+/*
+ * Atomic hardware plane allocator
+ *
+ * The hardware plane allocator is solely based on the atomic plane states
+ * without keeping any external state to avoid races between .atomic_check()
+ * and .atomic_commit().
+ *
+ * The core idea is to avoid using a free planes bitmask that would need to be
+ * shared between check and commit handlers with a collective knowledge based on
+ * the allocated hardware plane(s) for each KMS plane. The allocator then loops
+ * over all plane states to compute the free planes bitmask, allocates hardware
+ * planes based on that bitmask, and stores the result back in the plane states.
+ *
+ * For this to work we need to access the current state of planes not touched by
+ * the atomic update. To ensure that it won't be modified, we need to lock all
+ * planes using drm_atomic_get_plane_state(). This effectively serializes atomic
+ * updates from .atomic_check() up to completion (when swapping the states if
+ * the check step has succeeded) or rollback (when freeing the states if the
+ * check step has failed).
+ *
+ * Allocation is performed in the .atomic_check() handler and applied
+ * automatically when the core swaps the old and new states.
+ */
+
+static bool rcar_du_plane_needs_realloc(struct rcar_du_plane *plane,
+ struct rcar_du_plane_state *state)
+{
+ const struct rcar_du_format_info *cur_format;
+
+ cur_format = to_rcar_du_plane_state(plane->plane.state)->format;
+
+ /* Lowering the number of planes doesn't strictly require reallocation
+ * as the extra hardware plane will be freed when committing, but doing
+ * so could lead to more fragmentation.
+ */
+ return !cur_format || cur_format->planes != state->format->planes;
+}
+
+static unsigned int rcar_du_plane_hwmask(struct rcar_du_plane_state *state)
+{
+ unsigned int mask;
+
+ if (state->hwindex == -1)
+ return 0;
+
+ mask = 1 << state->hwindex;
+ if (state->format->planes == 2)
+ mask |= 1 << ((state->hwindex + 1) % 8);
+
+ return mask;
+}
+
+static int rcar_du_plane_hwalloc(unsigned int num_planes, unsigned int free)
+{
+ unsigned int i;
+
+ for (i = 0; i < RCAR_DU_NUM_HW_PLANES; ++i) {
+ if (!(free & (1 << i)))
+ continue;
+
+ if (num_planes == 1 || free & (1 << ((i + 1) % 8)))
+ break;
+ }
+
+ return i == RCAR_DU_NUM_HW_PLANES ? -EBUSY : i;
+}
+
+static int rcar_du_atomic_check(struct drm_device *dev,
+ struct drm_atomic_state *state)
+{
+ struct rcar_du_device *rcdu = dev->dev_private;
+ unsigned int group_freed_planes[RCAR_DU_MAX_GROUPS] = { 0, };
+ unsigned int group_free_planes[RCAR_DU_MAX_GROUPS] = { 0, };
+ bool needs_realloc = false;
+ unsigned int groups = 0;
+ unsigned int i;
+ int ret;
+
+ ret = drm_atomic_helper_check(dev, state);
+ if (ret < 0)
+ return ret;
+
+ /* Check if hardware planes need to be reallocated. */
+ for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
+ struct rcar_du_plane_state *plane_state;
+ struct rcar_du_plane *plane;
+ unsigned int index;
+
+ if (!state->planes[i])
+ continue;
+
+ plane = to_rcar_plane(state->planes[i]);
+ plane_state = to_rcar_du_plane_state(state->plane_states[i]);
+
+ /* If the plane is being disabled we don't need to go through
+ * the full reallocation procedure. Just mark the hardware
+ * plane(s) as freed.
+ */
+ if (!plane_state->format) {
+ index = plane - plane->group->planes.planes;
+ group_freed_planes[plane->group->index] |= 1 << index;
+ plane_state->hwindex = -1;
+ continue;
+ }
+
+ /* If the plane needs to be reallocated mark it as such, and
+ * mark the hardware plane(s) as free.
+ */
+ if (rcar_du_plane_needs_realloc(plane, plane_state)) {
+ groups |= 1 << plane->group->index;
+ needs_realloc = true;
+
+ index = plane - plane->group->planes.planes;
+ group_freed_planes[plane->group->index] |= 1 << index;
+ plane_state->hwindex = -1;
+ }
+ }
+
+ if (!needs_realloc)
+ return 0;
+
+ /* Grab all plane states for the groups that need reallocation to ensure
+ * locking and avoid racy updates. This serializes the update operation,
+ * but there's not much we can do about it as that's the hardware
+ * design.
+ *
+ * Compute the used planes mask for each group at the same time to avoid
+ * looping over the planes separately later.
+ */
+ while (groups) {
+ unsigned int index = ffs(groups) - 1;
+ struct rcar_du_group *group = &rcdu->groups[index];
+ unsigned int used_planes = 0;
+
+ for (i = 0; i < RCAR_DU_NUM_KMS_PLANES; ++i) {
+ struct rcar_du_plane *plane = &group->planes.planes[i];
+ struct rcar_du_plane_state *plane_state;
+ struct drm_plane_state *s;
+
+ s = drm_atomic_get_plane_state(state, &plane->plane);
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+
+ /* If the plane has been freed in the above loop its
+ * hardware planes must not be added to the used planes
+ * bitmask. However, the current state doesn't reflect
+ * the free state yet, as we've modified the new state
+ * above. Use the local freed planes list to check for
+ * that condition instead.
+ */
+ if (group_freed_planes[index] & (1 << i))
+ continue;
+
+ plane_state = to_rcar_du_plane_state(plane->plane.state);
+ used_planes |= rcar_du_plane_hwmask(plane_state);
+ }
+
+ group_free_planes[index] = 0xff & ~used_planes;
+ groups &= ~(1 << index);
+ }
+
+ /* Reallocate hardware planes for each plane that needs it. */
+ for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
+ struct rcar_du_plane_state *plane_state;
+ struct rcar_du_plane *plane;
+ int idx;
+
+ if (!state->planes[i])
+ continue;
+
+ plane = to_rcar_plane(state->planes[i]);
+ plane_state = to_rcar_du_plane_state(state->plane_states[i]);
+
+ /* Skip planes that are being disabled or don't need to be
+ * reallocated.
+ */
+ if (!plane_state->format ||
+ !rcar_du_plane_needs_realloc(plane, plane_state))
+ continue;
+
+ idx = rcar_du_plane_hwalloc(plane_state->format->planes,
+ group_free_planes[plane->group->index]);
+ if (idx < 0) {
+ dev_dbg(rcdu->dev, "%s: no available hardware plane\n",
+ __func__);
+ return idx;
+ }
+
+ plane_state->hwindex = idx;
+
+ group_free_planes[plane->group->index] &=
+ ~rcar_du_plane_hwmask(plane_state);
+ }
+
+ return 0;
+}
+
projects / linux.git / commitdiff