On 26/10/24 - 12:05, Maíra Canal wrote: > Hi Louis, > > On 14/08/24 05:42, Louis Chauvet wrote: > > Re-introduce a line-by-line writeback algorithm for each pixel format. > > This allows more performance by not requiring an indirection per pixel > > write. > > > > Line-by-line writeback 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 with some effort to avoid code > > duplication. Now only the loop is repeated, but it is required to have > > good performances. > > > > The performance gain is around 5 to 10%. > > > > [1]: https://lore.kernel.org/all/20211005201637.58563-7-igormtorrente@xxxxxxxxx/ > > [2]: https://lore.kernel.org/all/20230515135204.115393-4-mcanal@xxxxxxxxxx/ > > > > Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx> > > --- > > drivers/gpu/drm/vkms/vkms_composer.c | 17 +++++ > > drivers/gpu/drm/vkms/vkms_drv.h | 20 +++--- > > drivers/gpu/drm/vkms/vkms_formats.c | 117 +++++++++++++++++++++++++++------- > > drivers/gpu/drm/vkms/vkms_formats.h | 2 +- > > drivers/gpu/drm/vkms/vkms_writeback.c | 2 +- > > 5 files changed, 124 insertions(+), 34 deletions(-) > > > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > > index 76d4aa8a0ef6..f0cae142ac22 100644 > > --- a/drivers/gpu/drm/vkms/vkms_composer.c > > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > > @@ -176,6 +176,23 @@ static enum pixel_read_direction direction_for_rotation(unsigned int rotation) > > return READ_LEFT_TO_RIGHT; > > } > > +/** > > + * Write a line to the writeback buffer > + * > > + * @wb: Job where to insert the final image > > + * @src_buffer: Line to write > > + * @y: Row to write in the writeback buffer > > + */ > > Please, review the documentation using the kernel-doc format. > > > +static void vkms_writeback_row(struct vkms_writeback_job *wb, > > + const struct line_buffer *src_buffer, size_t y_start) > > +{ > > + struct vkms_frame_info *frame_info = &wb->wb_frame_info; > > + int x_start = frame_info->dst.x1; > > + int count = min_t(size_t, drm_rect_width(&frame_info->dst), src_buffer->n_pixels); > > + > > + wb->pixel_write(wb, src_buffer->pixels, count, x_start, y_start); > > +} > > + > > /** > > * clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend > > * process. > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > > index 3870e825da81..526bf5207524 100644 > > --- a/drivers/gpu/drm/vkms/vkms_drv.h > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > > @@ -52,20 +52,25 @@ struct line_buffer { > > struct pixel_argb_u16 *pixels; > > }; > > +struct vkms_writeback_job; > > /** > > - * typedef pixel_write_t - These functions are used to read a pixel from a > > - * &struct pixel_argb_u16, convert it in a specific format and write it in the @dst_pixels > > - * buffer. > > + * typedef pixel_write_line_t - These functions are used to read a pixel line from a > > + * struct pixel_argb_u16 buffer, convert it and write it in the @wb job. > > * > > - * @out_pixel: destination address to write the pixel > > - * @in_pixel: pixel to write > > + * @wb: the writeback job to write the output of the conversion > > + * @in_pixels: Source buffer containing the line to convert > > + * @count: The width of a line > > + * @x_start: The x (width) coordinate in the destination plane > > + * @y_start: The y (height) coordinate in the destination plane > > */ > > -typedef void (*pixel_write_t)(u8 *out_pixel, const struct pixel_argb_u16 *in_pixel); > > +typedef void (*pixel_write_line_t)(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *in_pixels, int count, int x_start, > > + int y_start); > > struct vkms_writeback_job { > > struct iosys_map data[DRM_FORMAT_MAX_PLANES]; > > struct vkms_frame_info wb_frame_info; > > - pixel_write_t pixel_write; > > + pixel_write_line_t pixel_write; > > }; > > /** > > @@ -232,7 +237,6 @@ 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_writeback_row(struct vkms_writeback_job *wb, const struct line_buffer *src_buffer, int y); > > /* Writeback */ > > int vkms_enable_writeback_connector(struct vkms_device *vkmsdev); > > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c > > index d1abfb1c3e3c..d1309f6d307f 100644 > > --- a/drivers/gpu/drm/vkms/vkms_formats.c > > +++ b/drivers/gpu/drm/vkms/vkms_formats.c > > @@ -587,7 +587,7 @@ static void planar_yuv_read_line(const struct vkms_plane_state *plane, int x_sta > > * The following functions take one &struct pixel_argb_u16 and convert it to a specific format. > > * The result is stored in @out_pixel. > > * > > - * They are used in vkms_writeback_row() to convert and store a pixel from the src_buffer to > > + * They are used in the `write_line` functions to convert and store a pixel from the src_buffer to > > * the writeback buffer. > > */ > > static void argb_u16_to_ARGB8888(u8 *out_pixel, const struct pixel_argb_u16 *in_pixel) > > @@ -654,28 +654,97 @@ static void argb_u16_to_RGB565(u8 *out_pixel, const struct pixel_argb_u16 *in_pi > > *pixel = cpu_to_le16(r << 11 | g << 5 | b); > > } > > -/** > > - * vkms_writeback_row() - Generic loop for all supported writeback format. It is executed just > > - * after the blending to write a line in the writeback buffer. > > +/* > > + * The following functions are write_line function for each pixel format supported by VKMS. > > + * > > + * They write a full line at index y. They must read data from the line src_pixels. > > + * > > + * The caller must ensure that count is not larger than the framebuffer and the src_pixels. > > + * > > + * 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]. > > * > > - * @wb: Job where to insert the final image > > - * @src_buffer: Line to write > > - * @y: Row to write in the writeback buffer > > + * [1]: https://lore.kernel.org/dri-devel/d258c8dc-78e9-4509-9037-a98f7f33b3a3@xxxxxxxxxx/ > > I'm not sure if a link is approriate here. It was to have some context about the comment. If someone wants to modify this in the future (for example, factorise again the code :)), he will have some informations. > > */ > > -void vkms_writeback_row(struct vkms_writeback_job *wb, > > - const struct line_buffer *src_buffer, int y) > > + > > +static void ARGB8888_write_line(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *src_pixels, int count, int x_start, > > + int y_start) > > { > > - struct vkms_frame_info *frame_info = &wb->wb_frame_info; > > - int x_dst = frame_info->dst.x1; > > u8 *dst_pixels; > > - int rem_x, rem_y; > > - packed_pixels_addr(frame_info, x_dst, y, 0, &dst_pixels, &rem_x, &rem_y); > > - 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); > > + packed_pixels_addr_1x1(&wb->wb_frame_info, x_start, y_start, 0, &dst_pixels); > > - for (size_t x = 0; x < x_limit; x++, dst_pixels += frame_info->fb->format->cpp[0]) > > - wb->pixel_write(dst_pixels, &in_pixels[x]); > > + while (count) { > > + argb_u16_to_ARGB8888(dst_pixels, src_pixels); > > + dst_pixels += wb->wb_frame_info.fb->format->char_per_block[0]; > > + src_pixels += 1; > > + count--; > > + } > > +} > > + > > +static void XRGB8888_write_line(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *src_pixels, int count, int x_start, > > + int y_start) > > +{ > > + u8 *dst_pixels; > > + > > + packed_pixels_addr_1x1(&wb->wb_frame_info, x_start, y_start, 0, &dst_pixels); > > + > > + while (count) { > > + argb_u16_to_XRGB8888(dst_pixels, src_pixels); > > + dst_pixels += wb->wb_frame_info.fb->format->char_per_block[0]; > > + src_pixels += 1; > > + count--; > > + } > > +} > > + > > +static void ARGB16161616_write_line(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *src_pixels, int count, int x_start, > > + int y_start) > > +{ > > + u8 *dst_pixels; > > + > > + packed_pixels_addr_1x1(&wb->wb_frame_info, x_start, y_start, 0, &dst_pixels); > > + > > + while (count) { > > + argb_u16_to_ARGB16161616(dst_pixels, src_pixels); > > + dst_pixels += wb->wb_frame_info.fb->format->char_per_block[0]; > > + src_pixels += 1; > > + count--; > > + } > > +} > > + > > +static void XRGB16161616_write_line(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *src_pixels, int count, int x_start, > > + int y_start) > > +{ > > + u8 *dst_pixels; > > + > > + packed_pixels_addr_1x1(&wb->wb_frame_info, x_start, y_start, 0, &dst_pixels); > > + > > + while (count) { > > + argb_u16_to_XRGB16161616(dst_pixels, src_pixels); > > + dst_pixels += wb->wb_frame_info.fb->format->char_per_block[0]; > > + src_pixels += 1; > > + count--; > > + } > > +} > > + > > +static void RGB565_write_line(struct vkms_writeback_job *wb, > > + struct pixel_argb_u16 *src_pixels, int count, int x_start, > > + int y_start) > > +{ > > + u8 *dst_pixels; > > + > > + packed_pixels_addr_1x1(&wb->wb_frame_info, x_start, y_start, 0, &dst_pixels); > > + > > + while (count) { > > + argb_u16_to_RGB565(dst_pixels, src_pixels); > > + dst_pixels += wb->wb_frame_info.fb->format->char_per_block[0]; > > + src_pixels += 1; > > + count--; > > + } > > } > > /** > > @@ -936,25 +1005,25 @@ void get_conversion_matrix_to_argb_u16(u32 format, > > } > > /** > > - * get_pixel_write_function() - Retrieve the correct write_pixel function for a specific format. > > + * get_pixel_write_function() - Retrieve the correct write_line function for a specific format. > > Correct the docs. Nice catch! Thanks, Louis Chauvet > Best Regards, > - Maíra > > > * The returned pointer is NULL for unsupported pixel formats. The caller must ensure that the > > * pointer is valid before using it in a vkms_writeback_job. > > * > > * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h]) > > */ > > -pixel_write_t get_pixel_write_function(u32 format) > > +pixel_write_line_t get_pixel_write_line_function(u32 format) > { > > switch (format) { > > case DRM_FORMAT_ARGB8888: > > - return &argb_u16_to_ARGB8888; > > + return &ARGB8888_write_line; > > case DRM_FORMAT_XRGB8888: > > - return &argb_u16_to_XRGB8888; > > + return &XRGB8888_write_line; > > case DRM_FORMAT_ARGB16161616: > > - return &argb_u16_to_ARGB16161616; > > + return &ARGB16161616_write_line; > > case DRM_FORMAT_XRGB16161616: > > - return &argb_u16_to_XRGB16161616; > > + return &XRGB16161616_write_line; > > case DRM_FORMAT_RGB565: > > - return &argb_u16_to_RGB565; > > + return &RGB565_write_line; > > default: > > /* > > * This is a bug in vkms_writeback_atomic_check. All the supported > > diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h > > index eeb208cdd6b1..852ab9a4cee5 100644 > > --- a/drivers/gpu/drm/vkms/vkms_formats.h > > +++ b/drivers/gpu/drm/vkms/vkms_formats.h > > @@ -7,7 +7,7 @@ > > pixel_read_line_t get_pixel_read_line_function(u32 format); > > -pixel_write_t get_pixel_write_function(u32 format); > > +pixel_write_line_t get_pixel_write_line_function(u32 format); > > void get_conversion_matrix_to_argb_u16(u32 format, enum drm_color_encoding encoding, > > enum drm_color_range range, > > diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c > > index c8582df1f739..f6ed3aa69af8 100644 > > --- a/drivers/gpu/drm/vkms/vkms_writeback.c > > +++ b/drivers/gpu/drm/vkms/vkms_writeback.c > > @@ -150,7 +150,7 @@ static void vkms_wb_atomic_commit(struct drm_connector *conn, > > crtc_state->wb_pending = true; > > spin_unlock_irq(&output->composer_lock); > > drm_writeback_queue_job(wb_conn, connector_state); > > - active_wb->pixel_write = get_pixel_write_function(wb_format); > > + active_wb->pixel_write = get_pixel_write_line_function(wb_format); > > drm_rect_init(&wb_frame_info->src, 0, 0, crtc_width, crtc_height); > > drm_rect_init(&wb_frame_info->dst, 0, 0, crtc_width, crtc_height); > > } > >
