drm/mst: Support simultaneous down replies

Currently we have one down reply message servicing the mst manager, so
we need to serialize all tx msgs to ensure we only have one message in
flight at a time. For obvious reasons this is suboptimal (but less
suboptimal than the free-for-all we had before serialization).

This patch removes the single down_rep_recv message from manager and
adds 2 replies in the branch structure. The 2 replies mirrors the tx_slots
which we use to rate-limit outgoing messages and correspond to seqno in
the packet headers.

Cc: Wayne Lin <Wayne.Lin@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Wayne Lin <waynelin@amd.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200213211523.156998-3-sean@poorly.run

1 files changed, 30 insertions, 29 deletions

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 9a1e8ba4f839..cff135070535 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -160,6 +160,31 @@ struct drm_dp_mst_port {
 	bool fec_capable;
 };
 
+/* sideband msg header - not bit struct */
+struct drm_dp_sideband_msg_hdr {
+	u8 lct;
+	u8 lcr;
+	u8 rad[8];
+	bool broadcast;
+	bool path_msg;
+	u8 msg_len;
+	bool somt;
+	bool eomt;
+	bool seqno;
+};
+
+struct drm_dp_sideband_msg_rx {
+	u8 chunk[48];
+	u8 msg[256];
+	u8 curchunk_len;
+	u8 curchunk_idx; /* chunk we are parsing now */
+	u8 curchunk_hdrlen;
+	u8 curlen; /* total length of the msg */
+	bool have_somt;
+	bool have_eomt;
+	struct drm_dp_sideband_msg_hdr initial_hdr;
+};
+
 /**
  * struct drm_dp_mst_branch - MST branch device.
  * @rad: Relative Address to talk to this branch device.
@@ -232,24 +257,16 @@ struct drm_dp_mst_branch {
 	int last_seqno;
 	bool link_address_sent;
 
+	/**
+	 * @down_rep_recv: Message receiver state for down replies.
+	 */
+	struct drm_dp_sideband_msg_rx down_rep_recv[2];
+
 	/* global unique identifier to identify branch devices */
 	u8 guid[16];
 };
 
 
-/* sideband msg header - not bit struct */
-struct drm_dp_sideband_msg_hdr {
-	u8 lct;
-	u8 lcr;
-	u8 rad[8];
-	bool broadcast;
-	bool path_msg;
-	u8 msg_len;
-	bool somt;
-	bool eomt;
-	bool seqno;
-};
-
 struct drm_dp_nak_reply {
 	u8 guid[16];
 	u8 reason;
@@ -306,18 +323,6 @@ struct drm_dp_remote_i2c_write_ack_reply {
 };
 
 
-struct drm_dp_sideband_msg_rx {
-	u8 chunk[48];
-	u8 msg[256];
-	u8 curchunk_len;
-	u8 curchunk_idx; /* chunk we are parsing now */
-	u8 curchunk_hdrlen;
-	u8 curlen; /* total length of the msg */
-	bool have_somt;
-	bool have_eomt;
-	struct drm_dp_sideband_msg_hdr initial_hdr;
-};
-
 #define DRM_DP_MAX_SDP_STREAMS 16
 struct drm_dp_allocate_payload {
 	u8 port_number;
@@ -556,10 +561,6 @@ struct drm_dp_mst_topology_mgr {
 	int conn_base_id;
 
 	/**
-	 * @down_rep_recv: Message receiver state for down replies.
-	 */
-	struct drm_dp_sideband_msg_rx down_rep_recv;
-	/**
 	 * @up_req_recv: Message receiver state for up requests.
 	 */
 	struct drm_dp_sideband_msg_rx up_req_recv;