[PATCH v2 14/17] drm/display/dp_mst: Factor out a helper to reset the payload table

[Imre Deak <imre.deak@xxxxxxxxx>]

A follow-up patch adds a workaround for a payload allocation problem in
a DELL monitor. For this the driver needs to reset the payload table in
the monitor's MST hub, factor out a helper to do this.

While at it use DP_PAYLOAD_TABLE_SIZE in the reset command, instead of
open coding it.

Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 8 +++++++-
 include/drm/display/drm_dp_mst_helper.h       | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index d0e929df7d088..eb170389cf9bc 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3429,6 +3429,12 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
 }
 EXPORT_SYMBOL(drm_dp_add_payload_part2);
 
+int drm_dp_mst_reset_payload_table(struct drm_dp_mst_topology_mgr *mgr)
+{
+	return drm_dp_dpcd_write_payload(mgr, 0, 0, DP_PAYLOAD_TABLE_SIZE - 1);
+}
+EXPORT_SYMBOL(drm_dp_mst_reset_payload_table);
+
 /**
  * drm_dp_mst_has_payload_alloc_errors - Query for payload allocation errors
  * @mst_state: The MST atomic state
@@ -3699,7 +3705,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 			goto out_unlock;
 
 		/* Write reset payload */
-		drm_dp_dpcd_write_payload(mgr, 0, 0, 0x3f);
+		drm_dp_mst_reset_payload_table(mgr);
 
 		queue_work(system_long_wq, &mgr->work);
 
diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
index bb7c595096fed..2d15399df2950 100644
--- a/include/drm/display/drm_dp_mst_helper.h
+++ b/include/drm/display/drm_dp_mst_helper.h
@@ -845,6 +845,7 @@ void drm_dp_remove_payload(struct drm_dp_mst_topology_mgr *mgr,
 			   struct drm_dp_mst_topology_state *mst_state,
 			   const struct drm_dp_mst_atomic_payload *old_payload,
 			   struct drm_dp_mst_atomic_payload *new_payload);
+int drm_dp_mst_reset_payload_table(struct drm_dp_mst_topology_mgr *mgr);
 bool drm_dp_mst_has_payload_alloc_errors(const struct drm_dp_mst_topology_state *mst_state);
 int drm_dp_mst_payload_vchannel(const struct drm_dp_mst_topology_state *mst_state,
 				const struct drm_dp_mst_atomic_payload *payload);
-- 
2.37.1