1 files changed, 541 insertions, 170 deletions

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index e49523866e1d..3cf3f26e0d8e 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -4,210 +4,583 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_blend.h>
 #include <drm/drm_fourcc.h>
+#include <drm/drm_fixed.h>
 #include <drm/drm_gem_framebuffer_helper.h>
-#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_print.h>
 #include <drm/drm_vblank.h>
+#include <linux/minmax.h>
+#include <kunit/visibility.h>
 
-#include "vkms_drv.h"
+#include "vkms_composer.h"
+#include "vkms_luts.h"
 
-static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
-				 const struct vkms_composer *composer)
+static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
 {
-	u32 pixel;
-	int src_offset = composer->offset + (y * composer->pitch)
-				      + (x * composer->cpp);
+	u32 new_color;
 
-	pixel = *(u32 *)&buffer[src_offset];
+	new_color = (src * 0xffff + dst * (0xffff - alpha));
 
-	return pixel;
+	return DIV_ROUND_CLOSEST(new_color, 0xffff);
 }
 
 /**
- * compute_crc - Compute CRC value on output frame
+ * pre_mul_alpha_blend - alpha blending equation
+ * @stage_buffer: The line with the pixels from src_plane
+ * @output_buffer: A line buffer that receives all the blends output
+ * @x_start: The start offset
+ * @pixel_count: The number of pixels to blend
  *
- * @vaddr: address to final framebuffer
- * @composer: framebuffer's metadata
+ * The pixels [@x_start;@x_start+@pixel_count) in stage_buffer are blended at
+ * [@x_start;@x_start+@pixel_count) in output_buffer.
  *
- * returns CRC value computed using crc32 on the visible portion of
- * the final framebuffer at vaddr_out
+ * The current DRM assumption is that pixel color values have been already
+ * pre-multiplied with the alpha channel values. See more
+ * drm_plane_create_blend_mode_property(). Also, this formula assumes a
+ * completely opaque background.
  */
-static uint32_t compute_crc(const u8 *vaddr,
-			    const struct vkms_composer *composer)
+static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
+				struct line_buffer *output_buffer, int x_start, int pixel_count)
 {
-	int x, y;
-	u32 crc = 0, pixel = 0;
-	int x_src = composer->src.x1 >> 16;
-	int y_src = composer->src.y1 >> 16;
-	int h_src = drm_rect_height(&composer->src) >> 16;
-	int w_src = drm_rect_width(&composer->src) >> 16;
-
-	for (y = y_src; y < y_src + h_src; ++y) {
-		for (x = x_src; x < x_src + w_src; ++x) {
-			pixel = get_pixel_from_buffer(x, y, vaddr, composer);
-			crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
-		}
+	struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
+	const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];
+
+	for (int i = 0; i < pixel_count; i++) {
+		out[i].a = (u16)0xffff;
+		out[i].r = pre_mul_blend_channel(in[i].r, out[i].r, in[i].a);
+		out[i].g = pre_mul_blend_channel(in[i].g, out[i].g, in[i].a);
+		out[i].b = pre_mul_blend_channel(in[i].b, out[i].b, in[i].a);
 	}
+}
 
-	return crc;
+
+static void fill_background(const struct pixel_argb_u16 *background_color,
+			    struct line_buffer *output_buffer)
+{
+	for (size_t i = 0; i < output_buffer->n_pixels; i++)
+		output_buffer->pixels[i] = *background_color;
 }
 
-static u8 blend_channel(u8 src, u8 dst, u8 alpha)
+// lerp(a, b, t) = a + (b - a) * t
+VISIBLE_IF_KUNIT u16 lerp_u16(u16 a, u16 b, s64 t)
 {
-	u32 pre_blend;
-	u8 new_color;
+	s64 a_fp = drm_int2fixp(a);
+	s64 b_fp = drm_int2fixp(b);
 
-	pre_blend = (src * 255 + dst * (255 - alpha));
+	s64 delta = drm_fixp_mul(b_fp - a_fp, t);
 
-	/* Faster div by 255 */
-	new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8);
+	return drm_fixp2int_round(a_fp + delta);
+}
+EXPORT_SYMBOL_IF_KUNIT(lerp_u16);
+
+VISIBLE_IF_KUNIT s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
+{
+	s64 color_channel_fp = drm_int2fixp(channel_value);
 
-	return new_color;
+	return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
 }
+EXPORT_SYMBOL_IF_KUNIT(get_lut_index);
 
-/**
- * alpha_blend - alpha blending equation
- * @argb_src: src pixel on premultiplied alpha mode
- * @argb_dst: dst pixel completely opaque
- *
- * blend pixels using premultiplied blend formula. The current DRM assumption
- * is that pixel color values have been already pre-multiplied with the alpha
- * channel values. See more drm_plane_create_blend_mode_property(). Also, this
- * formula assumes a completely opaque background.
- */
-static void alpha_blend(const u8 *argb_src, u8 *argb_dst)
+VISIBLE_IF_KUNIT u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
+						enum lut_channel channel)
+{
+	s64 lut_index = get_lut_index(lut, channel_value);
+	u16 *floor_lut_value, *ceil_lut_value;
+	u16 floor_channel_value, ceil_channel_value;
+
+	/*
+	 * This checks if `struct drm_color_lut` has any gap added by the compiler
+	 * between the struct fields.
+	 */
+	static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
+
+	floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
+	if (drm_fixp2int(lut_index) == (lut->lut_length - 1))
+		/* We're at the end of the LUT array, use same value for ceil and floor */
+		ceil_lut_value = floor_lut_value;
+	else
+		ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
+
+	floor_channel_value = floor_lut_value[channel];
+	ceil_channel_value = ceil_lut_value[channel];
+
+	return lerp_u16(floor_channel_value, ceil_channel_value,
+			lut_index & DRM_FIXED_DECIMAL_MASK);
+}
+EXPORT_SYMBOL_IF_KUNIT(apply_lut_to_channel_value);
+
+
+static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
+{
+	if (!crtc_state->gamma_lut.base)
+		return;
+
+	if (!crtc_state->gamma_lut.lut_length)
+		return;
+
+	for (size_t x = 0; x < output_buffer->n_pixels; x++) {
+		struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];
+
+		pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
+		pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
+		pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
+	}
+}
+
+VISIBLE_IF_KUNIT void apply_3x4_matrix(struct pixel_argb_s32 *pixel,
+				       const struct drm_color_ctm_3x4 *matrix)
+{
+	s64 rf, gf, bf;
+	s64 r, g, b;
+
+	r = drm_int2fixp(pixel->r);
+	g = drm_int2fixp(pixel->g);
+	b = drm_int2fixp(pixel->b);
+
+	rf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[0]), r) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[1]), g) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[2]), b) +
+	     drm_sm2fixp(matrix->matrix[3]);
+
+	gf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[4]), r) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[5]), g) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[6]), b) +
+	     drm_sm2fixp(matrix->matrix[7]);
+
+	bf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[8]), r) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[9]), g) +
+	     drm_fixp_mul(drm_sm2fixp(matrix->matrix[10]), b) +
+	     drm_sm2fixp(matrix->matrix[11]);
+
+	pixel->r = drm_fixp2int_round(rf);
+	pixel->g = drm_fixp2int_round(gf);
+	pixel->b = drm_fixp2int_round(bf);
+}
+EXPORT_SYMBOL_IF_KUNIT(apply_3x4_matrix);
+
+static void apply_colorop(struct pixel_argb_s32 *pixel, struct drm_colorop *colorop)
 {
-	u8 alpha;
+	struct drm_colorop_state *colorop_state = colorop->state;
+	struct drm_device *dev = colorop->dev;
+
+	if (colorop->type == DRM_COLOROP_1D_CURVE) {
+		switch (colorop_state->curve_1d_type) {
+		case DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF:
+			pixel->r = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->r, LUT_RED);
+			pixel->g = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->g, LUT_GREEN);
+			pixel->b = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->b, LUT_BLUE);
+			break;
+		case DRM_COLOROP_1D_CURVE_SRGB_EOTF:
+			pixel->r = apply_lut_to_channel_value(&srgb_eotf, pixel->r, LUT_RED);
+			pixel->g = apply_lut_to_channel_value(&srgb_eotf, pixel->g, LUT_GREEN);
+			pixel->b = apply_lut_to_channel_value(&srgb_eotf, pixel->b, LUT_BLUE);
+			break;
+		default:
+			drm_WARN_ONCE(dev, true,
+				      "unknown colorop 1D curve type %d\n",
+				      colorop_state->curve_1d_type);
+			break;
+		}
+	} else if (colorop->type == DRM_COLOROP_CTM_3X4) {
+		if (colorop_state->data)
+			apply_3x4_matrix(pixel,
+					 (struct drm_color_ctm_3x4 *)colorop_state->data->data);
+	}
+}
 
-	alpha = argb_src[3];
-	argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], alpha);
-	argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], alpha);
-	argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], alpha);
+static void pre_blend_color_transform(const struct vkms_plane_state *plane_state,
+				      struct line_buffer *output_buffer)
+{
+	struct pixel_argb_s32 pixel;
+
+	for (size_t x = 0; x < output_buffer->n_pixels; x++) {
+		struct drm_colorop *colorop = plane_state->base.base.color_pipeline;
+
+		/*
+		 * Some operations, such as applying a BT709 encoding matrix,
+		 * followed by a decoding matrix, require that we preserve
+		 * values above 1.0 and below 0.0 until the end of the pipeline.
+		 *
+		 * Pack the 16-bit UNORM values into s32 to give us head-room to
+		 * avoid clipping until we're at the end of the pipeline. Clip
+		 * intentionally at the end of the pipeline before packing
+		 * UNORM values back into u16.
+		 */
+		pixel.a = output_buffer->pixels[x].a;
+		pixel.r = output_buffer->pixels[x].r;
+		pixel.g = output_buffer->pixels[x].g;
+		pixel.b = output_buffer->pixels[x].b;
+
+		while (colorop) {
+			struct drm_colorop_state *colorop_state;
+
+			colorop_state = colorop->state;
+
+			if (!colorop_state)
+				return;
+
+			if (!colorop_state->bypass)
+				apply_colorop(&pixel, colorop);
+
+			colorop = colorop->next;
+		}
+
+		/* clamp values */
+		output_buffer->pixels[x].a = clamp_val(pixel.a, 0, 0xffff);
+		output_buffer->pixels[x].r = clamp_val(pixel.r, 0, 0xffff);
+		output_buffer->pixels[x].g = clamp_val(pixel.g, 0, 0xffff);
+		output_buffer->pixels[x].b = clamp_val(pixel.b, 0, 0xffff);
+	}
 }
 
 /**
- * x_blend - blending equation that ignores the pixel alpha
+ * direction_for_rotation() - Get the correct reading direction for a given rotation
  *
- * overwrites RGB color value from src pixel to dst pixel.
+ * @rotation: Rotation to analyze. It correspond the field @frame_info.rotation.
+ *
+ * This function will use the @rotation setting of a source plane to compute the reading
+ * direction in this plane which correspond to a "left to right writing" in the CRTC.
+ * For example, if the buffer is reflected on X axis, the pixel must be read from right to left
+ * to be written from left to right on the CRTC.
  */
-static void x_blend(const u8 *xrgb_src, u8 *xrgb_dst)
+static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
 {
-	memcpy(xrgb_dst, xrgb_src, sizeof(u8) * 3);
+	struct drm_rect tmp_a, tmp_b;
+	int x, y;
+
+	/*
+	 * Points A and B are depicted as zero-size rectangles on the CRTC.
+	 * The CRTC writing direction is from A to B. The plane reading direction
+	 * is discovered by inverse-transforming A and B.
+	 * The reading direction is computed by rotating the vector AB (top-left to top-right) in a
+	 * 1x1 square.
+	 */
+
+	tmp_a = DRM_RECT_INIT(0, 0, 0, 0);
+	tmp_b = DRM_RECT_INIT(1, 0, 0, 0);
+	drm_rect_rotate_inv(&tmp_a, 1, 1, rotation);
+	drm_rect_rotate_inv(&tmp_b, 1, 1, rotation);
+
+	x = tmp_b.x1 - tmp_a.x1;
+	y = tmp_b.y1 - tmp_a.y1;
+
+	if (x == 1 && y == 0)
+		return READ_LEFT_TO_RIGHT;
+	else if (x == -1 && y == 0)
+		return READ_RIGHT_TO_LEFT;
+	else if (y == 1 && x == 0)
+		return READ_TOP_TO_BOTTOM;
+	else if (y == -1 && x == 0)
+		return READ_BOTTOM_TO_TOP;
+
+	WARN_ONCE(true, "The inverse of the rotation gives an incorrect direction.");
+	return READ_LEFT_TO_RIGHT;
 }
 
 /**
- * blend - blend value at vaddr_src with value at vaddr_dst
- * @vaddr_dst: destination address
- * @vaddr_src: source address
- * @dst_composer: destination framebuffer's metadata
- * @src_composer: source framebuffer's metadata
- * @pixel_blend: blending equation based on plane format
+ * clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend
+ * process.
  *
- * Blend the vaddr_src value with the vaddr_dst value using a pixel blend
- * equation according to the supported plane formats DRM_FORMAT_(A/XRGB8888)
- * and clearing alpha channel to an completely opaque background. This function
- * uses buffer's metadata to locate the new composite values at vaddr_dst.
+ * @direction: direction of the reading
+ * @current_plane: current plane blended
+ * @src_line: source line of the reading. Only the top-left coordinate is used. This rectangle
+ * must be rotated and have a shape of 1*pixel_count if @direction is vertical and a shape of
+ * pixel_count*1 if @direction is horizontal.
+ * @src_x_start: x start coordinate for the line reading
+ * @src_y_start: y start coordinate for the line reading
+ * @dst_x_start: x coordinate to blend the read line
+ * @pixel_count: number of pixels to blend
  *
- * TODO: completely clear the primary plane (a = 0xff) before starting to blend
- * pixel color values
+ * This function is mainly a safety net to avoid reading outside the source buffer. As the
+ * userspace should never ask to read outside the source plane, all the cases covered here should
+ * be dead code.
  */
-static void blend(void *vaddr_dst, void *vaddr_src,
-		  struct vkms_composer *dst_composer,
-		  struct vkms_composer *src_composer,
-		  void (*pixel_blend)(const u8 *, u8 *))
+static void clamp_line_coordinates(enum pixel_read_direction direction,
+				   const struct vkms_plane_state *current_plane,
+				   const struct drm_rect *src_line, int *src_x_start,
+				   int *src_y_start, int *dst_x_start, int *pixel_count)
 {
-	int i, j, j_dst, i_dst;
-	int offset_src, offset_dst;
-	u8 *pixel_dst, *pixel_src;
-
-	int x_src = src_composer->src.x1 >> 16;
-	int y_src = src_composer->src.y1 >> 16;
-
-	int x_dst = src_composer->dst.x1;
-	int y_dst = src_composer->dst.y1;
-	int h_dst = drm_rect_height(&src_composer->dst);
-	int w_dst = drm_rect_width(&src_composer->dst);
-
-	int y_limit = y_src + h_dst;
-	int x_limit = x_src + w_dst;
-
-	for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
-		for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
-			offset_dst = dst_composer->offset
-				     + (i_dst * dst_composer->pitch)
-				     + (j_dst++ * dst_composer->cpp);
-			offset_src = src_composer->offset
-				     + (i * src_composer->pitch)
-				     + (j * src_composer->cpp);
-
-			pixel_src = (u8 *)(vaddr_src + offset_src);
-			pixel_dst = (u8 *)(vaddr_dst + offset_dst);
-			pixel_blend(pixel_src, pixel_dst);
-			/* clearing alpha channel (0xff)*/
-			pixel_dst[3] = 0xff;
+	/* By default the start points are correct */
+	*src_x_start = src_line->x1;
+	*src_y_start = src_line->y1;
+	*dst_x_start = current_plane->frame_info->dst.x1;
+
+	/* Get the correct number of pixel to blend, it depends of the direction */
+	switch (direction) {
+	case READ_LEFT_TO_RIGHT:
+	case READ_RIGHT_TO_LEFT:
+		*pixel_count = drm_rect_width(src_line);
+		break;
+	case READ_BOTTOM_TO_TOP:
+	case READ_TOP_TO_BOTTOM:
+		*pixel_count = drm_rect_height(src_line);
+		break;
+	}
+
+	/*
+	 * Clamp the coordinates to avoid reading outside the buffer
+	 *
+	 * This is mainly a security check to avoid reading outside the buffer, the userspace
+	 * should never request to read outside the source buffer.
+	 */
+	switch (direction) {
+	case READ_LEFT_TO_RIGHT:
+	case READ_RIGHT_TO_LEFT:
+		if (*src_x_start < 0) {
+			*pixel_count += *src_x_start;
+			*dst_x_start -= *src_x_start;
+			*src_x_start = 0;
 		}
-		i_dst++;
+		if (*src_x_start + *pixel_count > current_plane->frame_info->fb->width)
+			*pixel_count = max(0, (int)current_plane->frame_info->fb->width -
+				*src_x_start);
+		break;
+	case READ_BOTTOM_TO_TOP:
+	case READ_TOP_TO_BOTTOM:
+		if (*src_y_start < 0) {
+			*pixel_count += *src_y_start;
+			*dst_x_start -= *src_y_start;
+			*src_y_start = 0;
+		}
+		if (*src_y_start + *pixel_count > current_plane->frame_info->fb->height)
+			*pixel_count = max(0, (int)current_plane->frame_info->fb->height -
+				*src_y_start);
+		break;
 	}
 }
 
-static void compose_plane(struct vkms_composer *primary_composer,
-			  struct vkms_composer *plane_composer,
-			  void *vaddr_out)
+/**
+ * blend_line() - Blend a line from a plane to the output buffer
+ *
+ * @current_plane: current plane to work on
+ * @y: line to write in the output buffer
+ * @crtc_x_limit: width of the output buffer
+ * @stage_buffer: temporary buffer to convert the pixel line from the source buffer
+ * @output_buffer: buffer to blend the read line into.
+ */
+static void blend_line(struct vkms_plane_state *current_plane, int y,
+		       int crtc_x_limit, struct line_buffer *stage_buffer,
+		       struct line_buffer *output_buffer)
 {
-	struct drm_gem_object *plane_obj;
-	struct drm_gem_shmem_object *plane_shmem_obj;
-	struct drm_framebuffer *fb = &plane_composer->fb;
-	void (*pixel_blend)(const u8 *p_src, u8 *p_dst);
+	int src_x_start, src_y_start, dst_x_start, pixel_count;
+	struct drm_rect dst_line, tmp_src, src_line;
+
+	/* Avoid rendering useless lines */
+	if (y < current_plane->frame_info->dst.y1 ||
+	    y >= current_plane->frame_info->dst.y2)
+		return;
+
+	/*
+	 * dst_line is the line to copy. The initial coordinates are inside the
+	 * destination framebuffer, and then drm_rect_* helpers are used to
+	 * compute the correct position into the source framebuffer.
+	 */
+	dst_line = DRM_RECT_INIT(current_plane->frame_info->dst.x1, y,
+				 drm_rect_width(&current_plane->frame_info->dst),
+				 1);
 
-	plane_obj = drm_gem_fb_get_obj(&plane_composer->fb, 0);
-	plane_shmem_obj = to_drm_gem_shmem_obj(plane_obj);
+	drm_rect_fp_to_int(&tmp_src, &current_plane->frame_info->src);
 
-	if (WARN_ON(!plane_shmem_obj->vaddr))
+	/*
+	 * [1]: Clamping src_line to the crtc_x_limit to avoid writing outside of
+	 * the destination buffer
+	 */
+	dst_line.x1 = max_t(int, dst_line.x1, 0);
+	dst_line.x2 = min_t(int, dst_line.x2, crtc_x_limit);
+	/* The destination is completely outside of the crtc. */
+	if (dst_line.x2 <= dst_line.x1)
 		return;
 
-	if (fb->format->format == DRM_FORMAT_ARGB8888)
-		pixel_blend = &alpha_blend;
-	else
-		pixel_blend = &x_blend;
+	src_line = dst_line;
+
+	/*
+	 * Transform the coordinate x/y from the crtc to coordinates into
+	 * coordinates for the src buffer.
+	 *
+	 * - Cancel the offset of the dst buffer.
+	 * - Invert the rotation. This assumes that
+	 *   dst = drm_rect_rotate(src, rotation) (dst and src have the
+	 *   same size, but can be rotated).
+	 * - Apply the offset of the source rectangle to the coordinate.
+	 */
+	drm_rect_translate(&src_line, -current_plane->frame_info->dst.x1,
+			   -current_plane->frame_info->dst.y1);
+	drm_rect_rotate_inv(&src_line, drm_rect_width(&tmp_src),
+			    drm_rect_height(&tmp_src),
+			    current_plane->frame_info->rotation);
+	drm_rect_translate(&src_line, tmp_src.x1, tmp_src.y1);
+
+	/* Get the correct reading direction in the source buffer. */
+
+	enum pixel_read_direction direction =
+		direction_for_rotation(current_plane->frame_info->rotation);
 
-	blend(vaddr_out, plane_shmem_obj->vaddr, primary_composer,
-	      plane_composer, pixel_blend);
+	/* [2]: Compute and clamp the number of pixel to read */
+	clamp_line_coordinates(direction, current_plane, &src_line, &src_x_start, &src_y_start,
+			       &dst_x_start, &pixel_count);
+
+	if (pixel_count <= 0) {
+		/* Nothing to read, so avoid multiple function calls */
+		return;
+	}
+
+	/*
+	 * Modify the starting point to take in account the rotation
+	 *
+	 * src_line is the top-left corner, so when reading READ_RIGHT_TO_LEFT or
+	 * READ_BOTTOM_TO_TOP, it must be changed to the top-right/bottom-left
+	 * corner.
+	 */
+	if (direction == READ_RIGHT_TO_LEFT) {
+		// src_x_start is now the right point
+		src_x_start += pixel_count - 1;
+	} else if (direction == READ_BOTTOM_TO_TOP) {
+		// src_y_start is now the bottom point
+		src_y_start += pixel_count - 1;
+	}
+
+	/*
+	 * Perform the conversion and the blending
+	 *
+	 * Here we know that the read line (x_start, y_start, pixel_count) is
+	 * inside the source buffer [2] and we don't write outside the stage
+	 * buffer [1].
+	 */
+	current_plane->pixel_read_line(current_plane, src_x_start, src_y_start, direction,
+				       pixel_count, &stage_buffer->pixels[dst_x_start]);
+	pre_blend_color_transform(current_plane, stage_buffer);
+	pre_mul_alpha_blend(stage_buffer, output_buffer,
+			    dst_x_start, pixel_count);
 }
 
-static int compose_active_planes(void **vaddr_out,
-				 struct vkms_composer *primary_composer,
-				 struct vkms_crtc_state *crtc_state)
+/**
+ * blend - blend the pixels from all planes and compute crc
+ * @wb: The writeback frame buffer metadata
+ * @crtc_state: The crtc state
+ * @crc32: The crc output of the final frame
+ * @output_buffer: A buffer of a row that will receive the result of the blend(s)
+ * @stage_buffer: The line with the pixels from plane being blend to the output
+ * @row_size: The size, in bytes, of a single row
+ *
+ * This function blends the pixels (Using the `pre_mul_alpha_blend`)
+ * from all planes, calculates the crc32 of the output from the former step,
+ * and, if necessary, convert and store the output to the writeback buffer.
+ */
+static void blend(struct vkms_writeback_job *wb,
+		  struct vkms_crtc_state *crtc_state,
+		  u32 *crc32, struct line_buffer *stage_buffer,
+		  struct line_buffer *output_buffer, size_t row_size)
 {
-	struct drm_framebuffer *fb = &primary_composer->fb;
-	struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
-	struct drm_gem_shmem_object *shmem_obj = to_drm_gem_shmem_obj(gem_obj);
-	int i;
-
-	if (!*vaddr_out) {
-		*vaddr_out = kzalloc(shmem_obj->base.size, GFP_KERNEL);
-		if (!*vaddr_out) {
-			DRM_ERROR("Cannot allocate memory for output frame.");
-			return -ENOMEM;
+	struct vkms_plane_state **plane = crtc_state->active_planes;
+	u32 n_active_planes = crtc_state->num_active_planes;
+
+	const struct pixel_argb_u16 background_color = { .a = 0xffff };
+
+	int crtc_y_limit = crtc_state->base.mode.vdisplay;
+	int crtc_x_limit = crtc_state->base.mode.hdisplay;
+
+	/*
+	 * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
+	 * complexity to avoid poor blending performance.
+	 *
+	 * The function pixel_read_line callback is used to read a line, using an efficient
+	 * algorithm for a specific format, into the staging buffer.
+	 */
+	for (int y = 0; y < crtc_y_limit; y++) {
+		fill_background(&background_color, output_buffer);
+
+		/* The active planes are composed associatively in z-order. */
+		for (size_t i = 0; i < n_active_planes; i++) {
+			blend_line(plane[i], y, crtc_x_limit, stage_buffer, output_buffer);
 		}
+
+		apply_lut(crtc_state, output_buffer);
+
+		*crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
+
+		if (wb)
+			vkms_writeback_row(wb, output_buffer, y);
 	}
+}
 
-	if (WARN_ON(!shmem_obj->vaddr))
-		return -EINVAL;
+static int check_format_funcs(struct vkms_crtc_state *crtc_state,
+			      struct vkms_writeback_job *active_wb)
+{
+	struct vkms_plane_state **planes = crtc_state->active_planes;
+	u32 n_active_planes = crtc_state->num_active_planes;
 
-	memcpy(*vaddr_out, shmem_obj->vaddr, shmem_obj->base.size);
+	for (size_t i = 0; i < n_active_planes; i++)
+		if (!planes[i]->pixel_read_line)
+			return -1;
 
-	/* If there are other planes besides primary, we consider the active
-	 * planes should be in z-order and compose them associatively:
-	 * ((primary <- overlay) <- cursor)
-	 */
-	for (i = 1; i < crtc_state->num_active_planes; i++)
-		compose_plane(primary_composer,
-			      crtc_state->active_planes[i]->composer,
-			      *vaddr_out);
+	if (active_wb && !active_wb->pixel_write)
+		return -1;
 
 	return 0;
 }
 
+static int check_iosys_map(struct vkms_crtc_state *crtc_state)
+{
+	struct vkms_plane_state **plane_state = crtc_state->active_planes;
+	u32 n_active_planes = crtc_state->num_active_planes;
+
+	for (size_t i = 0; i < n_active_planes; i++)
+		if (iosys_map_is_null(&plane_state[i]->frame_info->map[0]))
+			return -1;
+
+	return 0;
+}
+
+static int compose_active_planes(struct vkms_writeback_job *active_wb,
+				 struct vkms_crtc_state *crtc_state,
+				 u32 *crc32)
+{
+	size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
+	struct line_buffer output_buffer, stage_buffer;
+	int ret = 0;
+
+	/*
+	 * This check exists so we can call `crc32_le` for the entire line
+	 * instead doing it for each channel of each pixel in case
+	 * `struct `pixel_argb_u16` had any gap added by the compiler
+	 * between the struct fields.
+	 */
+	static_assert(sizeof(struct pixel_argb_u16) == 8);
+
+	if (WARN_ON(check_iosys_map(crtc_state)))
+		return -EINVAL;
+
+	if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
+		return -EINVAL;
+
+	line_width = crtc_state->base.mode.hdisplay;
+	stage_buffer.n_pixels = line_width;
+	output_buffer.n_pixels = line_width;
+
+	stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
+	if (!stage_buffer.pixels) {
+		DRM_ERROR("Cannot allocate memory for the output line buffer");
+		return -ENOMEM;
+	}
+
+	output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
+	if (!output_buffer.pixels) {
+		DRM_ERROR("Cannot allocate memory for intermediate line buffer");
+		ret = -ENOMEM;
+		goto free_stage_buffer;
+	}
+
+	blend(active_wb, crtc_state, crc32, &stage_buffer,
+	      &output_buffer, line_width * pixel_size);
+
+	kvfree(output_buffer.pixels);
+free_stage_buffer:
+	kvfree(stage_buffer.pixels);
+
+	return ret;
+}
+
 /**
  * vkms_composer_worker - ordered work_struct to compute CRC
  *
@@ -215,21 +588,19 @@ static int compose_active_planes(void **vaddr_out,
  *
  * Work handler for composing and computing CRCs. work_struct scheduled in
  * an ordered workqueue that's periodically scheduled to run by
- * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state().
+ * vkms_vblank_simulate() and flushed at vkms_atomic_commit_tail().
  */
 void vkms_composer_worker(struct work_struct *work)
 {
 	struct vkms_crtc_state *crtc_state = container_of(work,
-						struct vkms_crtc_state,
-						composer_work);
+							  struct vkms_crtc_state,
+							  composer_work);
 	struct drm_crtc *crtc = crtc_state->base.crtc;
+	struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
 	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
-	struct vkms_composer *primary_composer = NULL;
-	struct vkms_plane_state *act_plane = NULL;
 	bool crc_pending, wb_pending;
-	void *vaddr_out = NULL;
-	u32 crc32 = 0;
 	u64 frame_start, frame_end;
+	u32 crc32 = 0;
 	int ret;
 
 	spin_lock_irq(&out->composer_lock);
@@ -240,6 +611,22 @@ void vkms_composer_worker(struct work_struct *work)
 	crtc_state->frame_start = 0;
 	crtc_state->frame_end = 0;
 	crtc_state->crc_pending = false;
+
+	if (crtc->state->gamma_lut) {
+		s64 max_lut_index_fp;
+		s64 u16_max_fp = drm_int2fixp(0xffff);
+
+		crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
+		crtc_state->gamma_lut.lut_length =
+			crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
+		max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
+		crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
+									       u16_max_fp);
+
+	} else {
+		crtc_state->gamma_lut.base = NULL;
+	}
+
 	spin_unlock_irq(&out->composer_lock);
 
 	/*
@@ -249,35 +636,19 @@ void vkms_composer_worker(struct work_struct *work)
 	if (!crc_pending)
 		return;
 
-	if (crtc_state->num_active_planes >= 1) {
-		act_plane = crtc_state->active_planes[0];
-		if (act_plane->base.plane->type == DRM_PLANE_TYPE_PRIMARY)
-			primary_composer = act_plane->composer;
-	}
-
-	if (!primary_composer)
-		return;
-
 	if (wb_pending)
-		vaddr_out = crtc_state->active_writeback;
+		ret = compose_active_planes(active_wb, crtc_state, &crc32);
+	else
+		ret = compose_active_planes(NULL, crtc_state, &crc32);
 
-	ret = compose_active_planes(&vaddr_out, primary_composer,
-				    crtc_state);
-	if (ret) {
-		if (ret == -EINVAL && !wb_pending)
-			kfree(vaddr_out);
+	if (ret)
 		return;
-	}
-
-	crc32 = compute_crc(vaddr_out, primary_composer);
 
 	if (wb_pending) {
 		drm_writeback_signal_completion(&out->wb_connector, 0);
 		spin_lock_irq(&out->composer_lock);
 		crtc_state->wb_pending = false;
 		spin_unlock_irq(&out->composer_lock);
-	} else {
-		kfree(vaddr_out);
 	}
 
 	/*
@@ -287,7 +658,7 @@ void vkms_composer_worker(struct work_struct *work)
 		drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
 }
 
-static const char * const pipe_crc_sources[] = {"auto"};
+static const char *const pipe_crc_sources[] = { "auto" };
 
 const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
 					size_t *count)