Re: [PATCH v2 5/9] drm/vkms: Re-introduce line-per-line composition algorithm
From: Maíra Canal
Date: Fri Feb 23 2024 - 06:50:01 EST
Hi Louis,
On 2/23/24 08:37, 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 focussed on readability of the code.
s/focussed/focused
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 maintenability of the rotation handling.
s/maintenability/maintainability
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 remaning complexity is around the clipping, to
s/remaning/remaining
avoid reading/writing oudside source/destination buffers.
s/oudside/outside
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-igormtorrente@xxxxxxxxx/
[2]: commit 322d716a3e8a ("drm/vkms: isolate pixel conversion
functionality")
https://lore.kernel.org/all/20230418130525.128733-2-mcanal@xxxxxxxxxx/
Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
---
[...]
+enum pixel_read_direction {
+ READ_UP,
+ READ_DOWN,
+ READ_LEFT,
+ READ_RIGHT
+};
+
/**
- * typedef pixel_read_t - These functions are used to read a pixel in the source frame,
+<<<<<<< HEAD
This doesn't compile.
Best Regards,
- Maíra
+ * 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.
*
- * @src_pixels: Pointer to the pixel to read
- * @out_pixel: Pointer to write the converted pixel
+ * @frame_info: Frame used as source for the pixel value
+ * @y: Y (height) coordinate in the source buffer
+ * @x_start: X (width) coordinate of the first pixel to copy
+ * @x_end: X (width) coordinate of the last pixel to copy
+ * @out_pixel: Pointer where to write the pixel value. Pixels will be written between x_start and
+ * x_end.
*/
-typedef void (*pixel_read_t)(u8 *src_pixels, struct pixel_argb_u16 *out_pixel);
+typedef void (*pixel_read_line_t)(struct vkms_frame_info *frame_info, 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
@@ -88,7 +100,7 @@ typedef void (*pixel_read_t)(u8 *src_pixels, struct pixel_argb_u16 *out_pixel);
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 {
@@ -193,7 +205,6 @@ 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 1f5aeba57ad6..46daea6d3ee9 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -11,21 +11,29 @@
/**
* packed_pixels_offset() - Get the offset of the block containing the pixel at coordinates x/y
- * in the first plane
*
* @frame_info: Buffer metadata
* @x: The x coordinate of the wanted pixel in the buffer
* @y: The y coordinate of the wanted pixel in the buffer
+ * @plane_index: The index of the plane to use
*
* The caller must be aware that this offset is not always a pointer to a pixel. If individual
* pixel values are needed, they have to be extracted from the resulting block.
*/
-static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
+static size_t packed_pixels_offset(const struct vkms_frame_info *frame_info, int x, int y,
+ size_t plane_index)
{
struct drm_framebuffer *fb = frame_info->fb;
-
- return fb->offsets[0] + (y * fb->pitches[0])
- + (x * fb->format->cpp[0]);
+ const struct drm_format_info *format = frame_info->fb->format;
+ /* Directly using x and y to multiply pitches and format->ccp is not sufficient because
+ * in some formats a block can represent multiple pixels.
+ *
+ * Dividing x and y by the block size allows to extract the correct offset of the block
+ * containing the pixel.
+ */
+ return fb->offsets[plane_index] +
+ (y / drm_format_info_block_width(format, plane_index)) * fb->pitches[plane_index] +
+ (x / drm_format_info_block_height(format, plane_index)) * format->char_per_block[plane_index];
}
/**
@@ -35,44 +43,56 @@ static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int
* @frame_info: Buffer metadata
* @x: The x(width) coordinate inside the plane
* @y: The y(height) coordinate inside the plane
+ * @plane_index: The index of the plane
*
- * Takes the information stored in the frame_info, a pair of coordinates, and
- * returns the address of the first color channel.
- * This function assumes the channels are packed together, i.e. a color channel
- * comes immediately after another in the memory. And therefore, this function
- * doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21).
+ * Takes the information stored in the frame_info, a pair of coordinates, and returns the address
+ * of the block containing this pixel.
+ * The caller must be aware that this pointer is sometimes not directly a pixel, it needs some
+ * additional work to extract pixel color from this block.
*/
static void *packed_pixels_addr(const struct vkms_frame_info *frame_info,
- int x, int y)
+ int x, int y, size_t plane_index)
{
- size_t offset = pixel_offset(frame_info, x, y);
-
- return (u8 *)frame_info->map[0].vaddr + offset;
+ return (u8 *)frame_info->map[0].vaddr + packed_pixels_offset(frame_info, x, y, plane_index);
}
-static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y)
+/**
+ * get_step_1x1() - Common helper to compute the correct step value between each pixel to read in a
+ * certain direction.
+ * This must be used only with format where blockh == blockw == 1.
+ * In the case when direction is not a valid pixel_read_direction, the returned step is 0, so you
+ * must not rely on this result to create a loop variant.
+ *
+ * @fb Framebuffer to iter on
+ * @direction Direction of the reading
+ */
+static int get_step_1x1(struct drm_framebuffer *fb, enum pixel_read_direction direction,
+ int 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);
+ switch (direction) {
+ default:
+ DRM_ERROR("Invalid direction for pixel reading: %d\n", direction);
+ return 0;
+ case READ_RIGHT:
+ return fb->format->char_per_block[plane_index];
+ case READ_LEFT:
+ return -fb->format->char_per_block[plane_index];
+ case READ_DOWN:
+ return (int)fb->pitches[plane_index];
+ case READ_UP:
+ return -(int)fb->pitches[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(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
+static void ARGB8888_to_argb_u16(struct pixel_argb_u16 *out_pixel, int a, int r, int g, int b)
{
/*
* The 257 is the "conversion ratio". This number is obtained by the
@@ -80,48 +100,26 @@ static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixe
* the best color value in a pixel format with more possibilities.
* A similar idea applies to others RGB color conversions.
*/
- out_pixel->a = (u16)src_pixels[3] * 257;
- out_pixel->r = (u16)src_pixels[2] * 257;
- out_pixel->g = (u16)src_pixels[1] * 257;
- out_pixel->b = (u16)src_pixels[0] * 257;
-}
-
-static void XRGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
-{
- out_pixel->a = (u16)0xffff;
- out_pixel->r = (u16)src_pixels[2] * 257;
- out_pixel->g = (u16)src_pixels[1] * 257;
- out_pixel->b = (u16)src_pixels[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 ARGB16161616_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
+static void ARGB16161616_to_argb_u16(struct pixel_argb_u16 *out_pixel, int a, int r, int g, int b)
{
- u16 *pixels = (u16 *)src_pixels;
-
- out_pixel->a = le16_to_cpu(pixels[3]);
- out_pixel->r = le16_to_cpu(pixels[2]);
- out_pixel->g = le16_to_cpu(pixels[1]);
- out_pixel->b = le16_to_cpu(pixels[0]);
-}
-
-static void XRGB16161616_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
-{
- u16 *pixels = (u16 *)src_pixels;
-
- out_pixel->a = (u16)0xffff;
- out_pixel->r = le16_to_cpu(pixels[2]);
- out_pixel->g = le16_to_cpu(pixels[1]);
- out_pixel->b = le16_to_cpu(pixels[0]);
+ 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);
}
-static void RGB565_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
+static void RGB565_to_argb_u16(struct pixel_argb_u16 *out_pixel, const u16 *pixel)
{
- u16 *pixels = (u16 *)src_pixels;
-
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));
- u16 rgb_565 = le16_to_cpu(*pixels);
+ u16 rgb_565 = le16_to_cpu(*pixel);
s64 fp_r = drm_int2fixp((rgb_565 >> 11) & 0x1f);
s64 fp_g = drm_int2fixp((rgb_565 >> 5) & 0x3f);
s64 fp_b = drm_int2fixp(rgb_565 & 0x1f);
@@ -132,34 +130,105 @@ static void RGB565_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
}
-/**
- * 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.
*
- * 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.
+ * 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-a98f7f33b3a3@xxxxxxxxxx/
*/
-void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state *plane, int y)
+
+static void ARGB8888_read_line(struct vkms_frame_info *frame_info, int x_start, int y_start,
+ enum pixel_read_direction direction, int count,
+ struct pixel_argb_u16 out_pixel[])
+{
+ u8 *src_pixels = packed_pixels_addr(frame_info, x_start, y_start, 0);
+
+ int step = get_step_1x1(frame_info->fb, direction, 0);
+
+ while (count) {
+ u8 *px = (u8 *)src_pixels;
+
+ ARGB8888_to_argb_u16(out_pixel, px[3], px[2], px[1], px[0]);
+ out_pixel += 1;
+ src_pixels += step;
+ count--;
+ }
+}
+
+static void XRGB8888_read_line(struct vkms_frame_info *frame_info, int x_start, int y_start,
+ enum pixel_read_direction direction, int count,
+ struct pixel_argb_u16 out_pixel[])
+{
+ u8 *src_pixels = packed_pixels_addr(frame_info, x_start, y_start, 0);
+
+ int step = get_step_1x1(frame_info->fb, direction, 0);
+
+ while (count) {
+ u8 *px = (u8 *)src_pixels;
+
+ ARGB8888_to_argb_u16(out_pixel, 255, px[2], px[1], px[0]);
+ out_pixel += 1;
+ src_pixels += step;
+ count--;
+ }
+}
+
+static void ARGB16161616_read_line(struct vkms_frame_info *frame_info, int x_start, int y_start,
+ enum pixel_read_direction direction, int count,
+ struct pixel_argb_u16 out_pixel[])
+{
+ u8 *src_pixels = packed_pixels_addr(frame_info, x_start, y_start, 0);
+
+ int step = get_step_1x1(frame_info->fb, direction, 0);
+
+ while (count) {
+ u16 *px = (u16 *)src_pixels;
+
+ ARGB16161616_to_argb_u16(out_pixel, px[3], px[2], px[1], px[0]);
+ out_pixel += 1;
+ src_pixels += step;
+ count--;
+ }
+}
+
+static void XRGB16161616_read_line(struct vkms_frame_info *frame_info, int x_start, int y_start,
+ enum pixel_read_direction direction, int count,
+ struct pixel_argb_u16 out_pixel[])
+{
+ u8 *src_pixels = packed_pixels_addr(frame_info, x_start, y_start, 0);
+
+ int step = get_step_1x1(frame_info->fb, direction, 0);
+
+ while (count) {
+ u16 *px = (u16 *)src_pixels;
+
+ ARGB16161616_to_argb_u16(out_pixel, 0xFFFF, px[2], px[1], px[0]);
+ out_pixel += 1;
+ src_pixels += step;
+ count--;
+ }
+}
+
+static void RGB565_read_line(struct vkms_frame_info *frame_info, 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);
- int limit = min_t(size_t, drm_rect_width(&frame_info->dst), stage_buffer->n_pixels);
+ u8 *src_pixels = packed_pixels_addr(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(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)
- + frame_info->fb->format->cpp[0] * y;
+ while (count) {
+ u16 *px = (u16 *)src_pixels;
- plane->pixel_read(src_pixels, &out_pixels[x_pos]);
+ RGB565_to_argb_u16(out_pixel, px);
+ out_pixel += 1;
+ src_pixels += step;
+ count--;
}
}
@@ -247,7 +316,7 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
{
struct vkms_frame_info *frame_info = &wb->wb_frame_info;
int x_dst = frame_info->dst.x1;
- u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, y);
+ u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, y, 0);
struct pixel_argb_u16 *in_pixels = src_buffer->pixels;
int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst), src_buffer->n_pixels);
@@ -256,27 +325,27 @@ 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.
* 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: 4cc of the format
*/
-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:
- return (pixel_read_t)NULL;
+ return (pixel_read_line_t)NULL;
}
}
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 f68b1b03d632..58c1c74742b5 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -106,9 +106,9 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
return;
fmt = fb->format->format;
- pixel_read_t pixel_read = get_pixel_read_function(fmt);
+ pixel_read_line_t pixel_read_line = get_pixel_read_line_function(fmt);
- if (!pixel_read) {
+ if (!pixel_read_line) {
DRM_WARN("Pixel format is not supported by VKMS planes. State is inchanged\n");
return;
}
@@ -128,10 +128,8 @@ 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 = pixel_read;
+ vkms_plane_state->pixel_read_line = pixel_read_line;
}
static int vkms_plane_atomic_check(struct drm_plane *plane,