RE: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics plane

Klymenko, Anatoliy
2025-11-15T00:12:16Z

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of Sean
> Anderson
> Sent: Thursday, November 13, 2025 3:07 PM
> To: Klymenko, Anatoliy <Anatoliy.Klymenko@amd.com>; Laurent Pinchart
> <laurent.pinchart@ideasonboard.com>; Tomi Valkeinen
> <tomi.valkeinen@ideasonboard.com>; dri-devel@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org; Mike Looijmans <mike.looijmans@topic.nl>;
> David Airlie <airlied@gmail.com>; Thomas Zimmermann
> <tzimmermann@suse.de>; Maarten Lankhorst
> <maarten.lankhorst@linux.intel.com>; Maxime Ripard <mripard@kernel.org>;
> linux-arm-kernel@lists.infradead.org; Simona Vetter <simona@ffwll.ch>; Simek,
> Michal <michal.simek@amd.com>
> 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 <sean.anderson@linux.dev>
> >> Sent: Thursday, November 13, 2025 12:37 PM
> >> To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>; Tomi Valkeinen
> >> <tomi.valkeinen@ideasonboard.com>; dri-devel@lists.freedesktop.org
> >> Cc: linux-kernel@vger.kernel.org; Mike Looijmans
> <mike.looijmans@topic.nl>;
> >> David Airlie <airlied@gmail.com>; Thomas Zimmermann
> >> <tzimmermann@suse.de>; Maarten Lankhorst
> >> <maarten.lankhorst@linux.intel.com>; Klymenko, Anatoliy
> >> <Anatoliy.Klymenko@amd.com>; Maxime Ripard <mripard@kernel.org>;
> linux-
> >> arm-kernel@lists.infradead.org; Simona Vetter <simona@ffwll.ch>; Simek,
> >> Michal <michal.simek@amd.com>; Sean Anderson
> >> <sean.anderson@linux.dev>
> >> 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 <sean.anderson@linux.dev>
> >> ---
> >>
> >> 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

> 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

> --Sean

Thank you,
Anatoliy