drm/i915: Unlink NV12 planes earlier

unlink_nv12_plane() will clobber parts of the plane state
potentially already set up by plane_atomic_check(), so we
must make sure not to call the two in the wrong order.
The problem happens when a plane previously selected as
a Y plane is now configured as a normal plane by user space.
plane_atomic_check() will first compute the proper plane
state based on the userspace request, and unlink_nv12_plane()
later clears some of the state.

This used to work on account of unlink_nv12_plane() skipping
the state clearing based on the plane visibility. But I removed
that check, thinking it was an impossible situation. Now when
that situation happens unlink_nv12_plane() will just WARN
and proceed to clobber the state.

Rather than reverting to the old way of doing things, I think
it's more clear if we unlink the NV12 planes before we even
compute the new plane state.

Cc: stable@vger.kernel.org
Reported-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Closes: https://lore.kernel.org/intel-gfx/20260212004852.1920270-1-khaled.almahallawy@intel.com/
Tested-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Fixes: 6a01df2f1b2a ("drm/i915: Remove pointless visible check in unlink_nv12_plane()")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260316163953.12905-2-ville.syrjala@linux.intel.com
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
(cherry picked from commit 017ecd04985573eeeb0745fa2c23896fb22ee0cc)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_plane.c b/drivers/gpu/drm/i915/display/intel_plane.c
index e06a0618b4c6cd3b4d13752f604006b525118193..076b9b35648169af8ff4ec0e9917213e323514a2 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_plane.c
@@ -436,11 +436,16 @@ void intel_plane_copy_hw_state(struct intel_plane_state *plane_state,
                drm_framebuffer_get(plane_state->hw.fb);
 }
 
+static void unlink_nv12_plane(struct intel_crtc_state *crtc_state,
+                             struct intel_plane_state *plane_state);
+
 void intel_plane_set_invisible(struct intel_crtc_state *crtc_state,
                               struct intel_plane_state *plane_state)
 {
        struct intel_plane *plane = to_intel_plane(plane_state->uapi.plane);
 
+       unlink_nv12_plane(crtc_state, plane_state);
+
        crtc_state->active_planes &= ~BIT(plane->id);
        crtc_state->scaled_planes &= ~BIT(plane->id);
        crtc_state->nv12_planes &= ~BIT(plane->id);
@@ -1513,6 +1518,9 @@ static void unlink_nv12_plane(struct intel_crtc_state *crtc_state,
        struct intel_display *display = to_intel_display(plane_state);
        struct intel_plane *plane = to_intel_plane(plane_state->uapi.plane);
 
+       if (!plane_state->planar_linked_plane)
+               return;
+
        plane_state->planar_linked_plane = NULL;
 
        if (!plane_state->is_y_plane)
@@ -1550,8 +1558,7 @@ static int icl_check_nv12_planes(struct intel_atomic_state *state,
                if (plane->pipe != crtc->pipe)
                        continue;
 
-               if (plane_state->planar_linked_plane)
-                       unlink_nv12_plane(crtc_state, plane_state);
+               unlink_nv12_plane(crtc_state, plane_state);
        }
 
        if (!crtc_state->nv12_planes)