[PATCH 4/5] drm/nouveau/kms: cache the DP encoder after it has been attached
From: David R. Hedges via B4 Relay
Date: Tue Nov 03 2026 - 15:06:42 EST
From: "David R. Hedges" <linuxdev844@xxxxxxxxxxxxxxxx>
nouveau_connector_create() caches the connector's DP encoder in
nv_connector->dp_encoder using find_encoder(). On nv50+ it's called
from nv50_display_create() before nv50_sor_create() has created the
encoder and attached it to the connector, so possible_encoders is
still empty, find_encoder() returns NULL, and dp_encoder is never set.
Two things depend on it:
- nouveau_dp_link_check(), which the HPD worker calls on IRQ_HPD,
reports the link as fine without looking at it when there's no DP
encoder. Until commit 633716501c94 ("drm/nouveau/disp: add dp
train method") it looked the encoder up each time; since then, a
sink that reports link loss with IRQ_HPD hasn't been retrained.
- nouveau_connector_atomic_check() has never called
drm_dp_mst_root_conn_atomic_check() for MST-capable root
connectors.
Set dp_encoder in nv50_sor_create() right after the SOR is attached to
the connector, and drop the assignment that can't succeed. This also
covers eDP, whose SOR is a DCB_OUTPUT_DP encoder too. On a GA102 with
GSP-RM 570.144, an IRQ_HPD now leads to a read of the sink's link
status, where before it produced no AUX traffic at all.
This depends on "drm/nouveau/kms/nv50-: reject DP modesets the link
can't carry" and "drm/nouveau/dp: restart lost links with a modeset on
GSP-RM". Without them, enabling the link check would have nouveau
retrain active links in place on GSP-RM, or restart them with a mode
the link can no longer carry, either of which can hang the display
engine. The MST atomic check this enables hasn't been tested.
Fixes: 11d2738940eb ("drm/nouveau/kms: Cache DP encoders in nouveau_connector")
Fixes: 633716501c94 ("drm/nouveau/disp: add dp train method")
Link: https://gitlab.freedesktop.org/drm/nouveau/-/work_items/515
Signed-off-by: David R. Hedges <linuxdev844@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/nouveau/dispnv50/disp.c | 1 +
drivers/gpu/drm/nouveau/nouveau_connector.c | 2 --
2 files changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 7f55c016d846..583368914bf0 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -1941,6 +1941,7 @@ nv50_sor_create(struct nouveau_encoder *nv_encoder)
if (dcbe->type == DCB_OUTPUT_DP) {
mutex_init(&nv_encoder->dp.hpd_irq_lock);
+ nv_connector->dp_encoder = nv_encoder;
if (disp->disp->object.oclass < GF110_DISP) {
/* HW has no support for address-only
diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
index cae4e35c30aa..845f284f3a20 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -1573,8 +1573,6 @@ nouveau_connector_create(struct drm_device *dev, int index)
switch (type) {
case DRM_MODE_CONNECTOR_DisplayPort:
- nv_connector->dp_encoder = find_encoder(&nv_connector->base, DCB_OUTPUT_DP);
- fallthrough;
case DRM_MODE_CONNECTOR_eDP:
drm_dp_cec_register_connector(&nv_connector->aux, connector);
break;
--
2.55.0