drm: atmel-hlcdc: add discard area support

The HLCDC IP provides a way to discard a specific area on the primary
plane (in case at least one of the overlay is activated and alpha
blending is disabled).
Doing this will reduce the amount of data to transfer from the main
memory to the Display Controller, and thus alleviate the load on the
memory bus (since this link is quite limited on such hardware,
this kind of optimization is really important).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c

@@ -212,7 +212,7 @@ static int atmel_hlcdc_crtc_atomic_check(struct drm_crtc *c,
 	if (atmel_hlcdc_dc_mode_valid(crtc->dc, &s->adjusted_mode) != MODE_OK)
 		return -EINVAL;
 
-	return 0;
+	return atmel_hlcdc_plane_prepare_disc_area(s);
 }
 
 static void atmel_hlcdc_crtc_atomic_begin(struct drm_crtc *c)

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.h

@@ -148,6 +148,8 @@ int atmel_hlcdc_dc_mode_valid(struct atmel_hlcdc_dc *dc,
 struct atmel_hlcdc_planes *
 atmel_hlcdc_create_planes(struct drm_device *dev);
 
+int atmel_hlcdc_plane_prepare_disc_area(struct drm_crtc_state *c_state);
+
 void atmel_hlcdc_crtc_irq(struct drm_crtc *c);
 
 void atmel_hlcdc_crtc_cancel_page_flip(struct drm_crtc *crtc,

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c

@@ -51,6 +51,13 @@ struct atmel_hlcdc_plane_state {
 
 	u8 alpha;
 
+	bool disc_updated;
+
+	int disc_x;
+	int disc_y;
+	int disc_w;
+	int disc_h;
+
 	/* These fields are private and should not be touched */
 	int bpp[ATMEL_HLCDC_MAX_PLANES];
 	unsigned int offsets[ATMEL_HLCDC_MAX_PLANES];
@@ -428,6 +435,104 @@ static void atmel_hlcdc_plane_update_buffers(struct atmel_hlcdc_plane *plane,
 	}
 }
 
+int
+atmel_hlcdc_plane_prepare_disc_area(struct drm_crtc_state *c_state)
+{
+	int disc_x = 0, disc_y = 0, disc_w = 0, disc_h = 0;
+	const struct atmel_hlcdc_layer_cfg_layout *layout;
+	struct atmel_hlcdc_plane_state *primary_state;
+	struct drm_plane_state *primary_s;
+	struct atmel_hlcdc_plane *primary;
+	struct drm_plane *ovl;
+
+	primary = drm_plane_to_atmel_hlcdc_plane(c_state->crtc->primary);
+	layout = &primary->layer.desc->layout;
+	if (!layout->disc_pos || !layout->disc_size)
+		return 0;
+
+	primary_s = drm_atomic_get_plane_state(c_state->state,
+					       &primary->base);
+	if (IS_ERR(primary_s))
+		return PTR_ERR(primary_s);
+
+	primary_state = drm_plane_state_to_atmel_hlcdc_plane_state(primary_s);
+
+	drm_atomic_crtc_state_for_each_plane(ovl, c_state) {
+		struct atmel_hlcdc_plane_state *ovl_state;
+		struct drm_plane_state *ovl_s;
+
+		if (ovl == c_state->crtc->primary)
+			continue;
+
+		ovl_s = drm_atomic_get_plane_state(c_state->state, ovl);
+		if (IS_ERR(ovl_s))
+			return PTR_ERR(ovl_s);
+
+		ovl_state = drm_plane_state_to_atmel_hlcdc_plane_state(ovl_s);
+
+		if (!ovl_s->fb ||
+		    atmel_hlcdc_format_embeds_alpha(ovl_s->fb->pixel_format) ||
+		    ovl_state->alpha != 255)
+			continue;
+
+		/* TODO: implement a smarter hidden area detection */
+		if (ovl_state->crtc_h * ovl_state->crtc_w < disc_h * disc_w)
+			continue;
+
+		disc_x = ovl_state->crtc_x;
+		disc_y = ovl_state->crtc_y;
+		disc_h = ovl_state->crtc_h;
+		disc_w = ovl_state->crtc_w;
+	}
+
+	if (disc_x == primary_state->disc_x &&
+	    disc_y == primary_state->disc_y &&
+	    disc_w == primary_state->disc_w &&
+	    disc_h == primary_state->disc_h)
+		return 0;
+
+
+	primary_state->disc_x = disc_x;
+	primary_state->disc_y = disc_y;
+	primary_state->disc_w = disc_w;
+	primary_state->disc_h = disc_h;
+	primary_state->disc_updated = true;
+
+	return 0;
+}
+
+static void
+atmel_hlcdc_plane_update_disc_area(struct atmel_hlcdc_plane *plane,
+				   struct atmel_hlcdc_plane_state *state)
+{
+	const struct atmel_hlcdc_layer_cfg_layout *layout =
+						&plane->layer.desc->layout;
+	int disc_surface = 0;
+
+	if (!state->disc_updated)
+		return;
+
+	disc_surface = state->disc_h * state->disc_w;
+
+	atmel_hlcdc_layer_update_cfg(&plane->layer, layout->general_config,
+				ATMEL_HLCDC_LAYER_DISCEN,
+				disc_surface ? ATMEL_HLCDC_LAYER_DISCEN : 0);
+
+	if (!disc_surface)
+		return;
+
+	atmel_hlcdc_layer_update_cfg(&plane->layer,
+				     layout->disc_pos,
+				     0xffffffff,
+				     state->disc_x | (state->disc_y << 16));
+
+	atmel_hlcdc_layer_update_cfg(&plane->layer,
+				     layout->disc_size,
+				     0xffffffff,
+				     (state->disc_w - 1) |
+				     ((state->disc_h - 1) << 16));
+}
+
 static int atmel_hlcdc_plane_atomic_check(struct drm_plane *p,
 					  struct drm_plane_state *s)
 {
@@ -628,6 +733,7 @@ static void atmel_hlcdc_plane_atomic_update(struct drm_plane *p,
 	atmel_hlcdc_plane_update_general_settings(plane, state);
 	atmel_hlcdc_plane_update_format(plane, state);
 	atmel_hlcdc_plane_update_buffers(plane, state);
+	atmel_hlcdc_plane_update_disc_area(plane, state);
 
 	atmel_hlcdc_layer_update_commit(&plane->layer);
 }
@@ -773,6 +879,8 @@ atmel_hlcdc_plane_atomic_duplicate_state(struct drm_plane *p)
 	if (!copy)
 		return NULL;
 
+	copy->disc_updated = false;
+
 	if (copy->base.fb)
 		drm_framebuffer_reference(copy->base.fb);