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.
