[PATCH v2 8/9] drm/vc4: Add support for async pageflips.

[Eric Anholt]

An async pageflip stores the modeset to be done and executes it once
the BOs are ready to be displayed.  This gets us about 3x performance
in full screen rendering with pageflipping.

Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
---
 drivers/gpu/drm/vc4/vc4_crtc.c  |  99 +++++++++++++++++++++++++-
 drivers/gpu/drm/vc4/vc4_drv.h   |  16 +++++
 drivers/gpu/drm/vc4/vc4_gem.c   |  40 +++++++++++
 drivers/gpu/drm/vc4/vc4_kms.c   | 149 +++++++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/vc4/vc4_plane.c |  40 +++++++++++
 5 files changed, 342 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 7a9f476..a319332 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -35,6 +35,7 @@
 #include "drm_atomic_helper.h"
 #include "drm_crtc_helper.h"
 #include "linux/clk.h"
+#include "drm_fb_cma_helper.h"
 #include "linux/component.h"
 #include "linux/of_device.h"
 #include "vc4_drv.h"
@@ -475,10 +476,106 @@ static irqreturn_t vc4_crtc_irq_handler(int irq, void *data)
 	return ret;
 }
 
+struct vc4_async_flip_state {
+	struct drm_crtc *crtc;
+	struct drm_framebuffer *fb;
+	struct drm_pending_vblank_event *event;
+
+	struct vc4_seqno_cb cb;
+};
+
+/* Called when the V3D execution for the BO being flipped to is done, so that
+ * we can actually update the plane's address to point to it.
+ */
+static void
+vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
+{
+	struct vc4_async_flip_state *flip_state =
+		container_of(cb, struct vc4_async_flip_state, cb);
+	struct drm_crtc *crtc = flip_state->crtc;
+	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct drm_plane *plane = crtc->primary;
+
+	vc4_plane_async_set_fb(plane, flip_state->fb);
+	if (flip_state->event) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&dev->event_lock, flags);
+		drm_crtc_send_vblank_event(crtc, flip_state->event);
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+	}
+
+	drm_framebuffer_unreference(flip_state->fb);
+	kfree(flip_state);
+
+	up(&vc4->async_modeset);
+}
+
+/* Implements async (non-vblank-synced) page flips.
+ *
+ * The page flip ioctl needs to return immediately, so we grab the
+ * modeset semaphore on the pipe, and queue the address update for
+ * when V3D is done with the BO being flipped to.
+ */
+static int vc4_async_page_flip(struct drm_crtc *crtc,
+			       struct drm_framebuffer *fb,
+			       struct drm_pending_vblank_event *event,
+			       uint32_t flags)
+{
+	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct drm_plane *plane = crtc->primary;
+	int ret = 0;
+	struct vc4_async_flip_state *flip_state;
+	struct drm_gem_cma_object *cma_bo = drm_fb_cma_get_gem_obj(fb, 0);
+	struct vc4_bo *bo = to_vc4_bo(&cma_bo->base);
+
+	flip_state = kzalloc(sizeof(*flip_state), GFP_KERNEL);
+	if (!flip_state)
+		return -ENOMEM;
+
+	drm_framebuffer_reference(fb);
+	flip_state->fb = fb;
+	flip_state->crtc = crtc;
+	flip_state->event = event;
+
+	/* Make sure all other async modesetes have landed. */
+	ret = down_interruptible(&vc4->async_modeset);
+	if (ret) {
+		kfree(flip_state);
+		return ret;
+	}
+
+	/* Immediately update the plane's legacy fb pointer, so that later
+	 * modeset prep sees the state that will be present when the semaphore
+	 * is released.
+	 */
+	drm_atomic_set_fb_for_plane(plane->state, fb);
+	plane->fb = fb;
+
+	vc4_queue_seqno_cb(dev, &flip_state->cb, bo->seqno,
+			   vc4_async_page_flip_complete);
+
+	/* Driver takes ownership of state on successful async commit. */
+	return 0;
+}
+
+static int vc4_page_flip(struct drm_crtc *crtc,
+			 struct drm_framebuffer *fb,
+			 struct drm_pending_vblank_event *event,
+			 uint32_t flags)
+{
+	if (flags & DRM_MODE_PAGE_FLIP_ASYNC)
+		return vc4_async_page_flip(crtc, fb, event, flags);
+	else
+		return drm_atomic_helper_page_flip(crtc, fb, event, flags);
+}
+
 static const struct drm_crtc_funcs vc4_crtc_funcs = {
 	.set_config = drm_atomic_helper_set_config,
 	.destroy = vc4_crtc_destroy,
-	.page_flip = drm_atomic_helper_page_flip,
+	.page_flip = vc4_page_flip,
 	.set_property = NULL,
 	.cursor_set = NULL, /* handled by drm_mode_cursor_universal */
 	.cursor_move = NULL, /* handled by drm_mode_cursor_universal */
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 0bc8c57..f9927d8 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -76,6 +76,11 @@ struct vc4_dev {
 	wait_queue_head_t job_wait_queue;
 	struct work_struct job_done_work;
 
+	/* List of struct vc4_seqno_cb for callbacks to be made from a
+	 * workqueue when the given seqno is passed.
+	 */
+	struct list_head seqno_cb_list;
+
 	/* The binner overflow memory that's currently set up in
 	 * BPOA/BPOS registers.  When overflow occurs and a new one is
 	 * allocated, the previous one will be moved to
@@ -128,6 +133,12 @@ to_vc4_bo(struct drm_gem_object *bo)
 	return (struct vc4_bo *)bo;
 }
 
+struct vc4_seqno_cb {
+	struct work_struct work;
+	uint64_t seqno;
+	void (*func)(struct vc4_seqno_cb *cb);
+};
+
 struct vc4_v3d {
 	struct platform_device *pdev;
 	void __iomem *regs;
@@ -384,6 +395,9 @@ void vc4_submit_next_job(struct drm_device *dev);
 int vc4_wait_for_seqno(struct drm_device *dev, uint64_t seqno,
 		       uint64_t timeout_ns, bool interruptible);
 void vc4_job_handle_completed(struct vc4_dev *vc4);
+int vc4_queue_seqno_cb(struct drm_device *dev,
+		       struct vc4_seqno_cb *cb, uint64_t seqno,
+		       void (*func)(struct vc4_seqno_cb *cb));
 
 /* vc4_hdmi.c */
 extern struct platform_driver vc4_hdmi_driver;
@@ -409,6 +423,8 @@ struct drm_plane *vc4_plane_init(struct drm_device *dev,
 				 enum drm_plane_type type);
 u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist);
 u32 vc4_plane_dlist_size(struct drm_plane_state *state);
+void vc4_plane_async_set_fb(struct drm_plane *plane,
+			    struct drm_framebuffer *fb);
 
 /* vc4_v3d.c */
 extern struct platform_driver vc4_v3d_driver;
diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c
index 936dddf..5fb0556 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -461,6 +461,7 @@ void
 vc4_job_handle_completed(struct vc4_dev *vc4)
 {
 	unsigned long irqflags;
+	struct vc4_seqno_cb *cb, *cb_temp;
 
 	spin_lock_irqsave(&vc4->job_lock, irqflags);
 	while (!list_empty(&vc4->job_done_list)) {
@@ -473,7 +474,45 @@ vc4_job_handle_completed(struct vc4_dev *vc4)
 		vc4_complete_exec(vc4->dev, exec);
 		spin_lock_irqsave(&vc4->job_lock, irqflags);
 	}
+
+	list_for_each_entry_safe(cb, cb_temp, &vc4->seqno_cb_list, work.entry) {
+		if (cb->seqno <= vc4->finished_seqno) {
+			list_del_init(&cb->work.entry);
+			schedule_work(&cb->work);
+		}
+	}
+
+	spin_unlock_irqrestore(&vc4->job_lock, irqflags);
+}
+
+static void vc4_seqno_cb_work(struct work_struct *work)
+{
+	struct vc4_seqno_cb *cb = container_of(work, struct vc4_seqno_cb, work);
+
+	cb->func(cb);
+}
+
+int vc4_queue_seqno_cb(struct drm_device *dev,
+		       struct vc4_seqno_cb *cb, uint64_t seqno,
+		       void (*func)(struct vc4_seqno_cb *cb))
+{
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	int ret = 0;
+	unsigned long irqflags;
+
+	cb->func = func;
+	INIT_WORK(&cb->work, vc4_seqno_cb_work);
+
+	spin_lock_irqsave(&vc4->job_lock, irqflags);
+	if (seqno > vc4->finished_seqno) {
+		cb->seqno = seqno;
+		list_add_tail(&cb->work.entry, &vc4->seqno_cb_list);
+	} else {
+		schedule_work(&cb->work);
+	}
 	spin_unlock_irqrestore(&vc4->job_lock, irqflags);
+
+	return ret;
 }
 
 /* Scheduled when any job has been completed, this walks the list of
@@ -610,6 +649,7 @@ vc4_gem_init(struct drm_device *dev)
 
 	INIT_LIST_HEAD(&vc4->job_list);
 	INIT_LIST_HEAD(&vc4->job_done_list);
+	INIT_LIST_HEAD(&vc4->seqno_cb_list);
 	spin_lock_init(&vc4->job_lock);
 
 	INIT_WORK(&vc4->hangcheck.reset_work, vc4_reset_work);
diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index 2e5597d..f95f2df 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -15,6 +15,7 @@
  */
 
 #include "drm_crtc.h"
+#include "drm_atomic.h"
 #include "drm_atomic_helper.h"
 #include "drm_crtc_helper.h"
 #include "drm_plane_helper.h"
@@ -29,10 +30,152 @@ static void vc4_output_poll_changed(struct drm_device *dev)
 		drm_fbdev_cma_hotplug_event(vc4->fbdev);
 }
 
+struct vc4_commit {
+	struct drm_device *dev;
+	struct drm_atomic_state *state;
+	struct vc4_seqno_cb cb;
+};
+
+static void
+vc4_atomic_complete_commit(struct vc4_commit *c)
+{
+	struct drm_atomic_state *state = c->state;
+	struct drm_device *dev = state->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+
+	drm_atomic_helper_commit_modeset_disables(dev, state);
+
+	drm_atomic_helper_commit_planes(dev, state, false);
+
+	drm_atomic_helper_commit_modeset_enables(dev, state);
+
+	drm_atomic_helper_wait_for_vblanks(dev, state);
+
+	drm_atomic_helper_cleanup_planes(dev, state);
+
+	drm_atomic_state_free(state);
+
+	up(&vc4->async_modeset);
+
+	kfree(c);
+}
+
+static void
+vc4_atomic_complete_commit_seqno_cb(struct vc4_seqno_cb *cb)
+{
+	struct vc4_commit *c = container_of(cb, struct vc4_commit, cb);
+
+	vc4_atomic_complete_commit(c);
+}
+
+static struct vc4_commit *commit_init(struct drm_atomic_state *state)
+{
+	struct vc4_commit *c = kzalloc(sizeof(*c), GFP_KERNEL);
+
+	if (!c)
+		return NULL;
+	c->dev = state->dev;
+	c->state = state;
+
+	return c;
+}
+
+/**
+ * vc4_atomic_commit - commit validated state object
+ * @dev: DRM device
+ * @state: the driver state object
+ * @async: asynchronous commit
+ *
+ * This function commits a with drm_atomic_helper_check() pre-validated state
+ * object. This can still fail when e.g. the framebuffer reservation fails. For
+ * now this doesn't implement asynchronous commits.
+ *
+ * RETURNS
+ * Zero for success or -errno.
+ */
+static int vc4_atomic_commit(struct drm_device *dev,
+			     struct drm_atomic_state *state,
+			     bool async)
+{
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	int ret;
+	int i;
+	uint64_t wait_seqno = 0;
+	struct vc4_commit *c;
+
+	c = commit_init(state);
+	if (!c)
+		return -ENOMEM;
+
+	/* Make sure that any outstanding modesets have finished. */
+	ret = down_interruptible(&vc4->async_modeset);
+	if (ret) {
+		kfree(c);
+		return ret;
+	}
+
+	ret = drm_atomic_helper_prepare_planes(dev, state);
+	if (ret) {
+		kfree(c);
+		up(&vc4->async_modeset);
+		return ret;
+	}
+
+	for (i = 0; i < dev->mode_config.num_total_plane; i++) {
+		struct drm_plane *plane = state->planes[i];
+		struct drm_plane_state *new_state = state->plane_states[i];
+
+		if (!plane)
+			continue;
+
+		if ((plane->state->fb != new_state->fb) && new_state->fb) {
+			struct drm_gem_cma_object *cma_bo =
+				drm_fb_cma_get_gem_obj(new_state->fb, 0);
+			struct vc4_bo *bo = to_vc4_bo(&cma_bo->base);
+
+			wait_seqno = max(bo->seqno, wait_seqno);
+		}
+	}
+
+	/*
+	 * This is the point of no return - everything below never fails except
+	 * when the hw goes bonghits. Which means we can commit the new state on
+	 * the software side now.
+	 */
+
+	drm_atomic_helper_swap_state(dev, state);
+
+	/*
+	 * Everything below can be run asynchronously without the need to grab
+	 * any modeset locks at all under one condition: It must be guaranteed
+	 * that the asynchronous work has either been cancelled (if the driver
+	 * supports it, which at least requires that the framebuffers get
+	 * cleaned up with drm_atomic_helper_cleanup_planes()) or completed
+	 * before the new state gets committed on the software side with
+	 * drm_atomic_helper_swap_state().
+	 *
+	 * This scheme allows new atomic state updates to be prepared and
+	 * checked in parallel to the asynchronous completion of the previous
+	 * update. Which is important since compositors need to figure out the
+	 * composition of the next frame right after having submitted the
+	 * current layout.
+	 */
+
+	if (async) {
+		vc4_queue_seqno_cb(dev, &c->cb, wait_seqno,
+				   vc4_atomic_complete_commit_seqno_cb);
+	} else {
+		vc4_wait_for_seqno(dev, wait_seqno, ~0ull, false);
+		vc4_atomic_complete_commit(c);
+	}
+
+	return 0;
+}
+
 static const struct drm_mode_config_funcs vc4_mode_funcs = {
 	.output_poll_changed = vc4_output_poll_changed,
 	.atomic_check = drm_atomic_helper_check,
-	.atomic_commit = drm_atomic_helper_commit,
+	.atomic_commit = vc4_atomic_commit,
 	.fb_create = drm_fb_cma_create,
 };
 
@@ -41,6 +184,8 @@ int vc4_kms_load(struct drm_device *dev)
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	int ret;
 
+	sema_init(&vc4->async_modeset, 1);
+
 	ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
 	if (ret < 0) {
 		dev_err(dev->dev, "failed to initialize vblank\n");
@@ -51,6 +196,8 @@ int vc4_kms_load(struct drm_device *dev)
 	dev->mode_config.max_height = 2048;
 	dev->mode_config.funcs = &vc4_mode_funcs;
 	dev->mode_config.preferred_depth = 24;
+	dev->mode_config.async_page_flip = true;
+
 	dev->vblank_disable_allowed = true;
 
 	drm_mode_config_reset(dev);
diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index cdd8b10..db32c373 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -29,6 +29,14 @@ struct vc4_plane_state {
 	u32 *dlist;
 	u32 dlist_size; /* Number of dwords in allocated for the display list */
 	u32 dlist_count; /* Number of used dwords in the display list. */
+
+	/* Offset in the dlist to pointer word 0. */
+	u32 pw0_offset;
+
+	/* Offset where the plane's dlist was last stored in the
+	   hardware at vc4_crtc_atomic_flush() time.
+	*/
+	u32 *hw_dlist;
 };
 
 static inline struct vc4_plane_state *
@@ -197,6 +205,8 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 	/* Position Word 3: Context.  Written by the HVS. */
 	vc4_dlist_write(vc4_state, 0xc0c0c0c0);
 
+	vc4_state->pw0_offset = vc4_state->dlist_count;
+
 	/* Pointer Word 0: RGB / Y Pointer */
 	vc4_dlist_write(vc4_state, bo->paddr + offset);
 
@@ -248,6 +258,8 @@ u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist)
 	struct vc4_plane_state *vc4_state = to_vc4_plane_state(plane->state);
 	int i;
 
+	vc4_state->hw_dlist = dlist;
+
 	/* Can't memcpy_toio() because it needs to be 32-bit writes. */
 	for (i = 0; i < vc4_state->dlist_count; i++)
 		writel(vc4_state->dlist[i], &dlist[i]);
@@ -262,6 +274,34 @@ u32 vc4_plane_dlist_size(struct drm_plane_state *state)
 	return vc4_state->dlist_count;
 }
 
+/* Updates the plane to immediately (well, once the FIFO needs
+ * refilling) scan out from at a new framebuffer.
+ */
+void vc4_plane_async_set_fb(struct drm_plane *plane, struct drm_framebuffer *fb)
+{
+	struct vc4_plane_state *vc4_state = to_vc4_plane_state(plane->state);
+	struct drm_gem_cma_object *bo = drm_fb_cma_get_gem_obj(fb, 0);
+	uint32_t addr;
+
+	/* We're skipping the address adjustment for negative origin,
+	 * because this is only called on the primary plane.
+	 */
+	WARN_ON_ONCE(plane->state->crtc_x < 0 || plane->state->crtc_y < 0);
+	addr = bo->paddr + fb->offsets[0];
+
+	/* Write the new address into the hardware immediately.  The
+	 * scanout will start from this address as soon as the FIFO
+	 * needs to refill with pixels.
+	 */
+	writel(addr, &vc4_state->hw_dlist[vc4_state->pw0_offset]);
+
+	/* Also update the CPU-side dlist copy, so that any later
+	 * atomic updates that don't do a new modeset on our plane
+	 * also use our updated address.
+	 */
+	vc4_state->dlist[vc4_state->pw0_offset] = addr;
+}
+
 static const struct drm_plane_helper_funcs vc4_plane_helper_funcs = {
 	.prepare_fb = NULL,
 	.cleanup_fb = NULL,
-- 
2.6.2

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