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 <[email protected]>
Cc: Rodrigo Siqueira <[email protected]>
Cc: Haneen Mohammed <[email protected]>
Signed-off-by: Melissa Wen <[email protected]>
---
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++;
}
--
2.28.0
On Wed, 19 Aug 2020 17:53:36 -0300
Melissa Wen <[email protected]> wrote:
> 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 <[email protected]>
> Cc: Rodrigo Siqueira <[email protected]>
> Cc: Haneen Mohammed <[email protected]>
>
> Signed-off-by: Melissa Wen <[email protected]>
> ---
> 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];
Hi,
DRM pixel formats are often defined as "bits in a 32-bit word", but
here you are accessing it as an array of bytes. To me that looks
suspicious wrt. big-endian architectures.
Unfortunately I have again forgot how DRM pixel formats should be
interpreted on a big-endian machine, if I ever even understood it, so I
can't say if this is right or not.
Thanks,
pq
> + 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++;
> }
Hi Melissa,
First of all, thanks a lot for your patch!
Follows my inline comments.
On 08/19, Melissa Wen wrote:
> 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 <[email protected]>
> Cc: Rodrigo Siqueira <[email protected]>
> Cc: Haneen Mohammed <[email protected]>
>
> Signed-off-by: Melissa Wen <[email protected]>
> ---
> 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)
Use static here.
Also, replace c_src to src, c_dst to dst, and a_src to alpha.
> +{
> + u32 pre_blend;
> + u8 new_color;
> +
> + /* Premultiplied alpha blending - IGT + cairo context */
You can drop the part that says "IGT + cairo context", this explanation
better suit the commit message.
> + 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)
Use static.
Looks like that argb_src is a read-only variable, in this sense add
const.
> +{
> + u8 a_src;
> +
> + a_src = argb_src[3];
change a_src to alpha.
> + 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;
I suppose that p stands for "pixel", right? In this case how about use
pixel?
Best Regards
Rodrigo Siqueira
>
> 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++;
> }
> --
> 2.28.0
>
--
Rodrigo Siqueira
https://siqueira.tech
Hi Rodrigo,
Thanks for the review!
I just sent a v2 applying your suggestions.
Best Regards,
Melissa Wen
Melissa Wen
On Tue, Aug 25, 2020 at 12:04 AM Rodrigo Siqueira
<[email protected]> wrote:
>
> Hi Melissa,
>
> First of all, thanks a lot for your patch!
>
> Follows my inline comments.
>
> On 08/19, Melissa Wen wrote:
> > 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 <[email protected]>
> > Cc: Rodrigo Siqueira <[email protected]>
> > Cc: Haneen Mohammed <[email protected]>
> >
> > Signed-off-by: Melissa Wen <[email protected]>
> > ---
> > 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)
>
> Use static here.
>
> Also, replace c_src to src, c_dst to dst, and a_src to alpha.
>
> > +{
> > + u32 pre_blend;
> > + u8 new_color;
> > +
> > + /* Premultiplied alpha blending - IGT + cairo context */
>
> You can drop the part that says "IGT + cairo context", this explanation
> better suit the commit message.
>
> > + 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)
>
> Use static.
>
> Looks like that argb_src is a read-only variable, in this sense add
> const.
>
> > +{
> > + u8 a_src;
> > +
> > + a_src = argb_src[3];
>
> change a_src to alpha.
>
> > + 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;
>
> I suppose that p stands for "pixel", right? In this case how about use
> pixel?
>
> Best Regards
> Rodrigo Siqueira
>
> >
> > 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++;
> > }
> > --
> > 2.28.0
> >
>
> --
> Rodrigo Siqueira
> https://siqueira.tech