From 57442e15eba936153f8753187c25af8f9991b53a Mon Sep 17 00:00:00 2001
From: Sean Paul <seanpaul@chromium.org>
Date: Thu, 13 Feb 2020 16:15:18 -0500
Subject: drm/mst: Separate sideband packet header parsing from message
Git-commit: 21a729d00776799c553b1cf45cb798c852ead660
Patch-mainline: v5.8-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
 building

In preparation of per-branch device down message handling, separate
header parsing from message building. This will allow us to peek at
figure out which branch device the message is from before starting to
parse the message contents.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Wayne Lin <waynelin@amd.com>
[seanpaul s/drm_dp_sideband_msg_build/drm_dp_sideband_msg_set_header/]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200213211523.156998-2-sean@poorly.run
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 102 ++++++++++++++------------
 1 file changed, 57 insertions(+), 45 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 35b62c5d18b4..7ffd15a38a7a 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -687,51 +687,45 @@ static void drm_dp_encode_sideband_reply(struct drm_dp_sideband_msg_reply_body *
 	raw->cur_len = idx;
 }
 
-/* this adds a chunk of msg to the builder to get the final msg */
-static bool drm_dp_sideband_msg_build(struct drm_dp_sideband_msg_rx *msg,
-				      u8 *replybuf, u8 replybuflen, bool hdr)
+static int drm_dp_sideband_msg_set_header(struct drm_dp_sideband_msg_rx *msg,
+					  struct drm_dp_sideband_msg_hdr *hdr,
+					  u8 hdrlen)
 {
-	int ret;
-	u8 crc4;
+	/*
+	 * ignore out-of-order messages or messages that are part of a
+	 * failed transaction
+	 */
+	if (!hdr->somt && !msg->have_somt)
+		return false;
 
-	if (hdr) {
-		u8 hdrlen;
-		struct drm_dp_sideband_msg_hdr recv_hdr;
-		ret = drm_dp_decode_sideband_msg_hdr(&recv_hdr, replybuf, replybuflen, &hdrlen);
-		if (ret == false) {
-			print_hex_dump(KERN_DEBUG, "failed hdr", DUMP_PREFIX_NONE, 16, 1, replybuf, replybuflen, false);
-			return false;
-		}
+	/* get length contained in this portion */
+	msg->curchunk_idx = 0;
+	msg->curchunk_len = hdr->msg_len;
+	msg->curchunk_hdrlen = hdrlen;
 
-		/*
-		 * ignore out-of-order messages or messages that are part of a
-		 * failed transaction
-		 */
-		if (!recv_hdr.somt && !msg->have_somt)
-			return false;
+	/* we have already gotten an somt - don't bother parsing */
+	if (hdr->somt && msg->have_somt)
+		return false;
 
-		/* get length contained in this portion */
-		msg->curchunk_len = recv_hdr.msg_len;
-		msg->curchunk_hdrlen = hdrlen;
+	if (hdr->somt) {
+		memcpy(&msg->initial_hdr, hdr,
+		       sizeof(struct drm_dp_sideband_msg_hdr));
+		msg->have_somt = true;
+	}
+	if (hdr->eomt)
+		msg->have_eomt = true;
 
-		/* we have already gotten an somt - don't bother parsing */
-		if (recv_hdr.somt && msg->have_somt)
-			return false;
+	return true;
+}
 
-		if (recv_hdr.somt) {
-			memcpy(&msg->initial_hdr, &recv_hdr, sizeof(struct drm_dp_sideband_msg_hdr));
-			msg->have_somt = true;
-		}
-		if (recv_hdr.eomt)
-			msg->have_eomt = true;
+/* this adds a chunk of msg to the builder to get the final msg */
+static bool drm_dp_sideband_append_payload(struct drm_dp_sideband_msg_rx *msg,
+					   u8 *replybuf, u8 replybuflen)
+{
+	u8 crc4;
 
-		/* copy the bytes for the remainder of this header chunk */
-		msg->curchunk_idx = min(msg->curchunk_len, (u8)(replybuflen - hdrlen));
-		memcpy(&msg->chunk[0], replybuf + hdrlen, msg->curchunk_idx);
-	} else {
-		memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
-		msg->curchunk_idx += replybuflen;
-	}
+	memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
+	msg->curchunk_idx += replybuflen;
 
 	if (msg->curchunk_idx >= msg->curchunk_len) {
 		/* do CRC */
@@ -3713,25 +3707,43 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
 	u8 replyblock[32];
 	int replylen, curreply;
 	int ret;
+	u8 hdrlen;
+	struct drm_dp_sideband_msg_hdr hdr;
 	struct drm_dp_sideband_msg_rx *msg;
-	int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE;
+	int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE :
+			   DP_SIDEBAND_MSG_DOWN_REP_BASE;
+
 	msg = up ? &mgr->up_req_recv : &mgr->down_rep_recv;
 
 	len = min(mgr->max_dpcd_transaction_bytes, 16);
-	ret = drm_dp_dpcd_read(mgr->aux, basereg,
-			       replyblock, len);
+	ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len);
 	if (ret != len) {
 		DRM_DEBUG_KMS("failed to read DPCD down rep %d %d\n", len, ret);
 		return false;
 	}
-	ret = drm_dp_sideband_msg_build(msg, replyblock, len, true);
+
+	ret = drm_dp_decode_sideband_msg_hdr(&hdr, replyblock, len, &hdrlen);
+	if (ret == false) {
+		print_hex_dump(KERN_DEBUG, "failed hdr", DUMP_PREFIX_NONE, 16,
+			       1, replyblock, len, false);
+		DRM_DEBUG_KMS("ERROR: failed header\n");
+		return false;
+	}
+
+	if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) {
+		DRM_DEBUG_KMS("sideband msg set header failed %d\n",
+			      replyblock[0]);
+		return false;
+	}
+
+	replylen = min(msg->curchunk_len, (u8)(len - hdrlen));
+	ret = drm_dp_sideband_append_payload(msg, replyblock + hdrlen, replylen);
 	if (!ret) {
 		DRM_DEBUG_KMS("sideband msg build failed %d\n", replyblock[0]);
 		return false;
 	}
-	replylen = msg->curchunk_len + msg->curchunk_hdrlen;
 
-	replylen -= len;
+	replylen = msg->curchunk_len + msg->curchunk_hdrlen - len;
 	curreply = len;
 	while (replylen > 0) {
 		len = min3(replylen, mgr->max_dpcd_transaction_bytes, 16);
@@ -3743,7 +3755,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
 			return false;
 		}
 
-		ret = drm_dp_sideband_msg_build(msg, replyblock, len, false);
+		ret = drm_dp_sideband_append_payload(msg, replyblock, len);
 		if (!ret) {
 			DRM_DEBUG_KMS("failed to build sideband msg\n");
 			return false;
-- 
2.28.0