[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 2:52 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 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. > > > 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? >
webOS, Roku OS, just to name a few. But most importantly, AMD has quite a few customers using "underlay" plane because of its YUV 420 capability. > >> 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 Thank you, Anatoliy
