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. >> 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. --Sean
