);
+}