On 11/13/25 17:45, Klymenko, Anatoliy wrote: > [AMD Official Use Only - AMD Internal Distribution Only] > > Hi Sean, > > Thanks a lot for the patch (and tackling the alpha issue in general) > >> -----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 2/3] drm: zynqmp: Make the video plane primary >> >> Caution: This message originated from an External Source. Use proper caution >> when opening attachments, clicking links, or responding. >> >> >> The zynqmp has two planes: "video" and "graphics". The video plane >> >> - Is on the bottom (zpos=0) (except when chroma keying as the master plane) >> - Supports "live" input (e.g. from an external source) >> - Supports RGB, YUV, and YCbCr formats, including XRGB8888 >> - Does not support transparency, except via chroma keying (colorkey) >> - Must cover the entire screen (translation/resizing not supported) >> >> The graphics plane >> >> - Is on the top (zpos=1) >> - Supports "live" input (e.g. from an external source) >> - Supports RGB and YUV444 formats, but not XRGB8888 >> - Supports transparency either via >> - Global alpha channel, which disables per-pixel alpha when enabled >> - Per-pixel alpha, which cannot be used with global alpha >> - Chroma keying (colorkey) >> - Must cover the entire screen (translation/resizing not supported) >> >> Currently the graphics plane is the primary plane. Make the video plane >> the primary plane: >> >> - The video plane supports XRGB8888, which is the default 24-bit >> colorspace for X. This results in improved performance when compared >> to RGB565. >> - The graphics plane can be used as an overlay because it has a higher >> z-pos and supports a per-pixel alpha channel. Unfortunately, clients >> like weston cannot currently take advantage of this because they >> expect overlay planes to support translation/resizing. >> >> One downside to this approach could be that the graphics plane has worse >> support for YUV and YCBCr, so it may be more difficult to compose video > > Not just more difficult but practically impossible: > 1. GFX (in Xilinx terminology) plane doesn't support pixel upscaling, so > no support for NV12, YUY2 and other common video pixel formats. > 2. Both planes are unscalable, this means we can only output native > display resolution video on the top plane, or display thick black frame > around the picture. We are losing GFX masking capabilities.
The graphics masking capabilities are the same as they always were. > 3. We won't be able to render subtitles on top of the video. > Probably the only practical video player option remains here is to render > video to a texture and embed it into graphics composition. OK, but none of this is currently possible either because of the global alpha setting. So do you have a specific program in mind that plays video and will do it with an "underlay" plane? >> streams into the window of a media player. However, no existing software >> could rely on this because there is no way to enable the per-pixel alpha >> channel when the graphics plane is enabled. This makes it impossible to > > This situation is a driver bug not a fatum. And yet the driver bug provides ample evidence that no one is doing this, so we don't need to worry about it. --Sean > Per pixel alpha blending works > just fine if we disable global alpha. We just need to avoid enabling it when > we have alpha capable GFX plane format. > >> "carve out" an area in the graphics plane where the video plane shows >> through. This limitation is addressed in the next patch, but it means we >> do not need to worry about compatibility in this area. >> >> An alternate approach could be to pretend that the graphics plane >> supports XRGB8888 by using the supported ARGB8888 mode instead and >> enabling the global alpha channel. However, this would rule out ever >> using the per-pixel alpha channel. >> >> Signed-off-by: Sean Anderson <[email protected]> >> --- >> >> drivers/gpu/drm/xlnx/zynqmp_kms.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/gpu/drm/xlnx/zynqmp_kms.c >> b/drivers/gpu/drm/xlnx/zynqmp_kms.c >> index c80a2d4034f3..456ada9ac003 100644 >> --- a/drivers/gpu/drm/xlnx/zynqmp_kms.c >> +++ b/drivers/gpu/drm/xlnx/zynqmp_kms.c >> @@ -161,8 +161,8 @@ static int zynqmp_dpsub_create_planes(struct >> zynqmp_dpsub *dpsub) >> if (!formats) >> return -ENOMEM; >> >> - /* Graphics layer is primary, and video layer is overlay. */ >> - type = i == ZYNQMP_DPSUB_LAYER_VID >> + /* Graphics layer is overlay, and video layer is primary. */ >> + type = i == ZYNQMP_DPSUB_LAYER_GFX >> ? DRM_PLANE_TYPE_OVERLAY : >> DRM_PLANE_TYPE_PRIMARY; >> ret = drm_universal_plane_init(&dpsub->drm->dev, plane, 0, >> &zynqmp_dpsub_plane_funcs, >> @@ -322,7 +322,7 @@ static const struct drm_crtc_funcs >> zynqmp_dpsub_crtc_funcs = { >> >> static int zynqmp_dpsub_create_crtc(struct zynqmp_dpsub *dpsub) >> { >> - struct drm_plane *plane = &dpsub->drm- >> >planes[ZYNQMP_DPSUB_LAYER_GFX]; >> + struct drm_plane *plane = &dpsub->drm- >> >planes[ZYNQMP_DPSUB_LAYER_VID]; >> struct drm_crtc *crtc = &dpsub->drm->crtc; >> int ret; >> >> -- >> 2.35.1.1320.gc452695387.dirty > > Thank you, > Anatoliy
