+ Harry, Leo
On Mon, Jun 23, 2025 at 9:38 AM Christopher Snowhill <ch...@kode54.net> wrote:
>
> On Mon Jun 23, 2025 at 4:06 AM PDT, Christopher Snowhill wrote:
> > On Mon Jun 23, 2025 at 3:46 AM PDT, Christopher Snowhill wrote:
> >> On Fri Jun 20, 2025 at 3:10 AM PDT, Christopher Snowhill wrote:
> >>> Here's another alternative change, which may be more thorough. It does
> >>> seem to fix the issue, at least. The issue does indeed appear to be
> >>> no-op plane changes sent to the cursor plane.
> >>>
> >>> If anyone wants to propose style changes, and suggest a proper commit
> >>> message, if this is indeed a welcome fix for the problem, please let me
> >>> know.
> >>>
> >>> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c
> >>> b/drivers/gpu/drm/drm_atomic_uapi.c
> >>> index c2726af6698e..b741939698e8 100644
> >>> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> >>> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> >>> @@ -1087,17 +1087,22 @@ int drm_atomic_set_property(struct
> >>> drm_atomic_state *state,
> >>> }
> >>>
> >>> /* ask the driver if this non-primary plane is
> >>> supported */
> >>> - if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
> >>> - ret = -EINVAL;
> >>> + else if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
> >>> + ret = drm_atomic_plane_get_property(plane,
> >>> plane_state,
> >>> + prop,
> >>> &old_val);
> >>> +
> >>> + if (ret || old_val != prop_value) {
> >>> + ret = -EINVAL;
> >>>
> >>> - if (plane_funcs &&
> >>> plane_funcs->atomic_async_check)
> >>> - ret =
> >>> plane_funcs->atomic_async_check(plane, state, true);
> >>> + if (plane_funcs &&
> >>> plane_funcs->atomic_async_check)
> >>> + ret =
> >>> plane_funcs->atomic_async_check(plane, state, true);
> >>>
> >>> - if (ret) {
> >>> - drm_dbg_atomic(prop->dev,
> >>> - "[PLANE:%d:%s] does
> >>> not support async flips\n",
> >>> - obj->id, plane->name);
> >>> - break;
> >>> + if (ret) {
> >>> + drm_dbg_atomic(prop->dev,
> >>> + "[PLANE:%d:%s]
> >>> does not support async flips\n",
> >>> + obj->id,
> >>> plane->name);
> >>> + break;
> >>> + }
> >>> }
> >>> }
> >>> }
> >>
> >> Upon further testing and reflection, I have come to the conclusion that
> >> this is indeed best handled by a kernel fix, rather than breaking user
> >> space.
> >>
> >> I attempted to work around this in wlroots, adjusting 0.18, 0.19, and
> >> 0.20 git with similar patches. First I attempted to stash all the
> >> written properties for the atomic code, storing an initial value of all
> >> 0xFE so it was always likely to write the first time, and only setting a
> >> property if it changed from the last commit.
> >>
> >> This resulted in whole commits breaking for one or both framebuffers
> >> until I ctrl-alt-fx switched to a tty and back again, and this would
> >> work again temporarily.
> >>
> >> So I went back to the drawing board and only withheld seemingly
> >> duplicate plane properties. This "worked", until I attempted to play a
> >> game, and then it started glitching spectacularly, and not updating at
> >> all if the game was doing direct scanout and vrr.
> >>
> >> Clearly this is wrong.
> >>
> >> The wlroots library queues up properties for each commit. On every
> >> commit where the cursor is disabled, it queues up both fb_id=0 and
> >> crtc_id=0. Every commit. Is this wrong? Should it only be queueing up
> >> the disablement properties once? It also queues up the full plane and
> >> hotspot properties when enabled, even if the cursor doesn't change
> >> position or appearance.
> >
> > Probably should have CC'd the drm misc maintainers when I started poking
> > drm misc instead of amdgpu. Pity there isn't a list for that...
>
> I am a dumbass, I didn't notice get_maintainer.pl. Added more people,
> and the correct list. Not sure if I should remove amd-gfx, since this
> affects them, somewhat...
>
> However, the intention of this thread was to seek commentary on the
> situation as it is.
