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Subject[PATCH 5.2 139/143] drm/i915: Do not create a new max_bpc prop for MST connectors
Date
[ Upstream commit 1b9bd09630d4db4827cc04d358a41a16a6bc2cb0 ]

We're not allowed to create new properties after device registration
so for MST connectors we need to either create the max_bpc property
earlier, or we reuse one we already have. Let's do the latter apporach
since the corresponding SST connector already has the prop and its
min/max are correct also for the MST connector.

The problem was highlighted by commit 4f5368b5541a ("drm/kms:
Catch mode_object lifetime errors") which results in the following
spew:
[ 1330.878941] WARNING: CPU: 2 PID: 1554 at drivers/gpu/drm/drm_mode_object.c:45 __drm_mode_object_add+0xa0/0xb0 [drm]
...
[ 1330.879008] Call Trace:
[ 1330.879023] drm_property_create+0xba/0x180 [drm]
[ 1330.879036] drm_property_create_range+0x15/0x30 [drm]
[ 1330.879048] drm_connector_attach_max_bpc_property+0x62/0x80 [drm]
[ 1330.879086] intel_dp_add_mst_connector+0x11f/0x140 [i915]
[ 1330.879094] drm_dp_add_port.isra.20+0x20b/0x440 [drm_kms_helper]
...

Cc: stable@vger.kernel.org
Cc: Lyude Paul <lyude@redhat.com>
Cc: sunpeng.li@amd.com
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>
Fixes: 5ca0ef8a56b8 ("drm/i915: Add max_bpc property for DP MST")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190820161657.9658-1-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/i915/intel_dp_mst.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 8839eaea83715..d89120dcac67d 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -535,7 +535,15 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo

intel_attach_force_audio_property(connector);
intel_attach_broadcast_rgb_property(connector);
- drm_connector_attach_max_bpc_property(connector, 6, 12);
+
+ /*
+ * Reuse the prop from the SST connector because we're
+ * not allowed to create new props after device registration.
+ */
+ connector->max_bpc_property =
+ intel_dp->attached_connector->base.max_bpc_property;
+ if (connector->max_bpc_property)
+ drm_connector_attach_max_bpc_property(connector, 6, 12);

return connector;

--
2.20.1


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