[PATCH v12 08/15] drm/vkms: Re-introduce line-per-line composition algorithm
Maíra Canal
mairacanal at riseup.net
Sat Oct 26 14:26:24 UTC 2024
Hi Louis,
On 07/10/24 13:10, Louis Chauvet 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 at bootlin.com>
> Acked-by: Pekka Paalanen <pekka.paalanen at collabora.com>
>
> # Conflicts:
> # drivers/gpu/drm/vkms/vkms_composer.c
> ---
> 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(-)
>
[...]
>
> -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, at 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;
Why are you converting u8* to u8*? There are repetitions of this pattern
in this patch.
> + *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));
If you won't use rotated anymore, delete it from the struct.
Best Regards,
- Maíra
> 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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