On 08/19, Igor Torrente wrote:
> Currently the blend function only accepts XRGB_8888 and ARGB_8888
> as a color input.
>
> This patch refactors all the functions related to the plane composition
> to overcome this limitation.
>
> The pixels blend is done using the new internal format. And new handlers
> are being added to convert a specific format to/from this internal format.
>
> So the blend operation depends on these handlers to convert to this common
> format. The blended result, if necessary, is converted to the writeback
> buffer format.
>
> This patch introduces three major differences to the blend function.
> 1 - All the planes are blended at once.
> 2 - The blend calculus is done as per line instead of per pixel.
> 3 - It is responsible to calculates the CRC and writing the writeback
> buffer(if necessary).
>
> These changes allow us to allocate way less memory in the intermediate
> buffer to compute these operations. Because now we don't need to
> have the entire intermediate image lines at once, just one line is
> enough.
>
> | Memory consumption (output dimensions) |
> |:--------------------------------------:|
> | Current | This patch |
> |:------------------:|:-----------------:|
> | Width * Heigth | 2 * Width |
>
> Beyond memory, we also have a minor performance benefit from all
> these changes. Results running the IGT[1] test
> `igt@kms_cursor_crc@pipe-a-cursor-512x512-onscreen` ten times:
>
> | Frametime |
> |:------------------------------------------:|
> | Implementation | Current | This commit |
> |:---------------:|:---------:|:------------:|
> | frametime range | 9~22 ms | 5~17 ms |
> | Average | 11.4 ms | 7.8 ms |
>
> [1] IGT commit id: bc3f6833a12221a46659535dac06ebb312490eb4
>
> V2: Improves the performance drastically, by performing the operations
> per-line and not per-pixel(Pekka Paalanen).
> Minor improvements(Pekka Paalanen).
> V3: Changes the code to blend the planes all at once. This improves
> performance, memory consumption, and removes much of the weirdness
> of the V2(Pekka Paalanen and me).
> Minor improvements(Pekka Paalanen and me).
> V4: Rebase the code and adapt it to the new NUM_OVERLAY_PLANES constant.
> V5: Minor checkpatch fixes and the removal of TO-DO item(Melissa Wen).
> Several security/robustness improvents(Pekka Paalanen).
> Removes check_planes_x_bounds function and allows partial
> partly off-screen(Pekka Paalanen).
> V6: Fix a mismatch of some variable sizes (Pekka Paalanen).
> Several minor improvements (Pekka Paalanen).
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Igor Torrente <igormtorrente@xxxxxxxxx>
> ---
> Documentation/gpu/vkms.rst | 4 -
> drivers/gpu/drm/vkms/Makefile | 1 +
> drivers/gpu/drm/vkms/vkms_composer.c | 320 ++++++++++++--------------
> drivers/gpu/drm/vkms/vkms_formats.c | 155 +++++++++++++
> drivers/gpu/drm/vkms/vkms_formats.h | 12 +
> drivers/gpu/drm/vkms/vkms_plane.c | 3 +
> drivers/gpu/drm/vkms/vkms_writeback.c | 3 +
> 7 files changed, 317 insertions(+), 181 deletions(-)
> create mode 100644 drivers/gpu/drm/vkms/vkms_formats.c
> create mode 100644 drivers/gpu/drm/vkms/vkms_formats.h
>
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index 973e2d43108b..a49e4ae92653 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -118,10 +118,6 @@ Add Plane Features
>
> There's lots of plane features we could add support for:
>
> -- Clearing primary plane: clear primary plane before plane composition (at the
> - start) for correctness of pixel blend ops. It also guarantees alpha channel
> - is cleared in the target buffer for stable crc. [Good to get started]
> -
> - ARGB format on primary plane: blend the primary plane into background with
> translucent alpha.
>
> diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> index 72f779cbfedd..1b28a6a32948 100644
> --- a/drivers/gpu/drm/vkms/Makefile
> +++ b/drivers/gpu/drm/vkms/Makefile
> @@ -3,6 +3,7 @@ vkms-y := \
> vkms_drv.o \
> vkms_plane.o \
> vkms_output.o \
> + vkms_formats.o \
> vkms_crtc.o \
> vkms_composer.o \
> vkms_writeback.o
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index b9fb408e8973..5b1a8bdd8268 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -7,204 +7,188 @@
> #include <drm/drm_fourcc.h>
> #include <drm/drm_gem_framebuffer_helper.h>
> #include <drm/drm_vblank.h>
> +#include <linux/minmax.h>
>
> #include "vkms_drv.h"
>
> -static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
> - const struct vkms_frame_info *frame_info)
> +static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
> {
> - u32 pixel;
> - int src_offset = frame_info->offset + (y * frame_info->pitch)
> - + (x * frame_info->cpp);
> + u32 new_color;
>
> - pixel = *(u32 *)&buffer[src_offset];
> + new_color = (src * 0xffff + dst * (0xffff - alpha));
>
> - return pixel;
> + return DIV_ROUND_CLOSEST(new_color, 0xffff);
> }
>
> /**
> - * compute_crc - Compute CRC value on output frame
> + * pre_mul_alpha_blend - alpha blending equation
> + * @src_frame_info: source framebuffer's metadata
> + * @stage_buffer: The line with the pixels from src_plane
> + * @output_buffer: A line buffer that receives all the blends output
> *
> - * @vaddr: address to final framebuffer
> - * @frame_info: framebuffer's metadata
> + * Using the information from the `frame_info`, this blends only the
> + * necessary pixels from the `stage_buffer` to the `output_buffer`
> + * using premultiplied blend formula.
> *
> - * returns CRC value computed using crc32 on the visible portion of
> - * the final framebuffer at vaddr_out
> + * The current DRM assumption is that pixel color values have been already
> + * pre-multiplied with the alpha channel values. See more
> + * drm_plane_create_blend_mode_property(). Also, this formula assumes a
> + * completely opaque background.
> */
> -static uint32_t compute_crc(const u8 *vaddr,
> - const struct vkms_frame_info *frame_info)
> +static void pre_mul_alpha_blend(struct vkms_frame_info *frame_info,
> + struct line_buffer *stage_buffer,
> + struct line_buffer *output_buffer)
> {
> - int x, y;
> - u32 crc = 0, pixel = 0;
> - int x_src = frame_info->src.x1 >> 16;
> - int y_src = frame_info->src.y1 >> 16;
> - int h_src = drm_rect_height(&frame_info->src) >> 16;
> - int w_src = drm_rect_width(&frame_info->src) >> 16;
> -
> - for (y = y_src; y < y_src + h_src; ++y) {
> - for (x = x_src; x < x_src + w_src; ++x) {
> - pixel = get_pixel_from_buffer(x, y, vaddr, frame_info);
> - crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
> - }
> + int x_dst = frame_info->dst.x1;
> + struct pixel_argb_u16 *out = output_buffer->pixels + x_dst;
> + struct pixel_argb_u16 *in = stage_buffer->pixels;
> + int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
> + stage_buffer->n_pixels);
> +
> + for (int x = 0; x < x_limit; x++) {
> + out[x].a = (u16)0xffff;
> + out[x].r = pre_mul_blend_channel(in[x].r, out[x].r, in[x].a);
> + out[x].g = pre_mul_blend_channel(in[x].g, out[x].g, in[x].a);
> + out[x].b = pre_mul_blend_channel(in[x].b, out[x].b, in[x].a);
> }
> -
> - return crc;
> }
>
> -static u8 blend_channel(u8 src, u8 dst, u8 alpha)
> +static bool check_y_limit(struct vkms_frame_info *frame_info, int y)
> {
> - u32 pre_blend;
> - u8 new_color;
> -
> - pre_blend = (src * 255 + dst * (255 - alpha));
> -
> - /* Faster div by 255 */
> - new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8);
> + if (y >= frame_info->dst.y1 && y < frame_info->dst.y2)
> + return true;
>
> - return new_color;
> + return false;
> }
>
> /**
> - * alpha_blend - alpha blending equation
> - * @argb_src: src pixel on premultiplied alpha mode
> - * @argb_dst: dst pixel completely opaque
> + * @wb_frame_info: The writeback frame buffer metadata
> + * @crtc_state: The crtc state
> + * @crc32: The crc output of the final frame
> + * @output_buffer: A buffer of a row that will receive the result of the blend(s)
> + * @stage_buffer: The line with the pixels from plane being blend to the output
> *
> - * blend pixels using premultiplied blend formula. The current DRM assumption
> - * is that pixel color values have been already pre-multiplied with the alpha
> - * channel values. See more drm_plane_create_blend_mode_property(). Also, this
> - * formula assumes a completely opaque background.
> + * This function blends the pixels (Using the `pre_mul_alpha_blend`)
> + * from all planes, calculates the crc32 of the output from the former step,
> + * and, if necessary, convert and store the output to the writeback buffer.
> */
> -static void alpha_blend(const u8 *argb_src, u8 *argb_dst)
> +static void blend(struct vkms_writeback_job *wb,
> + struct vkms_crtc_state *crtc_state,
> + u32 *crc32, struct line_buffer *stage_buffer,
> + struct line_buffer *output_buffer, size_t row_size)
> {
> - u8 alpha;
> + struct vkms_plane_state **plane = crtc_state->active_planes;
> + struct vkms_frame_info *primary_plane_info = plane[0]->frame_info;
> + u32 n_active_planes = crtc_state->num_active_planes;
> +
> + int y_dst = primary_plane_info->dst.y1;
> + int h_dst = drm_rect_height(&primary_plane_info->dst);
> + int y_limit = y_dst + h_dst;
> +
> + for (size_t y = y_dst; y < y_limit; y++) {
> + plane[0]->plane_read(output_buffer, primary_plane_info, y);
> +
> + /* If there are other planes besides primary, we consider the active
> + * planes should be in z-order and compose them associatively:
> + * ((primary <- overlay) <- cursor)
> + */
> + for (size_t i = 1; i < n_active_planes; i++) {
> + if (!check_y_limit(plane[i]->frame_info, y))
> + continue;
> +
> + plane[i]->plane_read(stage_buffer, plane[i]->frame_info, y);
> + pre_mul_alpha_blend(plane[i]->frame_info, stage_buffer,
> + output_buffer);
> + }
> +
> + *crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
>
> - alpha = argb_src[3];
> - argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], alpha);
> - argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], alpha);
> - argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], alpha);
> + if (wb)
> + wb->wb_write(&wb->wb_frame_info, output_buffer, y);
> + }
> }
>
> -/**
> - * x_blend - blending equation that ignores the pixel alpha
> - *
> - * overwrites RGB color value from src pixel to dst pixel.
> - */
> -static void x_blend(const u8 *xrgb_src, u8 *xrgb_dst)
> +static int check_format_funcs(struct vkms_crtc_state *crtc_state,
> + struct vkms_writeback_job *active_wb)
> {
> - memcpy(xrgb_dst, xrgb_src, sizeof(u8) * 3);
> + struct vkms_plane_state **planes = crtc_state->active_planes;
> + u32 n_active_planes = crtc_state->num_active_planes;
> +
> + for (size_t i = 0; i < n_active_planes; i++)
> + if (!planes[i]->plane_read)
> + return -1;
> +
> + if (active_wb && !active_wb->wb_write)
> + return -1;
> +
> + return 0;
> }
>
> -/**
> - * blend - blend value at vaddr_src with value at vaddr_dst
> - * @vaddr_dst: destination address
> - * @vaddr_src: source address
> - * @dst_frame_info: destination framebuffer's metadata
> - * @src_frame_info: source framebuffer's metadata
> - * @pixel_blend: blending equation based on plane format
> - *
> - * Blend the vaddr_src value with the vaddr_dst value using a pixel blend
> - * equation according to the supported plane formats DRM_FORMAT_(A/XRGB8888)
> - * and clearing alpha channel to an completely opaque background. This function
> - * uses buffer's metadata to locate the new composite values at vaddr_dst.
> - *
> - * TODO: completely clear the primary plane (a = 0xff) before starting to blend
> - * pixel color values
> - */
> -static void blend(void *vaddr_dst, void *vaddr_src,
> - struct vkms_frame_info *dst_frame_info,
> - struct vkms_frame_info *src_frame_info,
> - void (*pixel_blend)(const u8 *, u8 *))
> +static int compose_active_planes(struct vkms_writeback_job *active_wb,
> + struct vkms_crtc_state *crtc_state,
> + u32 *crc32)
> {
> - int i, j, j_dst, i_dst;
> - int offset_src, offset_dst;
> - u8 *pixel_dst, *pixel_src;
> -
> - int x_src = src_frame_info->src.x1 >> 16;
> - int y_src = src_frame_info->src.y1 >> 16;
> -
> - int x_dst = src_frame_info->dst.x1;
> - int y_dst = src_frame_info->dst.y1;
> - int h_dst = drm_rect_height(&src_frame_info->dst);
> - int w_dst = drm_rect_width(&src_frame_info->dst);
> -
> - int y_limit = y_src + h_dst;
> - int x_limit = x_src + w_dst;
> -
> - for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
> - for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
> - offset_dst = dst_frame_info->offset
> - + (i_dst * dst_frame_info->pitch)
> - + (j_dst++ * dst_frame_info->cpp);
> - offset_src = src_frame_info->offset
> - + (i * src_frame_info->pitch)
> - + (j * src_frame_info->cpp);
> -
> - pixel_src = (u8 *)(vaddr_src + offset_src);
> - pixel_dst = (u8 *)(vaddr_dst + offset_dst);
> - pixel_blend(pixel_src, pixel_dst);
> - /* clearing alpha channel (0xff)*/
> - pixel_dst[3] = 0xff;
> - }
> - i_dst++;
> + size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
> + struct vkms_frame_info *primary_plane_info = NULL;
> + struct line_buffer output_buffer, stage_buffer;
> + struct vkms_plane_state *act_plane = NULL;
> + int ret = 0;
> +
> + /*
> + * This check exists so we can call `crc32_le` for the entire line
> + * instead doing it for each channel of each pixel in case
> + * `struct `pixel_argb_u16` had any gap added by the compiler
> + * between the struct fields.
> + */
> + static_assert(sizeof(struct pixel_argb_u16) == 8);
> +
> + if (crtc_state->num_active_planes >= 1) {
> + act_plane = crtc_state->active_planes[0];
> + if (act_plane->base.base.plane->type == DRM_PLANE_TYPE_PRIMARY)
> + primary_plane_info = act_plane->frame_info;
> }
> -}
>
> -static void compose_plane(struct vkms_frame_info *primary_plane_info,
> - struct vkms_frame_info *plane_frame_info,
> - void *vaddr_out)
> -{
> - struct drm_framebuffer *fb = plane_frame_info->fb;
> - void *vaddr;
> - void (*pixel_blend)(const u8 *p_src, u8 *p_dst);
> + if (!primary_plane_info)
> + return -EINVAL;
>
> if (WARN_ON(iosys_map_is_null(&primary_plane_info->map[0])))
> - return;
> + return -EINVAL;
>
> - vaddr = plane_frame_info->map[0].vaddr;
> + if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
> + return -EINVAL;
>
> - if (fb->format->format == DRM_FORMAT_ARGB8888)
> - pixel_blend = &alpha_blend;
> - else
> - pixel_blend = &x_blend;
> + line_width = drm_rect_width(&primary_plane_info->dst);
> + stage_buffer.n_pixels = line_width;
> + output_buffer.n_pixels = line_width;
>
> - blend(vaddr_out, vaddr, primary_plane_info,
> - plane_frame_info, pixel_blend);
> -}
> + stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
> + if (!stage_buffer.pixels) {
> + DRM_ERROR("Cannot allocate memory for the output line buffer");
> + return -ENOMEM;
> + }
>
> -static int compose_active_planes(void **vaddr_out,
> - struct vkms_frame_info *primary_plane_info,
> - struct vkms_crtc_state *crtc_state)
> -{
> - struct drm_framebuffer *fb = primary_plane_info->fb;
> - struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
> - const void *vaddr;
> - int i;
> -
> - if (!*vaddr_out) {
> - *vaddr_out = kvzalloc(gem_obj->size, GFP_KERNEL);
> - if (!*vaddr_out) {
> - DRM_ERROR("Cannot allocate memory for output frame.");
> - return -ENOMEM;
> - }
> + output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
> + if (!output_buffer.pixels) {
> + DRM_ERROR("Cannot allocate memory for intermediate line buffer");
> + ret = -ENOMEM;
> + goto free_stage_buffer;
> }
>
> - if (WARN_ON(iosys_map_is_null(&primary_plane_info->map[0])))
> - return -EINVAL;
> + if (active_wb) {
> + struct vkms_frame_info *wb_frame_info = &active_wb->wb_frame_info;
>
> - vaddr = primary_plane_info->map[0].vaddr;
> + wb_frame_info->src = primary_plane_info->src;
> + wb_frame_info->dst = primary_plane_info->dst;
> + }
>
> - memcpy(*vaddr_out, vaddr, gem_obj->size);
> + blend(active_wb, crtc_state, crc32, &stage_buffer,
> + &output_buffer, line_width * pixel_size);
>
> - /* If there are other planes besides primary, we consider the active
> - * planes should be in z-order and compose them associatively:
> - * ((primary <- overlay) <- cursor)
> - */
> - for (i = 1; i < crtc_state->num_active_planes; i++)
> - compose_plane(primary_plane_info,
> - crtc_state->active_planes[i]->frame_info,
> - *vaddr_out);
> + kvfree(output_buffer.pixels);
> +free_stage_buffer:
> + kvfree(stage_buffer.pixels);
>
> - return 0;
> + return ret;
> }
>
> /**
> @@ -222,13 +206,11 @@ void vkms_composer_worker(struct work_struct *work)
> struct vkms_crtc_state,
> composer_work);
> struct drm_crtc *crtc = crtc_state->base.crtc;
> + struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
> struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> - struct vkms_frame_info *primary_plane_info = NULL;
> - struct vkms_plane_state *act_plane = NULL;
> bool crc_pending, wb_pending;
> - void *vaddr_out = NULL;
> - u32 crc32 = 0;
> u64 frame_start, frame_end;
> + u32 crc32 = 0;
> int ret;
>
> spin_lock_irq(&out->composer_lock);
> @@ -248,35 +230,19 @@ void vkms_composer_worker(struct work_struct *work)
> if (!crc_pending)
> return;
>
> - if (crtc_state->num_active_planes >= 1) {
> - act_plane = crtc_state->active_planes[0];
> - if (act_plane->base.base.plane->type == DRM_PLANE_TYPE_PRIMARY)
> - primary_plane_info = act_plane->frame_info;
> - }
> -
> - if (!primary_plane_info)
> - return;
> -
> if (wb_pending)
> - vaddr_out = crtc_state->active_writeback->data[0].vaddr;
> + ret = compose_active_planes(active_wb, crtc_state, &crc32);
> + else
> + ret = compose_active_planes(NULL, crtc_state, &crc32);
>
> - ret = compose_active_planes(&vaddr_out, primary_plane_info,
> - crtc_state);
> - if (ret) {
> - if (ret == -EINVAL && !wb_pending)
> - kvfree(vaddr_out);
> + if (ret)
> return;
> - }
> -
> - crc32 = compute_crc(vaddr_out, primary_plane_info);
>
> if (wb_pending) {
> drm_writeback_signal_completion(&out->wb_connector, 0);
> spin_lock_irq(&out->composer_lock);
> crtc_state->wb_pending = false;
> spin_unlock_irq(&out->composer_lock);
> - } else {
> - kvfree(vaddr_out);
> }
>
> /*
> diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
> new file mode 100644
> index 000000000000..ca4bfcac686b
> --- /dev/null
> +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +
> +#include <drm/drm_rect.h>
> +#include <linux/minmax.h>
> +
> +#include "vkms_formats.h"
> +
> +static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
> +{
> + return frame_info->offset + (y * frame_info->pitch)
> + + (x * frame_info->cpp);
> +}
> +
> +/*
> + * packed_pixels_addr - Get the pointer to pixel of a given pair of coordinates
> + *
> + * @frame_info: Buffer metadata
> + * @x: The x(width) coordinate of the 2D buffer
> + * @y: The y(Heigth) coordinate of the 2D buffer
> + *
> + * 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).
> + */
> +static void *packed_pixels_addr(const struct vkms_frame_info *frame_info,
> + int x, int y)
> +{
> + size_t offset = pixel_offset(frame_info, x, y);
> +
> + return (u8 *)frame_info->map[0].vaddr + offset;
> +}
> +
> +static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y)
> +{
> + int x_src = frame_info->src.x1 >> 16;
> + int y_src = y - frame_info->dst.y1 + (frame_info->src.y1 >> 16);
> +
> + return packed_pixels_addr(frame_info, x_src, y_src);
> +}
> +
> +static void ARGB8888_to_argb_u16(struct line_buffer *stage_buffer,
> + const struct vkms_frame_info *frame_info, int y)
> +{
> + struct pixel_argb_u16 *out_pixels = stage_buffer->pixels;
> + u8 *src_pixels = get_packed_src_addr(frame_info, y);
> + int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
> + stage_buffer->n_pixels);
> +
> + for (size_t x = 0; x < x_limit; x++, src_pixels += 4) {
> + /*
> + * 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_pixels[x].a = (u16)src_pixels[3] * 257;
> + out_pixels[x].r = (u16)src_pixels[2] * 257;
> + out_pixels[x].g = (u16)src_pixels[1] * 257;
> + out_pixels[x].b = (u16)src_pixels[0] * 257;
> + }
> +}
> +
> +static void XRGB8888_to_argb_u16(struct line_buffer *stage_buffer,
> + const struct vkms_frame_info *frame_info, int y)
> +{
> + struct pixel_argb_u16 *out_pixels = stage_buffer->pixels;
> + u8 *src_pixels = get_packed_src_addr(frame_info, y);
> + int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
> + stage_buffer->n_pixels);
> +
> + for (size_t x = 0; x < x_limit; x++, src_pixels += 4) {
> + out_pixels[x].a = (u16)0xffff;
> + out_pixels[x].r = (u16)src_pixels[2] * 257;
> + out_pixels[x].g = (u16)src_pixels[1] * 257;
> + out_pixels[x].b = (u16)src_pixels[0] * 257;
> + }
> +}
> +
> +/*
> + * The following functions take an line of argb_u16 pixels from the
> + * src_buffer, convert them to a specific format, and store them in the
> + * destination.
> + *
> + * They are used in the `compose_active_planes` to convert and store a line
> + * from the src_buffer to the writeback buffer.
> + */
> +static void argb_u16_to_ARGB8888(struct vkms_frame_info *frame_info,
> + const struct line_buffer *src_buffer, int y)
> +{
> + int x_dst = frame_info->dst.x1;
> + u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, 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);
> +
> + for (size_t x = 0; x < x_limit; x++, dst_pixels += 4) {
> + /*
> + * This sequence below is important because the format's byte order is
> + * in little-endian. In the case of the ARGB8888 the memory is
> + * organized this way:
> + *
> + * | Addr | = blue channel
> + * | Addr + 1 | = green channel
> + * | Addr + 2 | = Red channel
> + * | Addr + 3 | = Alpha channel
> + */
> + dst_pixels[3] = DIV_ROUND_CLOSEST(in_pixels[x].a, 257);
> + dst_pixels[2] = DIV_ROUND_CLOSEST(in_pixels[x].r, 257);
> + dst_pixels[1] = DIV_ROUND_CLOSEST(in_pixels[x].g, 257);
> + dst_pixels[0] = DIV_ROUND_CLOSEST(in_pixels[x].b, 257);
> + }
> +}
> +
> +static void argb_u16_to_XRGB8888(struct vkms_frame_info *frame_info,
> + const struct line_buffer *src_buffer, int y)
> +{
> + int x_dst = frame_info->dst.x1;
> + u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, 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);
> +
> + for (size_t x = 0; x < x_limit; x++, dst_pixels += 4) {
> + dst_pixels[3] = 0xff;
> + dst_pixels[2] = DIV_ROUND_CLOSEST(in_pixels[x].r, 257);
> + dst_pixels[1] = DIV_ROUND_CLOSEST(in_pixels[x].g, 257);
> + dst_pixels[0] = DIV_ROUND_CLOSEST(in_pixels[x].b, 257);
> + }
> +}
> +
> +frame_to_line_func get_frame_to_line_function(u32 format)
> +{
> + switch (format) {
> + case DRM_FORMAT_ARGB8888:
> + return &ARGB8888_to_argb_u16;
> + case DRM_FORMAT_XRGB8888:
> + return &XRGB8888_to_argb_u16;
> + default:
> + return NULL;
> + }
> +}
> +
> +line_to_frame_func get_line_to_frame_function(u32 format)
> +{
> + switch (format) {
> + case DRM_FORMAT_ARGB8888:
> + return &argb_u16_to_ARGB8888;
> + case DRM_FORMAT_XRGB8888:
> + return &argb_u16_to_XRGB8888;
> + default:
> + return NULL;
> + }
> +}
> diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h
> new file mode 100644
> index 000000000000..053ca42d5b31
> --- /dev/null
> +++ b/drivers/gpu/drm/vkms/vkms_formats.h
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +
> +#ifndef _VKMS_FORMATS_H_
> +#define _VKMS_FORMATS_H_
> +
> +#include "vkms_drv.h"
> +
> +frame_to_line_func get_frame_to_line_function(u32 format);
> +
> +line_to_frame_func get_line_to_frame_function(u32 format);
> +
> +#endif /* _VKMS_FORMATS_H_ */
> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> index 8adbfdc05e50..7a479a714565 100644
> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> @@ -10,6 +10,7 @@
> #include <drm/drm_plane_helper.h>
>
> #include "vkms_drv.h"
> +#include "vkms_formats.h"
^ this line no longer applies (needs to rebase), but I can manage it before apply to drm-misc-next
>
> static const u32 vkms_formats[] = {
> DRM_FORMAT_XRGB8888,
> @@ -100,6 +101,7 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> struct drm_shadow_plane_state *shadow_plane_state;
> struct drm_framebuffer *fb = new_state->fb;
> struct vkms_frame_info *frame_info;
> + u32 fmt = fb->format->format;
>
> if (!new_state->crtc || !fb)
> return;
> @@ -116,6 +118,7 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> frame_info->offset = fb->offsets[0];
> frame_info->pitch = fb->pitches[0];
> frame_info->cpp = fb->format->cpp[0];
> + vkms_plane_state->plane_read = get_frame_to_line_function(fmt);
> }
>
> static int vkms_plane_atomic_check(struct drm_plane *plane,
> diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c
> index c87f6c89e7b4..d2aabb52cb46 100644
> --- a/drivers/gpu/drm/vkms/vkms_writeback.c
> +++ b/drivers/gpu/drm/vkms/vkms_writeback.c
> @@ -11,6 +11,7 @@
> #include <drm/drm_gem_shmem_helper.h>
>
> #include "vkms_drv.h"
> +#include "vkms_formats.h"
>
> static const u32 vkms_wb_formats[] = {
> DRM_FORMAT_XRGB8888,
> @@ -123,6 +124,7 @@ static void vkms_wb_atomic_commit(struct drm_connector *conn,
> struct drm_framebuffer *fb = connector_state->writeback_job->fb;
> struct vkms_writeback_job *active_wb;
> struct vkms_frame_info *wb_frame_info;
> + u32 wb_format = fb->format->format;
>
> if (!conn_state)
> return;
> @@ -140,6 +142,7 @@ 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->wb_write = get_line_to_frame_function(wb_format);
> }
>
> static const struct drm_connector_helper_funcs vkms_wb_conn_helper_funcs = {
> --
> 2.30.2
>
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