[PATCH v7 16/20] drm/nouveau: Grab payload lock in nv50_msto_payload()

[Lyude Paul]

Going through the currently programmed payloads isn't safe without
holding mgr->payload_lock, so actually do that and warn if anyone tries
calling nv50_msto_payload() in the future without grabbing the right
locks.

Signed-off-by: Lyude Paul <lyude at redhat.com>
Reviewed-By: Ben Skeggs <bskeggs at redhat.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: David Airlie <airlied at redhat.com>
Cc: Jerry Zuo <Jerry.Zuo at amd.com>
Cc: Harry Wentland <harry.wentland at amd.com>
Cc: Juston Li <juston.li at intel.com>
---
 drivers/gpu/drm/nouveau/dispnv50/disp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 6f8a54e81727..8044ebba56a4 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -679,6 +679,8 @@ nv50_msto_payload(struct nv50_msto *msto)
 	struct nv50_mstm *mstm = mstc->mstm;
 	int vcpi = mstc->port->vcpi.vcpi, i;
 
+	WARN_ON(!mutex_is_locked(&mstm->mgr.payload_lock));
+
 	NV_ATOMIC(drm, "%s: vcpi %d\n", msto->encoder.name, vcpi);
 	for (i = 0; i < mstm->mgr.max_payloads; i++) {
 		struct drm_dp_payload *payload = &mstm->mgr.payloads[i];
@@ -732,6 +734,8 @@ nv50_msto_prepare(struct nv50_msto *msto)
 			       (0x0100 << msto->head->base.index),
 	};
 
+	mutex_lock(&mstm->mgr.payload_lock);
+
 	NV_ATOMIC(drm, "%s: msto prepare\n", msto->encoder.name);
 	if (mstc->port->vcpi.vcpi > 0) {
 		struct drm_dp_payload *payload = nv50_msto_payload(msto);
@@ -747,7 +751,9 @@ nv50_msto_prepare(struct nv50_msto *msto)
 		  msto->encoder.name, msto->head->base.base.name,
 		  args.vcpi.start_slot, args.vcpi.num_slots,
 		  args.vcpi.pbn, args.vcpi.aligned_pbn);
+
 	nvif_mthd(&drm->display->disp.object, 0, &args, sizeof(args));
+	mutex_unlock(&mstm->mgr.payload_lock);
 }
 
 static int
-- 
2.20.1