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Message-ID: <Zzt3O_hy5AgxYd81@louis-chauvet-laptop>
Date: Mon, 18 Nov 2024 18:19:55 +0100
From: Louis Chauvet <louis.chauvet@...tlin.com>
To: José Expósito <jose.exposito89@...il.com>
Cc: airlied@...il.com, arthurgrillo@...eup.net, corbet@....net,
dri-devel@...ts.freedesktop.org, hamohammed.sa@...il.com,
helen.koike@...labora.com, jeremie.dautheribes@...tlin.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
maarten.lankhorst@...ux.intel.com, mairacanal@...eup.net,
marcheu@...gle.com, melissa.srw@...il.com,
miquel.raynal@...tlin.com, mripard@...nel.org,
nicolejadeyee@...gle.com, pekka.paalanen@...labora.com,
pekka.paalanen@...oniitty.fi, rdunlap@...radead.org,
rodrigosiqueiramelo@...il.com, seanpaul@...gle.com,
simona.vetter@...ll.ch, simona@...ll.ch,
thomas.petazzoni@...tlin.com, tzimmermann@...e.de
Subject: Re: [PATCH v13 8/9] drm/vkms: Re-introduce line-per-line composition
algorithm
On 18/11/24 - 18:10, José Expósito wrote:
> > 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 for color
> > conversion were introduced to avoid code repetition:
> > - *_to_argb_u16: 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)
> > - kms_rotation (for all rotations and formats combinations) [3]
> > The performance gain was mesured with kms_fb_stress [4] with some
> > modification to fix the writeback format.
> >
> > The performance improvement is around 5 to 10%.
> >
> > [1]: commit 8ba1648567e2 ("drm: vkms: Refactor the plane composer to accept
> > new formats")
> > https://lore.kernel.org/all/20220905190811.25024-7-igormtorrente@gmail.com/
> > [2]: commit 322d716a3e8a ("drm/vkms: isolate pixel conversion
> > functionality")
> > https://lore.kernel.org/all/20230418130525.128733-2-mcanal@igalia.com/
> > [3]: https://lore.kernel.org/igt-dev/20240313-new_rotation-v2-0-6230fd5cae59@bootlin.com/
> > [4]: https://lore.kernel.org/all/20240422-kms_fb_stress-dev-v5-0-0c577163dc88@riseup.net/
> >
> > Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
> > Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>
> >
> > # Conflicts:
> > # drivers/gpu/drm/vkms/vkms_composer.c
> >
> > Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>
>
> checkpatch will complaint about this duplicated signature.
An other reason for a v14 :-)
I saw it when I tried to commit this series, thanks
> > ---
> > drivers/gpu/drm/vkms/vkms_composer.c | 234 ++++++++++++++++++++++++++++-------
> > drivers/gpu/drm/vkms/vkms_drv.h | 28 +++--
> > drivers/gpu/drm/vkms/vkms_formats.c | 224 ++++++++++++++++++++-------------
> > drivers/gpu/drm/vkms/vkms_formats.h | 2 +-
> > drivers/gpu/drm/vkms/vkms_plane.c | 5 +-
> > 5 files changed, 344 insertions(+), 149 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index 601e33431b45..7a3e47b895a7 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -29,8 +29,8 @@ static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
> > * @x_start: The start offset
> > * @pixel_count: The number of pixels to blend
> > *
> > - * The pixels [0;@pixel_count) in stage_buffer are blended at [@x_start;@x_start+@...el_count) in
> > - * output_buffer.
> > + * The pixels [@x_start;@x_start+@...el_count) in stage_buffer are blended at
> > + * [@x_start;@x_start+@...el_count) in output_buffer.
> > *
> > * The current DRM assumption is that pixel color values have been already
> > * pre-multiplied with the alpha channel values. See more
> > @@ -41,7 +41,7 @@ static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
> > struct line_buffer *output_buffer, int x_start, int pixel_count)
> > {
> > struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
> > - const struct pixel_argb_u16 *in = stage_buffer->pixels;
> > + const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];
> >
> > for (int i = 0; i < pixel_count; i++) {
> > out[i].a = (u16)0xffff;
> > @@ -51,33 +51,6 @@ static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
> > }
> > }
> >
> > -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)
> > @@ -203,6 +176,182 @@ static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
> > return READ_LEFT_TO_RIGHT;
> > }
> >
> > +/**
> > + * clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend
> > + * process.
> > + *
> > + * @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
> > + *
> > + * 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 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)
> > +{
> > + /* 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;
> > + }
> > + 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;
> > + }
> > +}
> > +
> > +/**
> > + * 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)
> > +{
> > + 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(¤t_plane->frame_info->dst),
> > + 1);
> > +
> > + drm_rect_fp_to_int(&tmp_src, ¤t_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)
> > + return;
> > +
> > + 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);
> > +
> > + /* [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_mul_alpha_blend(stage_buffer, output_buffer,
> > + dst_x_start, pixel_count);
> > +}
> > +
> > /**
> > * blend - blend the pixels from all planes and compute crc
> > * @wb: The writeback frame buffer metadata
> > @@ -223,34 +372,25 @@ 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, pixel_count;
> >
> > 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;
>
> I'm sure you are already aware of the tiny conflict with:
> https://lore.kernel.org/all/20241003-remove-legacy-v1-1-0b7db1f1a1a6@bootlin.com/
>
> This is now:
> - size_t crtc_y_limit = crtc_state->base.mode.vdisplay;
> + int crtc_y_limit = crtc_state->base.mode.vdisplay;
> + int crtc_x_limit = crtc_state->base.mode.hdisplay;
>
Yes, this is the main reason for v14... I was dumb and sent the v13 before
commiting the remove-legacy series... Next time I will commit and then
rebase, not the oposite :-)
> >
> > /*
> > * 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++) {
> > + 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++) {
> > - x_dst = plane[i]->frame_info->dst.x1;
> > - pixel_count = min_t(int, drm_rect_width(&plane[i]->frame_info->dst),
> > - (int)stage_buffer->n_pixels);
> > - y_pos = get_y_pos(plane[i]->frame_info, y);
> > -
> > - if (!check_limit(plane[i]->frame_info, y_pos))
> > - continue;
> > -
> > - vkms_compose_row(stage_buffer, plane[i], y_pos);
> > - pre_mul_alpha_blend(stage_buffer, output_buffer, x_dst, pixel_count);
> > + blend_line(plane[i], y, crtc_x_limit, stage_buffer, output_buffer);
> > }
> >
> > apply_lut(crtc_state, output_buffer);
> > @@ -258,7 +398,7 @@ 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);
> > }
> > }
> >
> > @@ -269,7 +409,7 @@ 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 777b7bd91f27..067a4797f7a0 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 +79,38 @@ 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 non-negative and smaller than @plane->frame_info->fb->width.
> > + * @y_start: Y (height) coordinate of the first pixel to copy. The caller must ensure that y_start
> > + * is non-negative and smaller than @plane->frame_info->fb->height.
> > + * @direction: direction to use for the copy, starting at @x_start/@...tart
> > + * @count: number of pixels to copy
> > + * @out_pixel: pointer where to write the pixel values. They will be written from @out_pixel[0]
> > + * (included) to @out_pixel[@count] (excluded). 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[]);
> >
> > /**
> > * struct 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 struct 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
> > + * struct 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 {
> > @@ -265,7 +276,6 @@ 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 d0e7dfc1f0d3..0f6678420a11 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -140,83 +140,51 @@ static void packed_pixels_addr_1x1(const struct vkms_frame_info *frame_info,
> > *addr = (u8 *)frame_info->map[0].vaddr + offset;
> > }
> >
> > -static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y,
> > - int plane_index)
> > -{
> > - int x_src = frame_info->src.x1 >> 16;
> > - int y_src = y - frame_info->rotated.y1 + (frame_info->src.y1 >> 16);
> > - u8 *addr;
> > - int rem_x, rem_y;
> > -
> > - WARN_ONCE(drm_format_info_block_width(frame_info->fb->format, plane_index) != 1,
> > - "%s() only support formats with block_w == 1", __func__);
> > - WARN_ONCE(drm_format_info_block_height(frame_info->fb->format, plane_index) != 1,
> > - "%s() only support formats with block_h == 1", __func__);
> > -
> > - packed_pixels_addr(frame_info, x_src, y_src, plane_index, &addr, &rem_x, &rem_y);
> > -
> > - return addr;
> > -}
> > -
> > -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
> > - * ARGB16161616 in @out_pixel.
> > + * The following functions take pixel data (a, r, g, b, pixel, ...) and convert them to
> > + * &struct pixel_argb_u16
> > *
> > - * 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(u8 a, u8 r, u8 g, u8 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(u16 a, u16 r, u16 g, u16 b)
> > {
> > - __le16 *pixel = (__le16 *)in_pixel;
> > + struct pixel_argb_u16 out_pixel;
> > +
> > + out_pixel.a = a;
> > + out_pixel.r = r;
> > + out_pixel.g = g;
> > + out_pixel.b = b;
> >
> > - 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]);
> > + return out_pixel;
> > }
> >
> > -static void XRGB16161616_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > +static struct pixel_argb_u16 argb_u16_from_le16161616(__le16 a, __le16 r, __le16 g, __le16 b)
> > {
> > - __le16 *pixel = (__le16 *)in_pixel;
> > -
> > - 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 argb_u16_from_u16161616(le16_to_cpu(a), le16_to_cpu(r), le16_to_cpu(g),
> > + le16_to_cpu(b));
> > }
> >
> > -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 __le16 *pixel)
> > {
> > - __le16 *pixel = (__le16 *)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));
> > @@ -226,40 +194,120 @@ 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;
> > }
> >
> > -/**
> > - * 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
> > +/*
> > + * 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.
> > + *
> > + * These functions are very repetitive, but the innermost pixel loops must be kept inside these
> > + * functions for performance reasons. Some benchmarking was done in [1] where having the innermost
> > + * loop factored out of these functions showed a slowdown by a factor of three.
> > *
> > - * 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.
> > + * [1]: https://lore.kernel.org/dri-devel/d258c8dc-78e9-4509-9037-a98f7f33b3a3@riseup.net/
> > */
> > -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 *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_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> > +
> > + int step = get_block_step_bytes(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_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> > +
> > + int step = get_block_step_bytes(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_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> > +
> > + int step = get_block_step_bytes(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_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> > +
> > + int step = get_block_step_bytes(plane->frame_info->fb, direction, 0);
> > +
> > + while (out_pixel < end) {
> > + __le16 *px = (__le16 *)src_pixels;
> > + *out_pixel = argb_u16_from_le16161616(cpu_to_le16(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 *end = out_pixel + count;
> > + u8 *src_pixels;
> > +
> > + packed_pixels_addr_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> >
> > - 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_block_step_bytes(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) {
> > + __le16 *px = (__le16 *)src_pixels;
> >
> > - plane->pixel_read(src_pixels, &out_pixels[x_pos]);
> > + *out_pixel = argb_u16_from_RGB565(px);
> > + out_pixel += 1;
> > + src_pixels += step;
> > }
> > }
> >
> > @@ -359,25 +407,25 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> > }
> >
> > /**
> > - * get_pixel_read_function() - Retrieve the correct read_pixel function for a specific
> > + * get_pixel_read_line_function() - Retrieve the correct read_line function for a specific
> > * format. The returned pointer is NULL for unsupported pixel formats. The caller must ensure that
> > * the pointer is valid before using it in a vkms_plane_state.
> > *
> > * @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,
> >
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