drm/apple: Update swap handling

- opaque -> is_premultiplied
- swap_enabled BIT(31) seems to be update background with
  dcp_swap.bg_color
- add unused fields is_tearing_allowed, ycbcr_matrix, protection_opts,
  unk_num, unk_denom

Changes: use is_premultiplied only for XRGB8/XBGR8, Update background
only when necessary.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/apple/iomfb.c

@@ -1062,9 +1062,9 @@ void dcp_poweroff(struct platform_device *pdev)
 	// clear surfaces
 	memset(&dcp->swap, 0, sizeof(dcp->swap));
 
-	dcp->swap.swap.swap_enabled = DCP_REMOVE_LAYERS | 0x7;
-	dcp->swap.swap.swap_completed = DCP_REMOVE_LAYERS | 0x7;
-	dcp->swap.swap.unk_10c = 0xFF000000;
+	dcp->swap.swap.swap_enabled =
+		dcp->swap.swap.swap_completed = IOMFB_SET_BACKGROUND | 0xF;
+	dcp->swap.swap.bg_color = 0xFF000000;
 
 	/*
 	 * Turn off the backlight. This matters because the DCP's idea of
@@ -1618,7 +1618,8 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 	 * sticks around.
 	 */
 	if (!dcp->surfaces_cleared) {
-		req->swap.swap_enabled = DCP_REMOVE_LAYERS | 0xF;
+		req->swap.swap_enabled = IOMFB_SET_BACKGROUND | 0xF;
+		req->swap.bg_color = 0xFF000000;
 		dcp->surfaces_cleared = true;
 	}
 
@@ -1628,7 +1629,7 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 		struct drm_framebuffer *fb = new_state->fb;
 		struct drm_gem_dma_object *obj;
 		struct drm_rect src_rect;
-		bool opaque = false;
+		bool is_premultiplied = false;
 
 		/* skip planes not for this crtc */
 		if (old_state->crtc != crtc && new_state->crtc != crtc)
@@ -1659,18 +1660,21 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 		}
 
 		if (!new_state->fb) {
-			if (old_state->fb)
-				req->swap.swap_enabled |= DCP_REMOVE_LAYERS;
-
 			l += 1;
 			continue;
 		}
 		req->surf_null[l] = false;
 		has_surface = 1;
 
-		if (!fb->format->has_alpha ||
-		    new_state->plane->type == DRM_PLANE_TYPE_PRIMARY)
-		    opaque = true;
+		/*
+		 * DCP doesn't support XBGR8 / XRGB8 natively. Blending as
+		 * pre-multiplied alpha with a black background can be used as
+		 * workaround for the bottommost plane.
+		 */
+		if (fb->format->format == DRM_FORMAT_XRGB8888 ||
+		    fb->format->format == DRM_FORMAT_XBGR8888)
+		    is_premultiplied = true;
+
 		drm_rect_fp_to_int(&src_rect, &new_state->src);
 
 		req->swap.src_rect[l] = drm_to_dcp_rect(&src_rect);
@@ -1688,7 +1692,7 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 			req->surf_iova[l] = obj->dma_addr + fb->offsets[0];
 
 		req->surf[l] = (struct dcp_surface){
-			.opaque = opaque,
+			.is_premultiplied = is_premultiplied,
 			.format = drm_format_to_dcp(fb->format->format),
 			.xfer_func = DCP_XFER_FUNC_SDR,
 			.colorspace = DCP_COLORSPACE_NATIVE,
@@ -1709,9 +1713,6 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 		l += 1;
 	}
 
-	/* These fields should be set together */
-	req->swap.swap_completed = req->swap.swap_enabled;
-
 	if (modeset) {
 		struct dcp_display_mode *mode;
 		struct dcp_wait_cookie *cookie;
@@ -1772,9 +1773,15 @@ void dcp_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 			return;
 		}
 
+		/* Set black background */
+		req->swap.swap_enabled |= IOMFB_SET_BACKGROUND;
+		req->swap.bg_color = 0xFF000000;
 		req->clear = 1;
 	}
 
+	/* These fields should be set together */
+	req->swap.swap_completed = req->swap.swap_enabled;
+
 	/* update brightness if changed */
 	if (dcp->brightness.update) {
 		req->swap.bl_unk = 1;

drivers/gpu/drm/apple/iomfb.h

@@ -102,12 +102,9 @@ struct dcp_rect {
 } __packed;
 
 /*
- * Set in the swap_{enabled,completed} field to remove missing
- * layers. Without this flag, the DCP will assume missing layers have
- * not changed since the previous frame and will preserve their
- * content.
-  */
-#define DCP_REMOVE_LAYERS BIT(31)
+ * Update background color to struct dcp_swap.bg_color
+ */
+#define IOMFB_SET_BACKGROUND	BIT(31)
 
 struct dcp_swap {
 	u64 ts1;
@@ -126,7 +123,7 @@ struct dcp_swap {
 	u32 swap_enabled;
 	u32 swap_completed;
 
-	u32 unk_10c;
+	u32 bg_color;
 	u8 unk_110[0x1b8];
 	u32 unk_2c8;
 	u8 unk_2cc[0x14];
@@ -160,12 +157,12 @@ struct dcp_component_types {
 /* Information describing a surface */
 struct dcp_surface {
 	u8 is_tiled;
-	u8 unk_1;
-	u8 opaque; /** ignore alpha, also required YUV overlays */
+	u8 is_tearing_allowed;
+	u8 is_premultiplied;
 	u32 plane_cnt;
 	u32 plane_cnt2;
 	u32 format; /* DCP fourcc */
-	u32 unk_f;
+	u32 ycbcr_matrix;
 	u8 xfer_func;
 	u8 colorspace;
 	u32 stride;
@@ -176,16 +173,16 @@ struct dcp_surface {
 	u32 width;
 	u32 height;
 	u32 buf_size;
-	u32 unk_2d;
-	u32 unk_31;
+	u64 protection_opts;
 	u32 surface_id;
 	struct dcp_component_types comp_types[MAX_PLANES];
 	u64 has_comp;
 	struct dcp_plane_info planes[MAX_PLANES];
 	u64 has_planes;
 	u32 compression_info[MAX_PLANES][13];
 	u64 has_compr_info;
-	u64 unk_1f5;
+	u32 unk_num;
+	u32 unk_denom;
 	u8 padding[7];
 } __packed;