Re-introduce a line-by-line composition algorithm for each pixel format.
This allows more performance by not requiring an indirection per pixel
read. This patch is focused on readability of the code.

Line-by-line composition was introduced by [1] but rewritten back to
pixel-by-pixel algorithm in [2]. At this time, nobody noticed the impact
on performance, and it was merged.

This patch is almost a revert of [2], but in addition efforts have been
made to increase readability and maintainability of the rotation handling.
The blend function is now divided in two parts:
- Transformation of coordinates from the output referential to the source
referential
- Line conversion and blending

Most of the complexity of the rotation management is avoided by using
drm_rect_* helpers. The remaining complexity is around the clipping, to
avoid reading/writing outside source/destination buffers.

The pixel conversion is now done line-by-line, so the read_pixel_t was
replaced with read_pixel_line_t callback. This way the indirection is only
required once per line and per plane, instead of once per pixel and per
plane.

The read_line_t callbacks are very similar for most pixel format, but it
is required to avoid performance impact. Some helpers were created to
avoid code repetition:
- get_step_1x1: get the step in byte to reach next pixel block in a
  certain direction
- *_to_argb_u16: helpers to perform colors conversion. They should be
  inlined by the compiler, and they are used to avoid repetition between
  multiple variants of the same format (argb/xrgb and maybe in the
  future for formats like bgr formats).

This new algorithm was tested with:
- kms_plane (for color conversions)
- kms_rotation_crc (for rotations of planes)
- kms_cursor_crc (for translations of planes)
The performance gain was mesured with:
- kms_fb_stress

[1]: commit 8ba1648567e2 ("drm: vkms: Refactor the plane composer to accept
     new formats")
     https://lore.kernel.org/all/20220905190811.25024-7-igormtorre...@gmail.com/
[2]: commit 322d716a3e8a ("drm/vkms: isolate pixel conversion
     functionality")
     https://lore.kernel.org/all/20230418130525.128733-2-mca...@igalia.com/

Signed-off-by: Louis Chauvet <louis.chau...@bootlin.com>
---
 drivers/gpu/drm/vkms/vkms_composer.c | 169 ++++++++++++++++++++-------
 drivers/gpu/drm/vkms/vkms_drv.h      |  27 +++--
 drivers/gpu/drm/vkms/vkms_formats.c  | 218 +++++++++++++++++++++--------------
 drivers/gpu/drm/vkms/vkms_formats.h  |   2 +-
 drivers/gpu/drm/vkms/vkms_plane.c    |   5 +-
 5 files changed, 280 insertions(+), 141 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c 
b/drivers/gpu/drm/vkms/vkms_composer.c
index 068b6d838d7a..62122ade7d67 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -54,33 +54,6 @@ static void pre_mul_alpha_blend(
        }
 }
 
-static int get_y_pos(struct vkms_frame_info *frame_info, int y)
-{
-       if (frame_info->rotation & DRM_MODE_REFLECT_Y)
-               return drm_rect_height(&frame_info->rotated) - y - 1;
-
-       switch (frame_info->rotation & DRM_MODE_ROTATE_MASK) {
-       case DRM_MODE_ROTATE_90:
-               return frame_info->rotated.x2 - y - 1;
-       case DRM_MODE_ROTATE_270:
-               return y + frame_info->rotated.x1;
-       default:
-               return y;
-       }
-}
-
-static bool check_limit(struct vkms_frame_info *frame_info, int pos)
-{
-       if (drm_rotation_90_or_270(frame_info->rotation)) {
-               if (pos >= 0 && pos < drm_rect_width(&frame_info->rotated))
-                       return true;
-       } else {
-               if (pos >= frame_info->rotated.y1 && pos < 
frame_info->rotated.y2)
-                       return true;
-       }
-
-       return false;
-}
 
 static void fill_background(const struct pixel_argb_u16 *background_color,
                            struct line_buffer *output_buffer)
@@ -218,34 +191,150 @@ static void blend(struct vkms_writeback_job *wb,
 {
        struct vkms_plane_state **plane = crtc_state->active_planes;
        u32 n_active_planes = crtc_state->num_active_planes;
-       int y_pos, x_dst, x_limit;
 
        const struct pixel_argb_u16 background_color = { .a = 0xffff };
 
-       size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
+       int crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
+       int crtc_x_limit = crtc_state->base.crtc->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 vkms_compose_row is used to read a line, 
pixel-by-pixel, into the staging
-        * buffer.
+        * 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 (size_t 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++) {
-                       x_dst = plane[i]->frame_info->dst.x1;
-                       x_limit = min_t(size_t, 
drm_rect_width(&plane[i]->frame_info->dst),
-                                       stage_buffer->n_pixels);
-                       y_pos = get_y_pos(plane[i]->frame_info, y);
+                       struct vkms_plane_state *current_plane = plane[i];
 
-                       if (!check_limit(plane[i]->frame_info, y_pos))
+                       /* Avoid rendering useless lines */
+                       if (y < current_plane->frame_info->dst.y1 ||
+                           y >= current_plane->frame_info->dst.y2)
                                continue;
 
-                       vkms_compose_row(stage_buffer, plane[i], y_pos);
-                       pre_mul_alpha_blend(stage_buffer, output_buffer, x_dst, 
x_limit);
+                       /*
+                        * 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.
+                        */
+                       struct drm_rect dst_line = DRM_RECT_INIT(
+                               current_plane->frame_info->dst.x1, y,
+                               
drm_rect_width(&current_plane->frame_info->dst), 1);
+                       struct drm_rect tmp_src;
+
+                       drm_rect_fp_to_int(&tmp_src, 
&current_plane->frame_info->src);
+
+                       /*
+                        * [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)
+                               continue;
+
+                       struct drm_rect 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);
+
+                       int x_start = src_line.x1;
+                       int y_start = src_line.y1;
+                       int pixel_count;
+                       /* [2]: Compute and clamp the number of pixel to read */
+                       if (direction == READ_LEFT_TO_RIGHT || direction == 
READ_RIGHT_TO_LEFT) {
+                               /*
+                                * In horizontal reading, the src_line width is 
the number of pixel
+                                * to read
+                                */
+                               pixel_count = drm_rect_width(&src_line);
+                               if (x_start < 0) {
+                                       pixel_count += x_start;
+                                       x_start = 0;
+                               }
+                               if (x_start + pixel_count > 
current_plane->frame_info->fb->width) {
+                                       pixel_count =
+                                               
(int)current_plane->frame_info->fb->width - x_start;
+                               }
+                       } else {
+                               /*
+                                * In vertical reading, the src_line height is 
the number of pixel
+                                * to read
+                                */
+                               pixel_count = drm_rect_height(&src_line);
+                               if (y_start < 0) {
+                                       pixel_count += y_start;
+                                       y_start = 0;
+                               }
+                               if (y_start + pixel_count > 
current_plane->frame_info->fb->height) {
+                                       pixel_count =
+                                               
(int)current_plane->frame_info->fb->width - y_start;
+                               }
+                       }
+
+                       if (pixel_count <= 0) {
+                               /* Nothing to read, so avoid multiple function 
calls for nothing */
+                               continue;
+                       }
+
+                       /*
+                        * 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) {
+                               // x_start is now the right point
+                               x_start += pixel_count - 1;
+                       } else if (direction == READ_BOTTOM_TO_TOP) {
+                               // y_start is now the bottom point
+                               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,
+                               x_start,
+                               y_start,
+                               direction,
+                               pixel_count,
+                               
&stage_buffer->pixels[current_plane->frame_info->dst.x1]);
+
+                       pre_mul_alpha_blend(stage_buffer, output_buffer,
+                                           current_plane->frame_info->dst.x1,
+                                           pixel_count);
                }
 
                apply_lut(crtc_state, output_buffer);
@@ -253,7 +342,7 @@ static void blend(struct vkms_writeback_job *wb,
                *crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, 
row_size);
 
                if (wb)
-                       vkms_writeback_row(wb, output_buffer, y_pos);
+                       vkms_writeback_row(wb, output_buffer, y);
        }
 }
 
@@ -264,7 +353,7 @@ static int check_format_funcs(struct vkms_crtc_state 
*crtc_state,
        u32 n_active_planes = crtc_state->num_active_planes;
 
        for (size_t i = 0; i < n_active_planes; i++)
-               if (!planes[i]->pixel_read)
+               if (!planes[i]->pixel_read_line)
                        return -1;
 
        if (active_wb && !active_wb->pixel_write)
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 985e7a92b7bc..23e1d247468d 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -39,7 +39,6 @@
 struct vkms_frame_info {
        struct drm_framebuffer *fb;
        struct drm_rect src, dst;
-       struct drm_rect rotated;
        struct iosys_map map[DRM_FORMAT_MAX_PLANES];
        unsigned int rotation;
 };
@@ -80,26 +79,37 @@ enum pixel_read_direction {
        READ_LEFT_TO_RIGHT
 };
 
+struct vkms_plane_state;
+
 /**
- * typedef pixel_read_t - These functions are used to read a pixel in the 
source frame,
+ * typedef pixel_read_line_t - These functions are used to read a pixel line 
in the source frame,
  * convert it to `struct pixel_argb_u16` and write it to @out_pixel.
  *
- * @in_pixel: Pointer to the pixel to read
- * @out_pixel: Pointer to write the converted pixel
+ * @plane: Plane used as source for the pixel value
+ * @x_start: X (width) coordinate of the first pixel to copy. The caller must 
ensure that x_start
+ * is positive and smaller than @plane->frame_info->fb->width.
+ * @y_start: Y (width) coordinate of the first pixel to copy. The caller must 
ensure that y_start
+ * is positive and smaller than @plane->frame_info->fb->height.
+ * @direction: Direction to use for the copy, starting at @x_start/@y_start
+ * @count: Number of pixels to copy
+ * @out_pixel: Pointer where to write the pixel values. They will be written 
from @out_pixel[0]
+ * to @out_pixel[@count]. The caller must ensure that out_pixel have a length 
of at least @count.
  */
-typedef void (*pixel_read_t)(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel);
+typedef void (*pixel_read_line_t)(const struct vkms_plane_state *plane, int 
x_start,
+                                 int y_start, enum pixel_read_direction 
direction, int count,
+                                 struct pixel_argb_u16 out_pixel[]);
 
 /**
  * vkms_plane_state - Driver specific plane state
  * @base: base plane state
  * @frame_info: data required for composing computation
- * @pixel_read: function to read a pixel in this plane. The creator of a 
vkms_plane_state must
- * ensure that this pointer is valid
+ * @pixel_read_line: function to read a pixel line in this plane. The creator 
of a vkms_plane_state
+ * must ensure that this pointer is valid
  */
 struct vkms_plane_state {
        struct drm_shadow_plane_state base;
        struct vkms_frame_info *frame_info;
-       pixel_read_t pixel_read;
+       pixel_read_line_t pixel_read_line;
 };
 
 struct vkms_plane {
@@ -204,7 +214,6 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const 
char *source_name,
 /* Composer Support */
 void vkms_composer_worker(struct work_struct *work);
 void vkms_set_composer(struct vkms_output *out, bool enabled);
-void vkms_compose_row(struct line_buffer *stage_buffer, struct 
vkms_plane_state *plane, int y);
 void vkms_writeback_row(struct vkms_writeback_job *wb, const struct 
line_buffer *src_buffer, int y);
 
 /* Writeback */
diff --git a/drivers/gpu/drm/vkms/vkms_formats.c 
b/drivers/gpu/drm/vkms/vkms_formats.c
index 7a1bc1d8651f..87af3962ee12 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -90,74 +90,45 @@ static int get_step_1x1(struct drm_framebuffer *fb, enum 
pixel_read_direction di
        return 0;
 }
 
-static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int 
y,
-                                size_t plane_index)
-{
-       int x_src = frame_info->src.x1 >> 16;
-       int y_src = y - frame_info->rotated.y1 + (frame_info->src.y1 >> 16);
-
-       return packed_pixels_addr(frame_info, x_src, y_src, plane_index);
-}
-
-static int get_x_position(const struct vkms_frame_info *frame_info, int limit, 
int x)
-{
-       if (frame_info->rotation & (DRM_MODE_REFLECT_X | DRM_MODE_ROTATE_270))
-               return limit - x - 1;
-       return x;
-}
-
 /*
- * The following  functions take pixel data from the buffer and convert them 
to the format
+ * The following  functions take pixel data (a, r, g, b, pixel, ...), convert 
them to the format
  * ARGB16161616 in out_pixel.
  *
- * They are used in the `vkms_compose_row` function to handle multiple formats.
+ * They are used in the `read_line`s functions to avoid duplicate work for 
some pixel formats.
  */
 
-static void ARGB8888_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
+static struct pixel_argb_u16 argb_u16_from_u8888(int a, int r, int g, int b)
 {
+       struct pixel_argb_u16 out_pixel;
        /*
         * The 257 is the "conversion ratio". This number is obtained by the
         * (2^16 - 1) / (2^8 - 1) division. Which, in this case, tries to get
         * the best color value in a pixel format with more possibilities.
         * A similar idea applies to others RGB color conversions.
         */
-       out_pixel->a = (u16)in_pixel[3] * 257;
-       out_pixel->r = (u16)in_pixel[2] * 257;
-       out_pixel->g = (u16)in_pixel[1] * 257;
-       out_pixel->b = (u16)in_pixel[0] * 257;
-}
+       out_pixel.a = (u16)a * 257;
+       out_pixel.r = (u16)r * 257;
+       out_pixel.g = (u16)g * 257;
+       out_pixel.b = (u16)b * 257;
 
-static void XRGB8888_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
-{
-       out_pixel->a = (u16)0xffff;
-       out_pixel->r = (u16)in_pixel[2] * 257;
-       out_pixel->g = (u16)in_pixel[1] * 257;
-       out_pixel->b = (u16)in_pixel[0] * 257;
+       return out_pixel;
 }
 
-static void ARGB16161616_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
+static struct pixel_argb_u16 argb_u16_from_u16161616(int a, int r, int g, int 
b)
 {
-       u16 *pixel = (u16 *)in_pixel;
+       struct pixel_argb_u16 out_pixel;
 
-       out_pixel->a = le16_to_cpu(pixel[3]);
-       out_pixel->r = le16_to_cpu(pixel[2]);
-       out_pixel->g = le16_to_cpu(pixel[1]);
-       out_pixel->b = le16_to_cpu(pixel[0]);
-}
-
-static void XRGB16161616_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
-{
-       u16 *pixel = (u16 *)in_pixel;
+       out_pixel.a = le16_to_cpu(a);
+       out_pixel.r = le16_to_cpu(r);
+       out_pixel.g = le16_to_cpu(g);
+       out_pixel.b = le16_to_cpu(b);
 
-       out_pixel->a = (u16)0xffff;
-       out_pixel->r = le16_to_cpu(pixel[2]);
-       out_pixel->g = le16_to_cpu(pixel[1]);
-       out_pixel->b = le16_to_cpu(pixel[0]);
+       return out_pixel;
 }
 
-static void RGB565_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
+static struct pixel_argb_u16 argb_u16_from_RGB565(const u16 *pixel)
 {
-       u16 *pixel = (u16 *)in_pixel;
+       struct pixel_argb_u16 out_pixel;
 
        s64 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(31));
        s64 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(63));
@@ -167,12 +138,26 @@ static void RGB565_to_argb_u16(const u8 *in_pixel, struct 
pixel_argb_u16 *out_pi
        s64 fp_g = drm_int2fixp((rgb_565 >> 5) & 0x3f);
        s64 fp_b = drm_int2fixp(rgb_565 & 0x1f);
 
-       out_pixel->a = (u16)0xffff;
-       out_pixel->r = drm_fixp2int_round(drm_fixp_mul(fp_r, fp_rb_ratio));
-       out_pixel->g = drm_fixp2int_round(drm_fixp_mul(fp_g, fp_g_ratio));
-       out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
+       out_pixel.a = (u16)0xffff;
+       out_pixel.r = drm_fixp2int_round(drm_fixp_mul(fp_r, fp_rb_ratio));
+       out_pixel.g = drm_fixp2int_round(drm_fixp_mul(fp_g, fp_g_ratio));
+       out_pixel.b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
+
+       return out_pixel;
 }
 
+/*
+ * The following functions are read_line function for each pixel format 
supported by VKMS.
+ *
+ * They read a line starting at the point @x_start,@y_start following the 
@direction. The result
+ * is stored in @out_pixel and in the format ARGB16161616.
+ *
+ * Those function are very similar, but it is required for performance reason. 
In the past, some
+ * experiment were done, and with a generic loop the performance are very 
reduced [1].
+ *
+ * [1]: 
https://lore.kernel.org/dri-devel/d258c8dc-78e9-4509-9037-a98f7f33b...@riseup.net/
+ */
+
 /**
  * black_to_argb_u16() - pixel_read callback which always read black
  *
@@ -180,42 +165,101 @@ static void RGB565_to_argb_u16(const u8 *in_pixel, 
struct pixel_argb_u16 *out_pi
  * It is used to avoid null pointer to be used as a function. In theory, this 
function should
  * never be called, except if you found a bug in the driver/DRM core.
  */
-static void black_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 
*out_pixel)
+static void black_to_argb_u16(const struct vkms_plane_state *plane, int 
x_start,
+                             int y_start, enum pixel_read_direction direction, 
int count,
+                             struct pixel_argb_u16 out_pixel[])
 {
-       out_pixel->a = (u16) 0xFFFF;
-       out_pixel->r = 0;
-       out_pixel->g = 0;
-       out_pixel->b = 0;
+       struct pixel_argb_u16 *end = out_pixel + count;
+
+       while (out_pixel < end) {
+               *out_pixel = argb_u16_from_u8888(255, 0, 0, 0);
+               out_pixel += 1;
+       }
 }
 
-/**
- * vkms_compose_row - compose a single row of a plane
- * @stage_buffer: output line with the composed pixels
- * @plane: state of the plane that is being composed
- * @y: y coordinate of the row
- *
- * This function composes a single row of a plane. It gets the source pixels
- * through the y coordinate (see get_packed_src_addr()) and goes linearly
- * through the source pixel, reading the pixels and converting it to
- * ARGB16161616 (see the pixel_read() callback). For rotate-90 and rotate-270,
- * the source pixels are not traversed linearly. The source pixels are queried
- * on each iteration in order to traverse the pixels vertically.
- */
-void vkms_compose_row(struct line_buffer *stage_buffer, struct 
vkms_plane_state *plane, int y)
+static void ARGB8888_read_line(const struct vkms_plane_state *plane, int 
x_start, int y_start,
+                              enum pixel_read_direction direction, int count,
+                              struct pixel_argb_u16 out_pixel[])
+{
+       struct pixel_argb_u16 *end = out_pixel + count;
+       u8 *src_pixels = packed_pixels_addr(plane->frame_info, x_start, 
y_start, 0);
+
+       int step = get_step_1x1(plane->frame_info->fb, direction, 0);
+
+       while (out_pixel < end) {
+               u8 *px = (u8 *)src_pixels;
+               *out_pixel = argb_u16_from_u8888(px[3], px[2], px[1], px[0]);
+               out_pixel += 1;
+               src_pixels += step;
+       }
+}
+
+static void XRGB8888_read_line(const struct vkms_plane_state *plane, int 
x_start, int y_start,
+                              enum pixel_read_direction direction, int count,
+                              struct pixel_argb_u16 out_pixel[])
+{
+       struct pixel_argb_u16 *end = out_pixel + count;
+       u8 *src_pixels = packed_pixels_addr(plane->frame_info, x_start, 
y_start, 0);
+
+       int step = get_step_1x1(plane->frame_info->fb, direction, 0);
+
+       while (out_pixel < end) {
+               u8 *px = (u8 *)src_pixels;
+               *out_pixel = argb_u16_from_u8888(255, px[2], px[1], px[0]);
+               out_pixel += 1;
+               src_pixels += step;
+       }
+}
+
+static void ARGB16161616_read_line(const struct vkms_plane_state *plane, int 
x_start,
+                                  int y_start, enum pixel_read_direction 
direction, int count,
+                                  struct pixel_argb_u16 out_pixel[])
+{
+       struct pixel_argb_u16 *end = out_pixel + count;
+       u8 *src_pixels = packed_pixels_addr(plane->frame_info, x_start, 
y_start, 0);
+
+       int step = get_step_1x1(plane->frame_info->fb, direction, 0);
+
+       while (out_pixel < end) {
+               u16 *px = (u16 *)src_pixels;
+               *out_pixel = argb_u16_from_u16161616(px[3], px[2], px[1], 
px[0]);
+               out_pixel += 1;
+               src_pixels += step;
+       }
+}
+
+static void XRGB16161616_read_line(const struct vkms_plane_state *plane, int 
x_start,
+                                  int y_start, enum pixel_read_direction 
direction, int count,
+                                  struct pixel_argb_u16 out_pixel[])
+{
+       struct pixel_argb_u16 *end = out_pixel + count;
+       u8 *src_pixels = packed_pixels_addr(plane->frame_info, x_start, 
y_start, 0);
+
+       int step = get_step_1x1(plane->frame_info->fb, direction, 0);
+
+       while (out_pixel < end) {
+               u16 *px = (u16 *)src_pixels;
+               *out_pixel = argb_u16_from_u16161616(0xFFFF, px[2], px[1], 
px[0]);
+               out_pixel += 1;
+               src_pixels += step;
+       }
+}
+
+static void RGB565_read_line(const struct vkms_plane_state *plane, int x_start,
+                            int y_start, enum pixel_read_direction direction, 
int count,
+                            struct pixel_argb_u16 out_pixel[])
 {
-       struct pixel_argb_u16 *out_pixels = stage_buffer->pixels;
-       struct vkms_frame_info *frame_info = plane->frame_info;
-       u8 *src_pixels = get_packed_src_addr(frame_info, y, 0);
-       int limit = min_t(size_t, drm_rect_width(&frame_info->dst), 
stage_buffer->n_pixels);
+       struct pixel_argb_u16 *end = out_pixel + count;
+       u8 *src_pixels = packed_pixels_addr(plane->frame_info, x_start, 
y_start, 0);
 
-       for (size_t x = 0; x < limit; x++, src_pixels += 
frame_info->fb->format->cpp[0]) {
-               int x_pos = get_x_position(frame_info, limit, x);
+       int step = get_step_1x1(plane->frame_info->fb, direction, 0);
 
-               if (drm_rotation_90_or_270(frame_info->rotation))
-                       src_pixels = get_packed_src_addr(frame_info, x + 
frame_info->rotated.y1, 0)
-                               + frame_info->fb->format->cpp[0] * y;
+       while (out_pixel < end) {
+               u16 *px = (u16 *)src_pixels;
 
-               plane->pixel_read(src_pixels, &out_pixels[x_pos]);
+               *out_pixel = argb_u16_from_RGB565(px);
+               out_pixel += 1;
+               src_pixels += step;
        }
 }
 
@@ -321,25 +365,25 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
 }
 
 /**
- * Retrieve the correct read_pixel function for a specific format.
+ * Retrieve the correct read_line function for a specific format.
  * If the format is not supported by VKMS a warn is emitted and a dummy 
"always read black"
  * function is returned.
  *
  * @format: DRM_FORMAT_* value for which to obtain a conversion function (see 
[drm_fourcc.h])
  */
-pixel_read_t get_pixel_read_function(u32 format)
+pixel_read_line_t get_pixel_read_line_function(u32 format)
 {
        switch (format) {
        case DRM_FORMAT_ARGB8888:
-               return &ARGB8888_to_argb_u16;
+               return &ARGB8888_read_line;
        case DRM_FORMAT_XRGB8888:
-               return &XRGB8888_to_argb_u16;
+               return &XRGB8888_read_line;
        case DRM_FORMAT_ARGB16161616:
-               return &ARGB16161616_to_argb_u16;
+               return &ARGB16161616_read_line;
        case DRM_FORMAT_XRGB16161616:
-               return &XRGB16161616_to_argb_u16;
+               return &XRGB16161616_read_line;
        case DRM_FORMAT_RGB565:
-               return &RGB565_to_argb_u16;
+               return &RGB565_read_line;
        default:
                /*
                 * This is a bug in vkms_plane_atomic_check. All the supported
diff --git a/drivers/gpu/drm/vkms/vkms_formats.h 
b/drivers/gpu/drm/vkms/vkms_formats.h
index 3ecea4563254..8d2bef95ff79 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.h
+++ b/drivers/gpu/drm/vkms/vkms_formats.h
@@ -5,7 +5,7 @@
 
 #include "vkms_drv.h"
 
-pixel_read_t get_pixel_read_function(u32 format);
+pixel_read_line_t get_pixel_read_line_function(u32 format);
 
 pixel_write_t get_pixel_write_function(u32 format);
 
diff --git a/drivers/gpu/drm/vkms/vkms_plane.c 
b/drivers/gpu/drm/vkms/vkms_plane.c
index 10e9b23dab28..8875bed76410 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -112,7 +112,6 @@ static void vkms_plane_atomic_update(struct drm_plane 
*plane,
        frame_info = vkms_plane_state->frame_info;
        memcpy(&frame_info->src, &new_state->src, sizeof(struct drm_rect));
        memcpy(&frame_info->dst, &new_state->dst, sizeof(struct drm_rect));
-       memcpy(&frame_info->rotated, &new_state->dst, sizeof(struct drm_rect));
        frame_info->fb = fb;
        memcpy(&frame_info->map, &shadow_plane_state->data, 
sizeof(frame_info->map));
        drm_framebuffer_get(frame_info->fb);
@@ -122,10 +121,8 @@ static void vkms_plane_atomic_update(struct drm_plane 
*plane,
                                                                          
DRM_MODE_REFLECT_X |
                                                                          
DRM_MODE_REFLECT_Y);
 
-       drm_rect_rotate(&frame_info->rotated, 
drm_rect_width(&frame_info->rotated),
-                       drm_rect_height(&frame_info->rotated), 
frame_info->rotation);
 
-       vkms_plane_state->pixel_read = get_pixel_read_function(fmt);
+       vkms_plane_state->pixel_read_line = get_pixel_read_line_function(fmt);
 }
 
 static int vkms_plane_atomic_check(struct drm_plane *plane,

-- 
2.43.0

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