[RFC PATCH 04/11] drm: Add __drm_framebuffer_remove_atomic

[Brian Starkey]

Implement the CRTC/Plane disable functionality of drm_framebuffer_remove
using the atomic API, and use it if possible.

For atomic drivers, this removes the possibility of several commits when
a framebuffer is in use by more than one CRTC/plane.

Additionally, this will provide a suitable place to support the removal
of a framebuffer from a writeback connector, in the case that a
writeback connector is still actively using a framebuffer when it is
removed by userspace.

Signed-off-by: Brian Starkey <brian.starkey at arm.com>
---
 drivers/gpu/drm/drm_framebuffer.c |  154 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 152 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index 528f75d..b02cf73 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -22,6 +22,7 @@
 
 #include <linux/export.h>
 #include <drm/drmP.h>
+#include <drm/drm_atomic.h>
 #include <drm/drm_auth.h>
 #include <drm/drm_framebuffer.h>
 
@@ -795,6 +796,148 @@ void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
 EXPORT_SYMBOL(drm_framebuffer_cleanup);
 
 /**
+ * __drm_framebuffer_remove_atomic - atomic version of __drm_framebuffer_remove
+ * @dev: drm device
+ * @fb: framebuffer to remove
+ *
+ * If the driver implements the atomic API, we can handle the disabling of all
+ * CRTCs/planes which use a framebuffer which is going away in a single atomic
+ * commit.
+ *
+ * This scans all CRTCs and planes in @dev's mode_config. If they're using @fb,
+ * it is removed and the CRTC/plane disabled.
+ * The legacy references are dropped and the ->fb pointers set to NULL
+ * accordingly.
+ *
+ * Returns:
+ * true if the framebuffer was successfully removed from use
+ */
+static bool __drm_framebuffer_remove_atomic(struct drm_device *dev,
+		struct drm_framebuffer *fb)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	struct drm_atomic_state *state;
+	struct drm_connector_state *conn_state;
+	struct drm_connector *connector;
+	struct drm_plane *plane;
+	struct drm_crtc *crtc;
+	unsigned plane_mask;
+	int i, ret;
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state)
+		return false;
+
+	state->acquire_ctx = &ctx;
+
+retry:
+	drm_for_each_crtc(crtc, dev) {
+		struct drm_plane_state *primary_state;
+		struct drm_crtc_state *crtc_state;
+
+		primary_state = drm_atomic_get_plane_state(state, crtc->primary);
+		if (IS_ERR(primary_state)) {
+			ret = PTR_ERR(primary_state);
+			goto fail;
+		}
+
+		if (primary_state->fb != fb)
+			continue;
+
+		crtc_state = drm_atomic_get_crtc_state(state, crtc);
+		if (IS_ERR(crtc_state)) {
+			ret = PTR_ERR(crtc_state);
+			goto fail;
+		}
+
+		/* Only handle the CRTC itself here, handle the plane later */
+		ret = drm_atomic_set_mode_for_crtc(crtc_state, NULL);
+		if (ret != 0)
+			goto fail;
+
+		crtc_state->active = false;
+
+		/* Get the connectors in order to disable them */
+		ret = drm_atomic_add_affected_connectors(state, crtc);
+		if (ret)
+			goto fail;
+	}
+
+	plane_mask = 0;
+	drm_for_each_plane(plane, dev) {
+		struct drm_plane_state *plane_state;
+
+		plane_state = drm_atomic_get_plane_state(state, plane);
+		if (IS_ERR(plane_state)) {
+			ret = PTR_ERR(plane_state);
+			goto fail;
+		}
+
+		if (plane_state->fb != fb)
+			continue;
+
+		plane->old_fb = plane->fb;
+		plane_mask |= 1 << drm_plane_index(plane);
+
+		/*
+		 * Open-coded copy of __drm_atomic_helper_disable_plane to avoid
+		 * a dependency on atomic-helper
+		 */
+		ret = drm_atomic_set_crtc_for_plane(plane_state, NULL);
+		if (ret != 0)
+			goto fail;
+
+		drm_atomic_set_fb_for_plane(plane_state, NULL);
+		plane_state->crtc_x = 0;
+		plane_state->crtc_y = 0;
+		plane_state->crtc_w = 0;
+		plane_state->crtc_h = 0;
+		plane_state->src_x = 0;
+		plane_state->src_y = 0;
+		plane_state->src_w = 0;
+		plane_state->src_h = 0;
+	}
+
+	/* All of the connectors in state need disabling */
+	for_each_connector_in_state(state, connector, conn_state, i) {
+		ret = drm_atomic_set_crtc_for_connector(conn_state,
+							NULL);
+		if (ret)
+			goto fail;
+	}
+
+	if (WARN_ON(!plane_mask)) {
+		DRM_ERROR("Couldn't find any usage of [FB:%d]\n", fb->base.id);
+		ret = -ENOENT;
+		goto fail;
+	}
+
+	ret = drm_atomic_commit(state);
+
+fail:
+	drm_atomic_clean_old_fb(dev, plane_mask, ret);
+
+	if (ret == -EDEADLK)
+		goto backoff;
+
+	if (ret != 0)
+		drm_atomic_state_free(state);
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+
+	return ret ? false : true;
+
+backoff:
+	drm_atomic_state_clear(state);
+	drm_modeset_backoff(&ctx);
+
+	goto retry;
+}
+
+/**
  * __drm_framebuffer_remove - remove all usage of a framebuffer object
  * @dev: drm device
  * @fb: framebuffer to remove
@@ -869,9 +1012,16 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb)
 	 * in-use fb with fb-id == 0. Userspace is allowed to shoot its own foot
 	 * in this manner.
 	 */
-	if (drm_framebuffer_read_refcount(fb) > 1)
-		if (!__drm_framebuffer_remove(dev, fb))
+	if (drm_framebuffer_read_refcount(fb) > 1) {
+		bool removed;
+		if (dev->mode_config.funcs->atomic_commit)
+			removed = __drm_framebuffer_remove_atomic(dev, fb);
+		else
+			removed = __drm_framebuffer_remove(dev, fb);
+
+		if (!removed)
 			DRM_ERROR("failed to remove fb from active usage\n");
+	}
 
 	drm_framebuffer_unreference(fb);
 }
-- 
1.7.9.5