| Message ID | 20200825114532.abzdooluny2ekzvm@smtp.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/vkms: add alpha-premultiplied color blending | expand |
Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> On 08/25, Melissa Wen wrote: > The VKMS blend function was ignoring the alpha channel and just > overwriting vaddr_src with vaddr_dst. This XRGB approach triggers a > warning when running the kms_cursor_crc/cursor-alpha-transparent test > case. In IGT, cairo_format_argb32 uses premultiplied alpha (according to > documentation). Also current DRM assumption is that alpha is > premultiplied. Therefore, this patch considers premultiplied alpha > blending eq to compose vaddr_src with vaddr_dst. > > This change removes the following cursor-alpha-transparent warning: > "Suspicious CRC: All values are 0." > > -- > > v2: > - static for local functions > - const for the read-only variable argb_src > - replaces variable names > - drops unnecessary comment > > -- > > Cc: Daniel Vetter <daniel@ffwll.ch> > Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> > Cc: Haneen Mohammed <hamohammed.sa@gmail.com> > > Signed-off-by: Melissa Wen <melissa.srw@gmail.com> > --- > drivers/gpu/drm/vkms/vkms_composer.c | 55 ++++++++++++++++++++-------- > 1 file changed, 39 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > index 4f3b07a32b60..eaecc5a6c5db 100644 > --- a/drivers/gpu/drm/vkms/vkms_composer.c > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > @@ -32,8 +32,6 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) > src_offset = composer->offset > + (i * composer->pitch) > + (j * composer->cpp); > - /* XRGB format ignores Alpha channel */ > - bitmap_clear(vaddr_out + src_offset, 24, 8); > crc = crc32_le(crc, vaddr_out + src_offset, > sizeof(u32)); > } > @@ -42,27 +40,51 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) > return crc; > } > > +static u8 blend_channel(u8 src, u8 dst, u8 alpha) > +{ > + 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); > + > + return new_color; > +} > + > +static void alpha_blending(const u8 *argb_src, u8 *argb_dst) > +{ > + u8 alpha; > + > + 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); > + /* Opaque primary */ > + argb_dst[3] = 0xFF; > +} > + > /** > * blend - blend value at vaddr_src with value at vaddr_dst > * @vaddr_dst: destination address > * @vaddr_src: source address > - * @dest_composer: destination framebuffer's metadata > + * @dst_composer: destination framebuffer's metadata > * @src_composer: source framebuffer's metadata > * > - * Blend value at vaddr_src with value at vaddr_dst. > - * Currently, this function write value of vaddr_src on value > - * at vaddr_dst using buffer's metadata to locate the new values > - * from vaddr_src and their destination at vaddr_dst. > - * > - * TODO: Use the alpha value to blend vaddr_src with vaddr_dst > - * instead of overwriting it. > + * Blend the vaddr_src value with the vaddr_dst value using the pre-multiplied > + * alpha blending equation, since DRM currently assumes that the pixel color > + * values have already been pre-multiplied with the alpha channel values. See > + * more drm_plane_create_blend_mode_property(). This function uses buffer's > + * metadata to locate the new composite values at vaddr_dst. > */ > static void blend(void *vaddr_dst, void *vaddr_src, > - struct vkms_composer *dest_composer, > + struct vkms_composer *dst_composer, > struct vkms_composer *src_composer) > { > int i, j, j_dst, i_dst; > int offset_src, offset_dst; > + u8 *pixel_dst, *pixel_src; > > int x_src = src_composer->src.x1 >> 16; > int y_src = src_composer->src.y1 >> 16; > @@ -77,15 +99,16 @@ static void blend(void *vaddr_dst, void *vaddr_src, > > 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 = dest_composer->offset > - + (i_dst * dest_composer->pitch) > - + (j_dst++ * dest_composer->cpp); > + offset_dst = dst_composer->offset > + + (i_dst * dst_composer->pitch) > + + (j_dst++ * dst_composer->cpp); > offset_src = src_composer->offset > + (i * src_composer->pitch) > + (j * src_composer->cpp); > > - memcpy(vaddr_dst + offset_dst, > - vaddr_src + offset_src, sizeof(u32)); > + pixel_src = (u8 *)(vaddr_src + offset_src); > + pixel_dst = (u8 *)(vaddr_dst + offset_dst); > + alpha_blending(pixel_src, pixel_dst); > } > i_dst++; > } > -- > 2.28.0 >
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index 4f3b07a32b60..eaecc5a6c5db 100644 --- a/drivers/gpu/drm/vkms/vkms_composer.c +++ b/drivers/gpu/drm/vkms/vkms_composer.c @@ -32,8 +32,6 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) src_offset = composer->offset + (i * composer->pitch) + (j * composer->cpp); - /* XRGB format ignores Alpha channel */ - bitmap_clear(vaddr_out + src_offset, 24, 8); crc = crc32_le(crc, vaddr_out + src_offset, sizeof(u32)); } @@ -42,27 +40,51 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) return crc; } +static u8 blend_channel(u8 src, u8 dst, u8 alpha) +{ + 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); + + return new_color; +} + +static void alpha_blending(const u8 *argb_src, u8 *argb_dst) +{ + u8 alpha; + + 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); + /* Opaque primary */ + argb_dst[3] = 0xFF; +} + /** * blend - blend value at vaddr_src with value at vaddr_dst * @vaddr_dst: destination address * @vaddr_src: source address - * @dest_composer: destination framebuffer's metadata + * @dst_composer: destination framebuffer's metadata * @src_composer: source framebuffer's metadata * - * Blend value at vaddr_src with value at vaddr_dst. - * Currently, this function write value of vaddr_src on value - * at vaddr_dst using buffer's metadata to locate the new values - * from vaddr_src and their destination at vaddr_dst. - * - * TODO: Use the alpha value to blend vaddr_src with vaddr_dst - * instead of overwriting it. + * Blend the vaddr_src value with the vaddr_dst value using the pre-multiplied + * alpha blending equation, since DRM currently assumes that the pixel color + * values have already been pre-multiplied with the alpha channel values. See + * more drm_plane_create_blend_mode_property(). This function uses buffer's + * metadata to locate the new composite values at vaddr_dst. */ static void blend(void *vaddr_dst, void *vaddr_src, - struct vkms_composer *dest_composer, + struct vkms_composer *dst_composer, struct vkms_composer *src_composer) { int i, j, j_dst, i_dst; int offset_src, offset_dst; + u8 *pixel_dst, *pixel_src; int x_src = src_composer->src.x1 >> 16; int y_src = src_composer->src.y1 >> 16; @@ -77,15 +99,16 @@ static void blend(void *vaddr_dst, void *vaddr_src, 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 = dest_composer->offset - + (i_dst * dest_composer->pitch) - + (j_dst++ * dest_composer->cpp); + offset_dst = dst_composer->offset + + (i_dst * dst_composer->pitch) + + (j_dst++ * dst_composer->cpp); offset_src = src_composer->offset + (i * src_composer->pitch) + (j * src_composer->cpp); - memcpy(vaddr_dst + offset_dst, - vaddr_src + offset_src, sizeof(u32)); + pixel_src = (u8 *)(vaddr_src + offset_src); + pixel_dst = (u8 *)(vaddr_dst + offset_dst); + alpha_blending(pixel_src, pixel_dst); } i_dst++; }
The VKMS blend function was ignoring the alpha channel and just overwriting vaddr_src with vaddr_dst. This XRGB approach triggers a warning when running the kms_cursor_crc/cursor-alpha-transparent test case. In IGT, cairo_format_argb32 uses premultiplied alpha (according to documentation). Also current DRM assumption is that alpha is premultiplied. Therefore, this patch considers premultiplied alpha blending eq to compose vaddr_src with vaddr_dst. This change removes the following cursor-alpha-transparent warning: "Suspicious CRC: All values are 0." -- v2: - static for local functions - const for the read-only variable argb_src - replaces variable names - drops unnecessary comment -- Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> Cc: Haneen Mohammed <hamohammed.sa@gmail.com> Signed-off-by: Melissa Wen <melissa.srw@gmail.com> --- drivers/gpu/drm/vkms/vkms_composer.c | 55 ++++++++++++++++++++-------- 1 file changed, 39 insertions(+), 16 deletions(-)