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."
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v2: - static for local functions - const for the read-only variable argb_src - replaces variable names - drops unnecessary comment
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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++; }