[AMD Official Use Only - AMD Internal Distribution Only] Hi Sean,
> -----Original Message----- > From: Sean Anderson <[email protected]> > Sent: Monday, November 17, 2025 8:10 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 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 11/14/25 19:57, 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 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. > > Can you link to a specific example where the plane is selected based on > its primary/overlay status and not based on its format support? I'm not > too familiar with these distros, but e.g. [1] selects the plane based on > the format, and doesn't care which one is primary. > The plane selection by the type may not be explicit. For instance, if a graphics compositor uses legacy API with drmModeSetCrtc, it would allocate the primary plane implicitly. Or some compositor may just rely on planes z-order. For instance, here [2] you may see exact z-order WebOS compositor expects from the HW planes (both VideoPlane and FullscreenPlane are used for the video playback, the graphics lives on MainPlane). Anyways, the probability of primary plane being reserved for a graphics compositor is too high to ignore. Back to example [1], in our case the renderer would fail this check: if ((ovr->possible_crtcs & (1 << pipe)) && !ovr->crtc_id) for the primary plane pre-occupied by the graphics, and this check: if (!format_support(ovr, p->fourcc)) for the overlay plane lacking pixel upsampling support. [2] https://github.com/webosose/luna-surfacemanager/blob/b2fef6f73232244f6f13102aa66d2d3f5942835e/modules/weboscompositor/webossurfaceitem.cpp#L1794 > --Sean > > [1] https://github.com/webosose/omx- > components/blob/27b33e17c25023f2c7ffbbfda10169fb500dacdc/src/omxdrm/vid > eorenderer.cpp#L469 > > >> >> 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 Thank you, Anatoliy
