diff --git a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
index 01864fe816a3..4723e0974647 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
+++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
@@ -2527,3 +2527,21 @@ bool dc_dmub_srv_panel_polarity_get_polarity(struct dc_dmub_srv *dc_dmub_srv, ui
 
 	return ret;
 }
+
+void dc_dmub_srv_hubbub_set_riommu_pctrl(const struct dc_context *ctx, uint32_t value)
+{
+	union dmub_rb_cmd cmd;
+
+	if (!(ctx->dce_version == DCN_VERSION_4_2 || ctx->dce_version == DCN_VERSION_4_2B))
+		return;
+
+	memset(&cmd, 0, sizeof(cmd));
+
+	cmd.dc_bls_dchvm_init.header.type = DMUB_CMD__DC_BLS;
+	cmd.dc_bls_dchvm_init.header.sub_type = DMUB_CMD__DC_BLS_DCHVM_INIT;
+	cmd.dc_bls_dchvm_init.header.payload_bytes = sizeof(struct dmub_cmd_dc_bls_dchvm_init_data);
+
+	cmd.dc_bls_dchvm_init.data.riommu_pctrl_val = value;
+
+	dc_wake_and_execute_dmub_cmd(ctx, &cmd, DM_DMUB_WAIT_TYPE_WAIT);
+}
diff --git a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.h b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.h
index ec5387aedf46..ab026847e38b 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.h
@@ -451,4 +451,16 @@ void dc_dmub_srv_panel_polarity_reset(struct dc_dmub_srv *dc_dmub_srv, uint8_t p
  */
 bool dc_dmub_srv_panel_polarity_get_polarity(struct dc_dmub_srv *dc_dmub_srv, uint8_t panel_inst, int32_t *polarity);
 
+/**
+ * dc_dmub_srv_hubbub_set_riommu_pctrl() - Program the RIOMMU PCTRL register via DMCUB.
+ *
+ * The RIOMMU PCTRL register (SMN address 0x16B0A100) controls the SDP port
+ * disconnection hysteresis between rIOMMU & DCHVM. It is not accessible from
+ * x86, so the write is offloaded to DMCUB.
+ *
+ * @ctx: dc context
+ * @value: value to program into the register (e.g. 0x20)
+ */
+void dc_dmub_srv_hubbub_set_riommu_pctrl(const struct dc_context *ctx, uint32_t value);
+
 #endif /* _DMUB_DC_SRV_H_ */
diff --git a/drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c b/drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c
index 5e5a7a74346d..53744b000f5d 100644
--- a/drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c
+++ b/drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c
@@ -31,6 +31,7 @@
 #include "dcn35_hubbub.h"
 #include "dm_services.h"
 #include "reg_helper.h"
+#include "dc_dmub_srv.h"
 
 
 #define CTX \
@@ -580,7 +581,13 @@ void dcn35_dchvm_init(struct hubbub *hubbub)
 
 		//Reflect the power status of DCHUBBUB
 		REG_UPDATE(DCHVM_RIOMMU_CTRL0, HOSTVM_POWERSTATUS, 1);
+		udelay(5);
+	}
 
+	// generically re-allow the DCHVM<->rIOMMU SDP port to disconnect after powerstatus=1
+	dc_dmub_srv_hubbub_set_riommu_pctrl(hubbub->ctx, 0x20);
+
+	if (riommu_active) {
 		//Start rIOMMU prefetching
 		REG_UPDATE(DCHVM_RIOMMU_CTRL0, HOSTVM_PREFETCH_REQ, 1);