[PATCH 1/2] drm/dp/mst: Sideband message transaction to power up/down nodes

[Dhinakaran Pandiyan]

The POWER_DOWN_PHY and POWER_UP_PHY sideband message transactions allow
the source to reqest any node in a mst path or a whole path to be
powered down or up. This allows drivers to target a specific sink in the
MST topology, an improvement over just power managing the imediate
downstream device. Secondly, since the request-reply protocol waits for an
ACK, we can be sure that a downstream sink has enough time to respond to a
power up/down request.

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 71 +++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |  1 +
 2 files changed, 72 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 41b492f99955..a0550e41c454 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -294,6 +294,12 @@ static void drm_dp_encode_sideband_req(struct drm_dp_sideband_msg_req_body *req,
 		memcpy(&buf[idx], req->u.i2c_write.bytes, req->u.i2c_write.num_bytes);
 		idx += req->u.i2c_write.num_bytes;
 		break;
+
+	case DP_POWER_DOWN_PHY:
+	case DP_POWER_UP_PHY:
+		buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
+		idx++;
+		break;
 	}
 	raw->cur_len = idx;
 }
@@ -538,6 +544,20 @@ static bool drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_r
 	return false;
 }
 
+
+static bool drm_dp_sideband_parse_power_updown_phy_ack(struct drm_dp_sideband_msg_rx *raw,
+						       struct drm_dp_sideband_msg_reply_body *repmsg)
+{
+	int idx = 1;
+	repmsg->u.port_number.port_number = (raw->msg[idx] >> 4) & 0xf;
+	idx++;
+	if (idx > raw->curlen) {
+		DRM_DEBUG_KMS("power up/down phy parse length fail %d %d\n", idx, raw->curlen);
+		return false;
+	}
+	return true;
+}
+
 static bool drm_dp_sideband_parse_reply(struct drm_dp_sideband_msg_rx *raw,
 					struct drm_dp_sideband_msg_reply_body *msg)
 {
@@ -567,6 +587,9 @@ static bool drm_dp_sideband_parse_reply(struct drm_dp_sideband_msg_rx *raw,
 		return drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
 	case DP_ALLOCATE_PAYLOAD:
 		return drm_dp_sideband_parse_allocate_payload_ack(raw, msg);
+	case DP_POWER_DOWN_PHY:
+	case DP_POWER_UP_PHY:
+		return drm_dp_sideband_parse_power_updown_phy_ack(raw, msg);
 	default:
 		DRM_ERROR("Got unknown reply 0x%02x\n", msg->req_type);
 		return false;
@@ -693,6 +716,22 @@ static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_n
 	return 0;
 }
 
+static int build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
+				  int port_num, bool power_up)
+{
+	struct drm_dp_sideband_msg_req_body req;
+
+	if (power_up)
+		req.req_type = DP_POWER_UP_PHY;
+	else
+		req.req_type = DP_POWER_DOWN_PHY;
+
+	req.u.port_num.port_number = port_num;
+	drm_dp_encode_sideband_req(&req, msg);
+	msg->path_msg = true;
+	return 0;
+}
+
 static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
 					struct drm_dp_vcpi *vcpi)
 {
@@ -1724,6 +1763,38 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 	return ret;
 }
 
+int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
+				 struct drm_dp_mst_port *port, bool power_up)
+{
+	struct drm_dp_sideband_msg_tx *txmsg;
+	int len, ret;
+
+	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
+	if (!txmsg)
+		return -ENOMEM;
+
+	port = drm_dp_get_validated_port_ref(mgr, port);
+	if (!port)
+		return -EINVAL;
+
+	txmsg->dst = port->parent;
+	len = build_power_updown_phy(txmsg, port->port_num, power_up);
+	drm_dp_queue_down_tx(mgr, txmsg);
+
+	ret = drm_dp_mst_wait_tx_reply(port->parent, txmsg);
+	if (ret > 0) {
+		if (txmsg->reply.reply_type == 1)
+			ret = -EINVAL;
+		else
+			ret = 0;
+	}
+	kfree(txmsg);
+	drm_dp_put_port(port);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_send_power_updown_phy);
+
 static int drm_dp_create_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
 				       int id,
 				       struct drm_dp_payload *payload)
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index d55abb75f29a..09893d81cd33 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -631,5 +631,6 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
 int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
 				     struct drm_dp_mst_topology_mgr *mgr,
 				     int slots);
+int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, bool power_up);
 
 #endif
-- 
2.11.0