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. --Sean [1] https://github.com/webosose/omx-components/blob/27b33e17c25023f2c7ffbbfda10169fb500dacdc/src/omxdrm/videorenderer.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
