drm/vc4: Implement custom atomic commit in vc4.

This is just drm_atomic_helper_commit(), with wait_for_fence replaced
with V3D seqno waits based on msm's atomic commit's wait loop.

This means we now synchronize to our own rendering.  The old
wait_for_fence loop did nothing since we never attached a dmabuf fence
to our plane state.

Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 90 insertions, 1 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index 98b57bd0fc80..e498696fe21f 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -7,15 +7,104 @@
  */
 
 #include "drm_crtc.h"
+#include "drm_atomic.h"
 #include "drm_atomic_helper.h"
 #include "drm_crtc_helper.h"
 #include "drm_plane_helper.h"
 #include "drm_fb_cma_helper.h"
 #include "vc4_drv.h"
 
+
+/**
+ * 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)
+{
+	int ret;
+	int i;
+	uint64_t wait_seqno = 0;
+
+	if (async) {
+		DRM_ERROR("async\n");
+		return -EBUSY;
+	}
+
+	ret = drm_atomic_helper_prepare_planes(dev, state);
+	if (ret)
+		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;
+			struct vc4_bo *bo;
+			cma_bo = drm_fb_cma_get_gem_obj(plane->state->fb, 0);
+			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.
+	 */
+
+	vc4_wait_for_seqno(dev, wait_seqno, ~0ull, false);
+
+	drm_atomic_helper_commit_modeset_disables(dev, state);
+
+	drm_atomic_helper_commit_planes(dev, state);
+
+	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);
+
+	return 0;
+}
+
 static const struct drm_mode_config_funcs vc4_mode_funcs = {
 	.atomic_check = drm_atomic_helper_check,
-	.atomic_commit = drm_atomic_helper_commit,
+	.atomic_commit = vc4_atomic_commit,
 	.fb_create = drm_fb_cma_create,
 };