Hi Anatoliy, Sorry for the delay.
On 12/4/25 17:33, Klymenko, Anatoliy wrote: > [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 Does this matter? The z-order of the planes is fixed in hardware, no matter what software wishes it were. Regardless, the z-order does not change with this patch, so nothing should break. And from looking around in that repo, I cannot find any references to the primary plane, nor can I see any DRM calls. Plus, the purpose of the z-order stuff is to support punch-through rendering. But that can't work on ZynqMP without the following patch to fix the alpha channel. --Sean >> --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
