[PATCH v2 3/6] drm/nouveau/kms/nv50-: Stop using nv_encoder->crtc in nv50_sor_atomic_disable()

[Lyude Paul <lyude@redhat.com>]

This is a leftover CRTC bookkeeping variable from the pre-atomic days.
While it works in most situations, it's prone to breaking - as pointed out
by Marek Czernohous.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reported-by: Marek Czernohous <mczernohous@gmail.com>
Fixes: f575f2bdb6c3 ("drm/nouveau/kms/nv50-: Remove (nv_encoder->crtc) checks in ->disable callbacks")
Cc: <stable@vger.kernel.org> # v5.12+
---
 drivers/gpu/drm/nouveau/dispnv50/disp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 152361f7feb42..f19820dc055ae 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -459,7 +459,7 @@ nv50_outp_get_old_connector(struct drm_atomic_commit *state, struct nouveau_enco
 	return NULL;
 }
 
-static struct nouveau_crtc * __maybe_unused
+static struct nouveau_crtc *
 nv50_outp_get_old_crtc(const struct drm_atomic_commit *state, const struct nouveau_encoder *outp)
 {
 	struct drm_crtc *crtc;
@@ -1606,12 +1606,18 @@ static void
 nv50_sor_atomic_disable(struct drm_encoder *encoder, struct drm_atomic_commit *state)
 {
 	struct nouveau_encoder *nv_encoder = nouveau_encoder(encoder);
-	struct nv50_head *head = nv50_head(nv_encoder->crtc);
+	struct nouveau_crtc *nv_crtc;
+	struct nv50_head *head;
 
 #ifdef CONFIG_DRM_NOUVEAU_BACKLIGHT
 	nv50_sor_atomic_disable_backlight(nouveau_drm(state->dev), nv_encoder, state);
 #endif
 
+	nv_crtc = nv50_outp_get_old_crtc(state, nv_encoder);
+	if (drm_WARN_ON(state->dev, !nv_crtc))
+		return;
+	head = nv50_head(&nv_crtc->base);
+
 	if (nv_encoder->dcb->type == DCB_OUTPUT_TMDS && nv_encoder->hdmi.enabled) {
 		nvif_outp_hdmi(&nv_encoder->outp, head->base.index,
 			       false, 0, 0, 0, false, false, false);
-- 
2.55.0