On 03/10/24 - 16:01, Harry Wentland wrote:
> Certain operations require us to preserve values below 0.0 and
> above 1.0 (0x0 and 0xffff respectively in 16 bpc unorm). One
> such operation is a BT709 encoding operation followed by its
> decoding operation, or the reverse.
>
> We'll use s32 values as intermediate in and outputs of our
> color operations, for the operations where it matters.
>
> For now this won't apply to LUT operations. We might want to
> update those to work on s32 as well, but it's unclear how
> that should work for unorm LUT definitions. We'll revisit
> that once we add LUT + CTM tests.
>
> In order to allow for this we'll also invert the nesting of our
> colorop processing loops. We now use the pixel iteration loop
> on the outside and the colorop iteration on the inside.
>
> Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
> ---
> v6:
> - use clamp_val instead of manual clamping (Louis Chauvet)
Perfect!
> v4:
> - Clarify that we're packing 16-bit UNORM into s32, not
> converting values to a different representation (Pekka)
>
> v3:
> - Use new colorop->next pointer
>
> drivers/gpu/drm/vkms/vkms_composer.c | 27 +++++++++++++++++++++++++--
> drivers/gpu/drm/vkms/vkms_drv.h | 4 ++++
> 2 files changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index b4aaad2bf45f..01fa81ebc93b 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -159,7 +159,7 @@ static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buff
> }
> }
>
> -static void apply_colorop(struct pixel_argb_u16 *pixel, struct drm_colorop *colorop)
> +static void apply_colorop(struct pixel_argb_s32 *pixel, struct drm_colorop *colorop)
I agree with this change, but I think we may face conversion issues
in apply_lut_to_channel_value, as it takes u16 and returns u16, but with
your change, you pass s32 and expect s32.
If it is not an issue: Reviewed-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> {
> struct drm_colorop_state *colorop_state = colorop->state;
>
> @@ -185,9 +185,26 @@ static void apply_colorop(struct pixel_argb_u16 *pixel, struct drm_colorop *colo
>
> static void pre_blend_color_transform(const struct vkms_plane_state *plane_state, struct line_buffer *output_buffer)
> {
> + struct pixel_argb_s32 pixel;
> +
> for (size_t x = 0; x < output_buffer->n_pixels; x++) {
> struct drm_colorop *colorop = plane_state->base.base.color_pipeline;
>
> + /*
> + * Some operations, such as applying a BT709 encoding matrix,
> + * followed by a decoding matrix, require that we preserve
> + * values above 1.0 and below 0.0 until the end of the pipeline.
> + *
> + * Pack the 16-bit UNORM values into s32 to give us head-room to
> + * avoid clipping until we're at the end of the pipeline. Clip
> + * intentionally at the end of the pipeline before packing
> + * UNORM values back into u16.
> + */
> + pixel.a = output_buffer->pixels[x].a;
> + pixel.r = output_buffer->pixels[x].r;
> + pixel.g = output_buffer->pixels[x].g;
> + pixel.b = output_buffer->pixels[x].b;
> +
> while (colorop) {
> struct drm_colorop_state *colorop_state;
>
> @@ -197,10 +214,16 @@ static void pre_blend_color_transform(const struct vkms_plane_state *plane_state
> return;
>
> if (!colorop_state->bypass)
> - apply_colorop(&output_buffer->pixels[x], colorop);
> + apply_colorop(&pixel, colorop);
>
> colorop = colorop->next;
> }
> +
> + /* clamp values */
> + output_buffer->pixels[x].a = clamp_val(pixel.a, 0, 0xffff);
> + output_buffer->pixels[x].r = clamp_val(pixel.r, 0, 0xffff);
> + output_buffer->pixels[x].g = clamp_val(pixel.g, 0, 0xffff);
> + output_buffer->pixels[x].b = clamp_val(pixel.b, 0, 0xffff);
> }
> }
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index 278cf3533f58..b78bc2611746 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -36,6 +36,10 @@ struct vkms_frame_info {
> unsigned int cpp;
> };
>
> +struct pixel_argb_s32 {
> + s32 a, r, g, b;
> +};
> +
> struct pixel_argb_u16 {
> u16 a, r, g, b;
> };
> --
> 2.46.2
>
