On 2024-09-06 17:20, sunpeng.li@xxxxxxx wrote:
> From: Leo Li <sunpeng.li@xxxxxxx>
>
> [Why]
>
> drm_normalize_zpos will set the crtc_state->zpos_changed to 1 if any of
> it's assigned planes changes zpos, or is removed/added from it.
>
> To have amdgpu_dm request a plane reset on this is too broad. For
> example, if only the cursor plane was moved from one crtc to another,
> the crtc's zpos_changed will be set to true. But that does not mean that
> the underlying primary plane requires a reset.
>
> [How]
>
> Narrow it down so that only the plane that has a change in zpos will
> require a reset.
>
> As a future TODO, we can further optimize this by only requiring a reset
> on z-order change. Z-order is different from z-pos, since a zpos change
> doesn't necessarily mean the z-ordering changed, and DC should only
> require a reset if the z-ordering changed.
>
> For example, the following zpos update does not change z-ordering:
>
> Plane A: zpos 2 -> 3
> Plane B: zpos 1 -> 2
> => Plane A is still on top of plane B: no reset needed
>
> Whereas this one does change z-ordering:
>
> Plane A: zpos 2 -> 1
> Plane B: zpos 1 -> 2
> => Plane A changed from on top, to below plane B: reset needed
>
> Fixes: 38e0c3df6dbd ("drm/amd/display: Move PRIMARY plane zpos higher")
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3569
> Signed-off-by: Leo Li <sunpeng.li@xxxxxxx>
Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Harry
> ---
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 43bf8883ddc0f..a3edaf658ae00 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -10579,7 +10579,7 @@ static bool should_reset_plane(struct drm_atomic_state *state,
> * TODO: We can likely skip bandwidth validation if the only thing that
> * changed about the plane was it'z z-ordering.
> */
> - if (new_crtc_state->zpos_changed)
> + if (old_plane_state->normalized_zpos != new_plane_state->normalized_zpos)
> return true;
>
> if (drm_atomic_crtc_needs_modeset(new_crtc_state))
