The current VKMS blend function ignores alpha channel and just overwrites vaddr_src with vaddr_dst. This XRGB approach triggers a warning when running the kms_cursor_crc/cursor-alpha-transparent test case. In IGT tests, cairo_format_argb32 uses premultiplied alpha (according to documentation), so this patch considers premultiplied alpha colors to compose vaddr_src with vaddr_dst.
This change removes the following cursor-alpha-transparent warning: Suspicious CRC: All values are 0.
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 | 43 +++++++++++++++++++++------- 1 file changed, 33 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index 4f3b07a32b60..6aac962d3e2e 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)); } @@ -42,6 +40,32 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) return crc; }
+u8 blend_channel(u8 c_src, u8 c_dst, u8 a_src) +{ + u32 pre_blend; + u8 new_color; + + /* Premultiplied alpha blending - IGT + cairo context */ + pre_blend = (c_src * 255 + c_dst * (255 - a_src)); + + /* Faster div by 255 */ + new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8); + + return new_color; +} + +void alpha_blending(u8 *argb_src, u8 *argb_dst) +{ + u8 a_src; + + a_src = argb_src[3]; + argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], a_src); + argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], a_src); + argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], a_src); + /* Opaque primary */ + argb_dst[3] = 0xFF; +} + /** * blend - blend value at vaddr_src with value at vaddr_dst * @vaddr_dst: destination address @@ -50,12 +74,9 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) * @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. + * Currently, this function considers premultiplied alpha for blending, as used + * by Cairo. It 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, @@ -63,6 +84,7 @@ static void blend(void *vaddr_dst, void *vaddr_src, { int i, j, j_dst, i_dst; int offset_src, offset_dst; + u8 *p_dst, *p_src;
int x_src = src_composer->src.x1 >> 16; int y_src = src_composer->src.y1 >> 16; @@ -84,8 +106,9 @@ static void blend(void *vaddr_dst, void *vaddr_src, + (i * src_composer->pitch) + (j * src_composer->cpp);
- memcpy(vaddr_dst + offset_dst, - vaddr_src + offset_src, sizeof(u32)); + p_src = (u8 *)(vaddr_src + offset_src); + p_dst = (u8 *)(vaddr_dst + offset_dst); + alpha_blending(p_src, p_dst); } i_dst++; }