[AMD Official Use Only - AMD Internal Distribution Only] Hi Sean,
> -----Original Message----- > From: Sean Anderson <[email protected]> > Sent: Monday, November 17, 2025 7:36 AM > To: Klymenko, Anatoliy <[email protected]>; Laurent Pinchart > <[email protected]>; Tomi Valkeinen > <[email protected]>; [email protected] > Cc: [email protected]; Mike Looijmans <[email protected]>; > David Airlie <[email protected]>; Thomas Zimmermann > <[email protected]>; Maarten Lankhorst > <[email protected]>; Maxime Ripard <[email protected]>; > [email protected]; Simona Vetter <[email protected]>; Simek, > Michal <[email protected]> > Subject: Re: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics > plane > > Caution: This message originated from an External Source. Use proper caution > when opening attachments, clicking links, or responding. > > > On 11/14/25 19:12, Klymenko, Anatoliy wrote: > > [AMD Official Use Only - AMD Internal Distribution Only] > > > >> -----Original Message----- > >> From: dri-devel <[email protected]> On Behalf Of > Sean > >> Anderson > >> Sent: Thursday, November 13, 2025 3:07 PM > >> To: Klymenko, Anatoliy <[email protected]>; Laurent Pinchart > >> <[email protected]>; Tomi Valkeinen > >> <[email protected]>; [email protected] > >> Cc: [email protected]; Mike Looijmans > <[email protected]>; > >> David Airlie <[email protected]>; Thomas Zimmermann > >> <[email protected]>; Maarten Lankhorst > >> <[email protected]>; Maxime Ripard > <[email protected]>; > >> [email protected]; Simona Vetter <[email protected]>; > Simek, > >> Michal <[email protected]> > >> Subject: Re: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics > >> plane > >> > >> Caution: This message originated from an External Source. Use proper > caution > >> when opening attachments, clicking links, or responding. > >> > >> > >> On 11/13/25 18:03, Klymenko, Anatoliy wrote: > >> > [AMD Official Use Only - AMD Internal Distribution Only] > >> > > >> > Hi Sean, > >> > > >> > Thank you for the patch. > >> > > >> >> -----Original Message----- > >> >> From: Sean Anderson <[email protected]> > >> >> Sent: Thursday, November 13, 2025 12:37 PM > >> >> To: Laurent Pinchart <[email protected]>; Tomi > Valkeinen > >> >> <[email protected]>; [email protected] > >> >> Cc: [email protected]; Mike Looijmans > >> <[email protected]>; > >> >> David Airlie <[email protected]>; Thomas Zimmermann > >> >> <[email protected]>; Maarten Lankhorst > >> >> <[email protected]>; Klymenko, Anatoliy > >> >> <[email protected]>; Maxime Ripard <[email protected]>; > >> linux- > >> >> [email protected]; Simona Vetter <[email protected]>; > Simek, > >> >> Michal <[email protected]>; Sean Anderson > >> >> <[email protected]> > >> >> Subject: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics > >> plane > >> >> > >> >> Caution: This message originated from an External Source. Use proper > >> caution > >> >> when opening attachments, clicking links, or responding. > >> >> > >> >> > >> >> When global alpha is enabled, per-pixel alpha is ignored. Allow > >> >> userspace to explicitly specify whether to use per-pixel alpha by > >> >> exposing it through the blend mode property. I'm not sure whether the > >> >> per-pixel alpha is pre-multiplied or not [1], but apparently it *must* > >> >> be > >> >> pre-multiplied so I guess we have to advertise it. > >> >> > >> >> [1] All we get is "The alpha value available with the graphics stream > >> >> will define the transparency of the graphics." > >> >> > >> >> Signed-off-by: Sean Anderson <[email protected]> > >> >> --- > >> >> > >> >> drivers/gpu/drm/xlnx/zynqmp_kms.c | 24 ++++++++++++++++++++++-- > >> >> 1 file changed, 22 insertions(+), 2 deletions(-) > >> >> > >> >> diff --git a/drivers/gpu/drm/xlnx/zynqmp_kms.c > >> >> b/drivers/gpu/drm/xlnx/zynqmp_kms.c > >> >> index 456ada9ac003..fa1cfc16db36 100644 > >> >> --- a/drivers/gpu/drm/xlnx/zynqmp_kms.c > >> >> +++ b/drivers/gpu/drm/xlnx/zynqmp_kms.c > >> >> @@ -61,6 +61,13 @@ static int > zynqmp_dpsub_plane_atomic_check(struct > >> >> drm_plane *plane, > >> >> if (!new_plane_state->crtc) > >> >> return 0; > >> >> > >> >> + if (new_plane_state->pixel_blend_mode != > >> >> DRM_MODE_BLEND_PIXEL_NONE && > >> >> + new_plane_state->alpha >> 8 != 0xff) { > >> >> + drm_dbg_kms(plane->dev, > >> >> + "Plane alpha must be 1.0 when using pixel > >> >> alpha\n"); > >> >> + return -EINVAL; > >> >> + } > >> >> + > >> >> crtc_state = drm_atomic_get_crtc_state(state, new_plane_state- > >crtc); > >> >> if (IS_ERR(crtc_state)) > >> >> return PTR_ERR(crtc_state); > >> >> @@ -117,9 +124,13 @@ static void > >> >> zynqmp_dpsub_plane_atomic_update(struct drm_plane *plane, > >> >> > >> >> zynqmp_disp_layer_update(layer, new_state); > >> >> > >> >> - if (plane->index == ZYNQMP_DPSUB_LAYER_GFX) > >> >> - zynqmp_disp_blend_set_global_alpha(dpsub->disp, true, > >> >> + if (plane->index == ZYNQMP_DPSUB_LAYER_GFX) { > >> >> + bool blend = plane->state->pixel_blend_mode == > >> >> + DRM_MODE_BLEND_PIXEL_NONE; > >> >> + > >> >> + zynqmp_disp_blend_set_global_alpha(dpsub->disp, blend, > >> >> plane->state->alpha > >> >> >> 8); > >> >> + } > >> >> > >> >> /* > >> >> * Unconditionally enable the layer, as it may have been > >> >> disabled > >> >> @@ -179,9 +190,18 @@ static int zynqmp_dpsub_create_planes(struct > >> >> zynqmp_dpsub *dpsub) > >> >> return ret; > >> >> > >> >> if (i == ZYNQMP_DPSUB_LAYER_GFX) { > >> >> + unsigned int blend_modes = > >> >> + BIT(DRM_MODE_BLEND_PIXEL_NONE) | > >> >> + BIT(DRM_MODE_BLEND_PREMULTI); > >> > > >> > | BIT(DRM_MODE_BLEND_COVERAGE) - this is what implemented in the > >> hardware. > >> > >> Do you have a datasheet (or other) reference? > >> > > > > Yes https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm > > There is no mention of this in the TRM. > > | Video Blending is defined for two RGB video streams. One of these > | streams will be graphics that have an alpha value along with RGB > | stream. The alpha value available with the graphics stream will define > | the transparency of the graphics. Alpha value defined for blending > | function is always 8-bit. 1-bit alpha and 4-bit alpha are also > | supported, but these are scaled to 8-bits before they are used for > | alpha blending > > Please quote a specific section where the alpha blending formula is > documented. > Yes, there is no explicit alpha blending formula in the TRM, although absence of "premultiplied alpha" term anywhere in the doc suggests that alpha is treated as a straight. Anyways, I cooked a quick test that proved the straight alpha theory: https://github.com/onotole/zynqmp-dp-alpha > >> But in any case, DRM_MODE_BLEND_PREMULTI is mandatory even if we > >> don't support > >> it. See drm_plane_create_blend_mode_property for details. > >> > > > > No doubts here > > OK, so regardless of what the hardware does, we have to pretend to > support pre-multiplied alpha. > Yes, we my pretend so, or we may work around backward compatibility check in drm_plane_create_blend_mode_property by setting blend mode to DRM_MODE_BLEND_COVERAGE immediately and later reject plane states with DRM_MODE_BLEND_PREMULTI mode. > --Sean Thank you, Anatoliy
