On 12/4/25 16:16, Klymenko, Anatoliy wrote: > [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.
OK, I'll add a patch to allow blend mode without premulti for v2. The comment on the function says that it's a default for old userspace, but we don't have a userspace that expects a particular blend mode in the first place. --Sean
