[PATCH 3/3] drm/mediatek: mtk_crtc: Pick the connector route on every CRTC enable

[zoan37 <agentzoan@gmail.com>]

mtk_crtc_update_output() only picks the output component of a CRTC
with connector routes when connectors_changed is set in the commit that
enables the CRTC. But connectors_changed only says that the connectors
changed in that commit, not since the CRTC was last enabled. A connector
can be attached to (or moved to) the CRTC while it is inactive, and the
later commit that only sets ACTIVE then has active_changed but not
connectors_changed:

- If the CRTC had never been enabled, the route slot is still NULL and
  mtk_crtc_ddp_hw_init() dereferences it (mtk_ddp_comp_clk_enable()
  and so on).
- If the CRTC was driven through another route before, e.g. a CRTC
  shared by an HDMI bridge on DSI and a DisplayPort output that is
  switched off (DPMS) while the monitor moves from one to the other,
  the pipeline is set up for the old output.

update_output() only runs from atomic_enable and the lookup is a short
loop over the routes, so do it on every enable.

Fixes: 01389b324c97 ("drm/mediatek: Add connector dynamic selection capability")
Assisted-by: LLM
Signed-off-by: zoan37 <agentzoan@gmail.com>
---

Notes:
    Testing: found by reading the code. The same change runs on the MT8189
    Chromebook described in patch 1, where one routed CRTC drives either
    HDMI or USB-C DisplayPort: DPMS off/on and suspend/resume with a DP
    monitor attached come back. The sequence that fails without it
    (connector attached or swapped while the CRTC is inactive, then only
    ACTIVE set) was not reproduced on purpose. Compile-tested (W=1) on
    next-20261008.

 drivers/gpu/drm/mediatek/mtk_crtc.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
index 704931b369b6..0bfd17f68282 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
@@ -695,9 +695,6 @@ static void mtk_crtc_update_output(struct drm_crtc *crtc,
 	struct mtk_drm_private *priv;
 	unsigned int encoder_mask = crtc_state->encoder_mask;
 
-	if (!crtc_state->connectors_changed)
-		return;
-
 	if (!mtk_crtc->num_conn_routes)
 		return;
 
-- 
2.43.0