drm/tegra: dc: Implement legacy blending

This implements alpha blending on legacy display controllers (Tegra20,
Tegra30 and Tegra114). While it's theoretically possible to support the
zpos property to enable userspace to specify the Z-order of each plane
individually, this is not currently supported and the same fixed Z-
order as previously defined is used.

Reverts commit 71835caa00 ("drm/tegra: fb: Force alpha formats") since
the opaque formats are now supported.

Reported-by: Dmitry Osipenko <digetx@gmail.com>
Fixes: 7772fdaef9 ("drm/tegra: Support ARGB and ABGR formats")
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -154,30 +154,53 @@ static inline u32 compute_initial_dda(unsigned int in)
 
 static void tegra_plane_setup_blending_legacy(struct tegra_plane *plane)
 {
+	u32 background[3] = {
+		BLEND_WEIGHT1(0) | BLEND_WEIGHT0(0) | BLEND_COLOR_KEY_NONE,
+		BLEND_WEIGHT1(0) | BLEND_WEIGHT0(0) | BLEND_COLOR_KEY_NONE,
+		BLEND_WEIGHT1(0) | BLEND_WEIGHT0(0) | BLEND_COLOR_KEY_NONE,
+	};
+	u32 foreground = BLEND_WEIGHT1(255) | BLEND_WEIGHT0(255) |
+			 BLEND_COLOR_KEY_NONE;
+	u32 blendnokey = BLEND_WEIGHT1(255) | BLEND_WEIGHT0(255);
+	struct tegra_plane_state *state;
+	unsigned int i;
+
+	state = to_tegra_plane_state(plane->base.state);
+
+	/* alpha contribution is 1 minus sum of overlapping windows */
+	for (i = 0; i < 3; i++) {
+		if (state->dependent[i])
+			background[i] |= BLEND_CONTROL_DEPENDENT;
+	}
+
+	/* enable alpha blending if pixel format has an alpha component */
+	if (!state->opaque)
+		foreground |= BLEND_CONTROL_ALPHA;
+
 	/*
 	 * Disable blending and assume Window A is the bottom-most window,
 	 * Window C is the top-most window and Window B is in the middle.
 	 */
-	tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_NOKEY);
-	tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_1WIN);
+	tegra_plane_writel(plane, blendnokey, DC_WIN_BLEND_NOKEY);
+	tegra_plane_writel(plane, foreground, DC_WIN_BLEND_1WIN);
 
 	switch (plane->index) {
 	case 0:
-		tegra_plane_writel(plane, 0x000000, DC_WIN_BLEND_2WIN_X);
-		tegra_plane_writel(plane, 0x000000, DC_WIN_BLEND_2WIN_Y);
-		tegra_plane_writel(plane, 0x000000, DC_WIN_BLEND_3WIN_XY);
+		tegra_plane_writel(plane, background[0], DC_WIN_BLEND_2WIN_X);
+		tegra_plane_writel(plane, background[1], DC_WIN_BLEND_2WIN_Y);
+		tegra_plane_writel(plane, background[2], DC_WIN_BLEND_3WIN_XY);
 		break;
 
 	case 1:
-		tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_2WIN_X);
-		tegra_plane_writel(plane, 0x000000, DC_WIN_BLEND_2WIN_Y);
-		tegra_plane_writel(plane, 0x000000, DC_WIN_BLEND_3WIN_XY);
+		tegra_plane_writel(plane, foreground, DC_WIN_BLEND_2WIN_X);
+		tegra_plane_writel(plane, background[1], DC_WIN_BLEND_2WIN_Y);
+		tegra_plane_writel(plane, background[2], DC_WIN_BLEND_3WIN_XY);
 		break;
 
 	case 2:
-		tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_2WIN_X);
-		tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_2WIN_Y);
-		tegra_plane_writel(plane, 0xffff00, DC_WIN_BLEND_3WIN_XY);
+		tegra_plane_writel(plane, foreground, DC_WIN_BLEND_2WIN_X);
+		tegra_plane_writel(plane, foreground, DC_WIN_BLEND_2WIN_Y);
+		tegra_plane_writel(plane, foreground, DC_WIN_BLEND_3WIN_XY);
 		break;
 	}
 }
@@ -353,6 +376,11 @@ static const u32 tegra20_primary_formats[] = {
 	DRM_FORMAT_RGBA5551,
 	DRM_FORMAT_ABGR8888,
 	DRM_FORMAT_ARGB8888,
+	/* non-native formats */
+	DRM_FORMAT_XRGB1555,
+	DRM_FORMAT_RGBX5551,
+	DRM_FORMAT_XBGR8888,
+	DRM_FORMAT_XRGB8888,
 };
 
 static const u32 tegra114_primary_formats[] = {
@@ -409,18 +437,40 @@ static int tegra_plane_atomic_check(struct drm_plane *plane,
 	struct tegra_bo_tiling *tiling = &plane_state->tiling;
 	struct tegra_plane *tegra = to_tegra_plane(plane);
 	struct tegra_dc *dc = to_tegra_dc(state->crtc);
+	unsigned int format;
 	int err;
 
 	/* no need for further checks if the plane is being disabled */
 	if (!state->crtc)
 		return 0;
 
-	err = tegra_plane_format(state->fb->format->format,
-				 &plane_state->format,
+	err = tegra_plane_format(state->fb->format->format, &format,
 				 &plane_state->swap);
 	if (err < 0)
 		return err;
 
+	/*
+	 * Tegra20 and Tegra30 are special cases here because they support
+	 * only variants of specific formats with an alpha component, but not
+	 * the corresponding opaque formats. However, the opaque formats can
+	 * be emulated by disabling alpha blending for the plane.
+	 */
+	if (!dc->soc->supports_blending) {
+		if (!tegra_plane_format_has_alpha(format)) {
+			err = tegra_plane_format_get_alpha(format, &format);
+			if (err < 0)
+				return err;
+
+			plane_state->opaque = true;
+		} else {
+			plane_state->opaque = false;
+		}
+
+		tegra_plane_check_dependent(tegra, plane_state);
+	}
+
+	plane_state->format = format;
+
 	err = tegra_fb_get_tiling(state->fb, tiling);
 	if (err < 0)
 		return err;
@@ -737,6 +787,11 @@ static const u32 tegra20_overlay_formats[] = {
 	DRM_FORMAT_RGBA5551,
 	DRM_FORMAT_ABGR8888,
 	DRM_FORMAT_ARGB8888,
+	/* non-native formats */
+	DRM_FORMAT_XRGB1555,
+	DRM_FORMAT_RGBX5551,
+	DRM_FORMAT_XBGR8888,
+	DRM_FORMAT_XRGB8888,
 	/* planar formats */
 	DRM_FORMAT_UYVY,
 	DRM_FORMAT_YUYV,

drivers/gpu/drm/tegra/dc.h

@@ -649,8 +649,20 @@ int tegra_dc_rgb_exit(struct tegra_dc *dc);
 #define DC_WIN_DV_CONTROL			0x70e
 
 #define DC_WIN_BLEND_NOKEY			0x70f
+#define  BLEND_WEIGHT1(x) (((x) & 0xff) << 16)
+#define  BLEND_WEIGHT0(x) (((x) & 0xff) <<  8)
+
 #define DC_WIN_BLEND_1WIN			0x710
+#define  BLEND_CONTROL_FIX    (0 << 2)
+#define  BLEND_CONTROL_ALPHA  (1 << 2)
+#define  BLEND_COLOR_KEY_NONE (0 << 0)
+#define  BLEND_COLOR_KEY_0    (1 << 0)
+#define  BLEND_COLOR_KEY_1    (2 << 0)
+#define  BLEND_COLOR_KEY_BOTH (3 << 0)
+
 #define DC_WIN_BLEND_2WIN_X			0x711
+#define  BLEND_CONTROL_DEPENDENT (2 << 2)
+
 #define DC_WIN_BLEND_2WIN_Y			0x712
 #define DC_WIN_BLEND_3WIN_XY			0x713
 

drivers/gpu/drm/tegra/fb.c

@@ -254,18 +254,6 @@ static int tegra_fbdev_probe(struct drm_fb_helper *helper,
 	cmd.pitches[0] = round_up(sizes->surface_width * bytes_per_pixel,
 				  tegra->pitch_align);
 
-	/*
-	 * Early generations of Tegra (Tegra20 and Tegra30) do not support any
-	 * of the X* or *X formats, only their A* or *A equivalents. Force the
-	 * legacy framebuffer format to include an alpha component so that the
-	 * framebuffer emulation can be supported on all generations.
-	 */
-	if (sizes->surface_bpp == 32 && sizes->surface_depth == 24)
-		sizes->surface_depth = 32;
-
-	if (sizes->surface_bpp == 16 && sizes->surface_depth == 15)
-		sizes->surface_depth = 16;
-
 	cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
 						     sizes->surface_depth);
 

drivers/gpu/drm/tegra/plane.c

@@ -43,6 +43,7 @@ tegra_plane_atomic_duplicate_state(struct drm_plane *plane)
 {
 	struct tegra_plane_state *state = to_tegra_plane_state(plane->state);
 	struct tegra_plane_state *copy;
+	unsigned int i;
 
 	copy = kmalloc(sizeof(*copy), GFP_KERNEL);
 	if (!copy)
@@ -52,6 +53,10 @@ tegra_plane_atomic_duplicate_state(struct drm_plane *plane)
 	copy->tiling = state->tiling;
 	copy->format = state->format;
 	copy->swap = state->swap;
+	copy->opaque = state->opaque;
+
+	for (i = 0; i < 3; i++)
+		copy->dependent[i] = state->dependent[i];
 
 	return &copy->base;
 }
@@ -238,3 +243,136 @@ bool tegra_plane_format_is_yuv(unsigned int format, bool *planar)
 
 	return false;
 }
+
+static bool __drm_format_has_alpha(u32 format)
+{
+	switch (format) {
+	case DRM_FORMAT_ARGB1555:
+	case DRM_FORMAT_RGBA5551:
+	case DRM_FORMAT_ABGR8888:
+	case DRM_FORMAT_ARGB8888:
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * This is applicable to Tegra20 and Tegra30 only where the opaque formats can
+ * be emulated using the alpha formats and alpha blending disabled.
+ */
+bool tegra_plane_format_has_alpha(unsigned int format)
+{
+	switch (format) {
+	case WIN_COLOR_DEPTH_B5G5R5A1:
+	case WIN_COLOR_DEPTH_A1B5G5R5:
+	case WIN_COLOR_DEPTH_R8G8B8A8:
+	case WIN_COLOR_DEPTH_B8G8R8A8:
+		return true;
+	}
+
+	return false;
+}
+
+int tegra_plane_format_get_alpha(unsigned int opaque, unsigned int *alpha)
+{
+	switch (opaque) {
+	case WIN_COLOR_DEPTH_B5G5R5X1:
+		*alpha = WIN_COLOR_DEPTH_B5G5R5A1;
+		return 0;
+
+	case WIN_COLOR_DEPTH_X1B5G5R5:
+		*alpha = WIN_COLOR_DEPTH_A1B5G5R5;
+		return 0;
+
+	case WIN_COLOR_DEPTH_R8G8B8X8:
+		*alpha = WIN_COLOR_DEPTH_R8G8B8A8;
+		return 0;
+
+	case WIN_COLOR_DEPTH_B8G8R8X8:
+		*alpha = WIN_COLOR_DEPTH_B8G8R8A8;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+unsigned int tegra_plane_get_overlap_index(struct tegra_plane *plane,
+					   struct tegra_plane *other)
+{
+	unsigned int index = 0, i;
+
+	WARN_ON(plane == other);
+
+	for (i = 0; i < 3; i++) {
+		if (i == plane->index)
+			continue;
+
+		if (i == other->index)
+			break;
+
+		index++;
+	}
+
+	return index;
+}
+
+void tegra_plane_check_dependent(struct tegra_plane *tegra,
+				 struct tegra_plane_state *state)
+{
+	struct drm_plane_state *old, *new;
+	struct drm_plane *plane;
+	unsigned int zpos[2];
+	unsigned int i;
+
+	for (i = 0; i < 3; i++)
+		state->dependent[i] = false;
+
+	for (i = 0; i < 2; i++)
+		zpos[i] = 0;
+
+	for_each_oldnew_plane_in_state(state->base.state, plane, old, new, i) {
+		struct tegra_plane *p = to_tegra_plane(plane);
+		unsigned index;
+
+		/* skip this plane and planes on different CRTCs */
+		if (p == tegra || new->crtc != state->base.crtc)
+			continue;
+
+		index = tegra_plane_get_overlap_index(tegra, p);
+
+		/*
+		 * If any of the other planes is on top of this plane and uses
+		 * a format with an alpha component, mark this plane as being
+		 * dependent, meaning it's alpha value will be 1 minus the sum
+		 * of alpha components of the overlapping planes.
+		 */
+		if (p->index > tegra->index) {
+			if (__drm_format_has_alpha(new->fb->format->format))
+				state->dependent[index] = true;
+
+			/* keep track of the Z position */
+			zpos[index] = p->index;
+		}
+	}
+
+	/*
+	 * The region where three windows overlap is the intersection of the
+	 * two regions where two windows overlap. It contributes to the area
+	 * if any of the windows on top of it have an alpha component.
+	 */
+	for (i = 0; i < 2; i++)
+		state->dependent[2] = state->dependent[2] ||
+				      state->dependent[i];
+
+	/*
+	 * However, if any of the windows on top of this window is opaque, it
+	 * will completely conceal this window within that area, so avoid the
+	 * window from contributing to the area.
+	 */
+	for (i = 0; i < 2; i++) {
+		if (zpos[i] > tegra->index)
+			state->dependent[2] = state->dependent[2] &&
+					      state->dependent[i];
+	}
+}

drivers/gpu/drm/tegra/plane.h

@@ -40,6 +40,10 @@ struct tegra_plane_state {
 	struct tegra_bo_tiling tiling;
 	u32 format;
 	u32 swap;
+
+	/* used for legacy blending support only */
+	bool opaque;
+	bool dependent[3];
 };
 
 static inline struct tegra_plane_state *
@@ -58,5 +62,9 @@ int tegra_plane_state_add(struct tegra_plane *plane,
 
 int tegra_plane_format(u32 fourcc, u32 *format, u32 *swap);
 bool tegra_plane_format_is_yuv(unsigned int format, bool *planar);
+bool tegra_plane_format_has_alpha(unsigned int format);
+int tegra_plane_format_get_alpha(unsigned int opaque, unsigned int *alpha);
+void tegra_plane_check_dependent(struct tegra_plane *tegra,
+				 struct tegra_plane_state *state);
 
 #endif /* TEGRA_PLANE_H */