On Thursday, 11 December 2025 12:06:38 Central European Standard Time Chaoyi Chen wrote:

Hello Nicolas,

On 12/9/2025 6:58 PM, Nicolas Frattaroli wrote:

quoted

Hi Chaoyi Chen, Andy Yan,

On Monday, 8 December 2025 08:24:52 Central European Standard Time Nicolas Frattaroli wrote:

quoted

On Monday, 8 December 2025 03:48:24 Central European Standard Time Chaoyi Chen wrote:

quoted

Hello Nicolas, Daniel,

On 12/7/2025 4:45 AM, Nicolas Frattaroli wrote:

quoted

From: Daniel Stone <redacted>

Planes can only source AFBC framebuffers at multiples of 4px wide on
RK3566/RK3568. Instead of clipping on all SoCs when the user asks for an
unaligned source rectangle, reject the configuration in the plane's
atomic check on RK3566/RK3568 only.

Signed-off-by: Daniel Stone <redacted>
[Make RK3566/RK3568 specific, reword message]
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index bc1ed0ffede0..e23213337104 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c

@@ -1076,6 +1076,13 @@ static int vop2_plane_atomic_check(struct drm_plane *plane,
 		return -EINVAL;
 	}
 
+	if (vop2->version == VOP_VERSION_RK3568 && drm_is_afbc(fb->modifier) && src_w % 4) {
+		drm_dbg_kms(vop2->drm,
+			    "AFBC source rectangles must be 4-byte aligned; is %d\n",
+			    src_w);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 

@@ -1237,11 +1244,8 @@ static void vop2_plane_atomic_update(struct drm_plane *plane,
 	WARN_ON(src_w < 4);
 	WARN_ON(src_h < 4);
 
-	if (afbc_en && src_w % 4) {
-		drm_dbg_kms(vop2->drm, "vp%d %s src_w[%d] not 4 pixel aligned\n",
-			    vp->id, win->data->name, src_w);
-		src_w = ALIGN_DOWN(src_w, 4);
-	}
+	if (vop2->version == VOP_VERSION_RK3568 && drm_is_afbc(fb->modifier))
+		WARN_ON(src_w % 4);
 
 	act_info = (src_h - 1) << 16 | ((src_w - 1) & 0xffff);
 	dsp_info = (dsp_h - 1) << 16 | ((dsp_w - 1) & 0xffff);

You haven't replied to Andy's comment yet [0].

[0] https://lore.kernel.org/dri-devel/7b4e26ec.75f3.19a77276b53.Coremail.andyshrk@163.com/ (local)

Hello,

I addressed the follow-ups where it was clarified that the 4 pixel
limitation was RK3566/RK3568-only. I'm not going to bring back the
post-atomic_check modification for a fast path, but I'm open to
suggestions on how to do this differently.

One solution might be to modify the state with the ALIGN_DOWN stuff
in atomic_check instead, where userspace is then aware of the change
being done to its requested parameters. I'll need to double-check
whether this is in line with atomic modesetting's design.

Kind regards,
Nicolas Frattaroli

Okay, so I've asked internally, and atomic_check isn't allowed to
modify any of the parameters either. There's efforts [0] underway
to allow error codes to be more specific, so that userspace knows
which constraint is being violated. That would allow userspace
applications to react by either adjusting their size or turning
off AFBC in this case. Turning off AFBC seems more generally
applicable here, since it means it won't need to resize the plane
and it'll save more than enough memory bandwidth by not going
through the GPU.

On that note: Andy, I didn't find a weston-simple-egl test in the
Weston 14.0.2 or git test suite, and weston-simple-egl itself does
not tell me whether GPU compositing is being used or not. Do you
have more information on how to test for this? I'd like to know
for when we have the necessary functionality in place to make
userspace smart enough to pick the fast path again.

I think weston-simple-egl is part of the weston client. When you build
weston from source, you should obtain it. Just run `weston-simple-egl` 
after compile and install weston.

And I guess you're using Debian... The weston package there also ships
with a weston-simple-egl binary [2].

Yeah, I know there's a tool called that, but I'm specifically curious
about how to determine whether it's using GPU compositing or what I
presume is fixed-function compositing.

When I enable some more logging with

  weston -l log,drm-backend,gl-renderer

and also some kms debug messages with

  echo 4 > /sys/module/drm/parameters/debug

then I see weston outputting

[atomic] drmModeAtomicCommit
        [repaint] Using mixed state composition
        [repaint] view 0xaaab18c00c10 using renderer composition
        [repaint] view 0xaaab18b68f00 using renderer composition
        [repaint] view 0xaaab18c00ec0 using renderer composition

regardless of whether the size is 250x250 or fullscreen. With
250x250, I know we're failing the plane check, because I see

  [  776.160101] rockchip-drm display-subsystem: [drm:vop2_plane_atomic_check
                 [rockchipdrm]] AFBC source rectangles must be 4-pixel
                 aligned; is 250

on the console, but with fullscreen I don't see any errors from plane-check
as the src_w is now divisible by 4, yet it's also "using renderer composition"
for all views.

Same goes for using `weston-simple-dmabuf-egl` (which is 256x256) instead of
the fullscreen simple-egl.

So basically, I need to know where a change in behaviour is actually
observed.

[1]: https://gitlab.freedesktop.org/wayland/weston/-/blob/main/clients/simple-egl.c
[2]: https://packages.debian.org/sid/arm64/weston/filelist

quoted

In either case, I think adhering to the atomic API to ensure
artifact-free presentation is more important here than enabling
a fast-path on RK3568. I do think in most real-world use case
scenarios, the fallback won't degrade user experience, because
almost everything performance intensive I can think of (video
playback, games) will likely already use a plane geometry
where the width is divisible by 4. 800, 1024, 1280, 1600, 1920,
2560, 3840 are all divisible by 4, so a window or full-screen
playback of common content won't need to fall back to GPU
compositing.

I'll send a v2 to fix another instance of "eSmart" left in a
message, but beyond that I think we should be good.

Kind regards,
Nicolas Frattaroli

https://lore.kernel.org/dri-devel/20251009-atomic-v6-0-d209709cc3ba@intel.com/ (local) [0]