kernel/drm-dp-mst-error-handling-improvements.patch

From 52bd42038880354565bd5ca0bcc1d24b15136b0d Mon Sep 17 00:00:00 2001
From: Benjamin Gaignard <benjamin.gaignard@st.com>
Date: Wed, 5 Feb 2020 09:48:42 +0100
Subject: [PATCH 1/3] drm/dp_mst: Fix W=1 warnings

Fix the warnings that show up with W=1.
They are all about unused but set variables.
If functions returns are not used anymore make them void.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200205084842.5642-1-benjamin.gaignard@st.com
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 114 +++++++++++++++-----------
 1 file changed, 65 insertions(+), 49 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 415bd0770eab..95e08d908dd2 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1035,7 +1035,8 @@ static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
 	}
 }
 
-static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
+static void build_dpcd_write(struct drm_dp_sideband_msg_tx *msg,
+			     u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
@@ -1045,17 +1046,14 @@ static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32
 	req.u.dpcd_write.num_bytes = num_bytes;
 	req.u.dpcd_write.bytes = bytes;
 	drm_dp_encode_sideband_req(&req, msg);
-
-	return 0;
 }
 
-static int build_link_address(struct drm_dp_sideband_msg_tx *msg)
+static void build_link_address(struct drm_dp_sideband_msg_tx *msg)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
 	req.req_type = DP_LINK_ADDRESS;
 	drm_dp_encode_sideband_req(&req, msg);
-	return 0;
 }
 
 static int build_clear_payload_id_table(struct drm_dp_sideband_msg_tx *msg)
@@ -1067,7 +1065,8 @@ static int build_clear_payload_id_table(struct drm_dp_sideband_msg_tx *msg)
 	return 0;
 }
 
-static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
+static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg,
+				     int port_num)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
@@ -1078,10 +1077,11 @@ static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int por
 	return 0;
 }
 
-static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
-				  u8 vcpi, uint16_t pbn,
-				  u8 number_sdp_streams,
-				  u8 *sdp_stream_sink)
+static void build_allocate_payload(struct drm_dp_sideband_msg_tx *msg,
+				   int port_num,
+				   u8 vcpi, uint16_t pbn,
+				   u8 number_sdp_streams,
+				   u8 *sdp_stream_sink)
 {
 	struct drm_dp_sideband_msg_req_body req;
 	memset(&req, 0, sizeof(req));
@@ -1094,11 +1094,10 @@ static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_n
 		   number_sdp_streams);
 	drm_dp_encode_sideband_req(&req, msg);
 	msg->path_msg = true;
-	return 0;
 }
 
-static int build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
-				  int port_num, bool power_up)
+static void 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;
 
@@ -1110,7 +1109,6 @@ static int build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
 	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,
@@ -2073,29 +2071,24 @@ ssize_t drm_dp_mst_dpcd_write(struct drm_dp_aux *aux,
 				      offset, size, buffer);
 }
 
-static void drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)
+static int drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)
 {
-	int ret;
+	int ret = 0;
 
 	memcpy(mstb->guid, guid, 16);
 
 	if (!drm_dp_validate_guid(mstb->mgr, mstb->guid)) {
 		if (mstb->port_parent) {
-			ret = drm_dp_send_dpcd_write(
-					mstb->mgr,
-					mstb->port_parent,
-					DP_GUID,
-					16,
-					mstb->guid);
+			ret = drm_dp_send_dpcd_write(mstb->mgr,
+						     mstb->port_parent,
+						     DP_GUID, 16, mstb->guid);
 		} else {
-
-			ret = drm_dp_dpcd_write(
-					mstb->mgr->aux,
-					DP_GUID,
-					mstb->guid,
-					16);
+			ret = drm_dp_dpcd_write(mstb->mgr->aux,
+						DP_GUID, mstb->guid, 16);
 		}
 	}
+
+	return ret;
 }
 
 static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
@@ -2641,7 +2634,8 @@ static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
 	return false;
 }
 
-static int build_dpcd_read(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes)
+static void build_dpcd_read(struct drm_dp_sideband_msg_tx *msg,
+			    u8 port_num, u32 offset, u8 num_bytes)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
@@ -2650,8 +2644,6 @@ static int build_dpcd_read(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32
 	req.u.dpcd_read.dpcd_address = offset;
 	req.u.dpcd_read.num_bytes = num_bytes;
 	drm_dp_encode_sideband_req(&req, msg);
-
-	return 0;
 }
 
 static int drm_dp_send_sideband_msg(struct drm_dp_mst_topology_mgr *mgr,
@@ -2877,7 +2869,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_link_address_ack_reply *reply;
 	struct drm_dp_mst_port *port, *tmp;
-	int i, len, ret, port_mask = 0;
+	int i, ret, port_mask = 0;
 	bool changed = false;
 
 	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
@@ -2885,7 +2877,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 		return -ENOMEM;
 
 	txmsg->dst = mstb;
-	len = build_link_address(txmsg);
+	build_link_address(txmsg);
 
 	mstb->link_address_sent = true;
 	drm_dp_queue_down_tx(mgr, txmsg);
@@ -2906,7 +2898,9 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 	DRM_DEBUG_KMS("link address reply: %d\n", reply->nports);
 	drm_dp_dump_link_address(reply);
 
-	drm_dp_check_mstb_guid(mstb, reply->guid);
+	ret = drm_dp_check_mstb_guid(mstb, reply->guid);
+	if (ret)
+		goto out;
 
 	for (i = 0; i < reply->nports; i++) {
 		port_mask |= BIT(reply->ports[i].port_number);
@@ -2947,14 +2941,14 @@ void drm_dp_send_clear_payload_id_table(struct drm_dp_mst_topology_mgr *mgr,
 					struct drm_dp_mst_branch *mstb)
 {
 	struct drm_dp_sideband_msg_tx *txmsg;
-	int len, ret;
+	int ret;
 
 	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
 	if (!txmsg)
 		return;
 
 	txmsg->dst = mstb;
-	len = build_clear_payload_id_table(txmsg);
+	build_clear_payload_id_table(txmsg);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -2972,7 +2966,6 @@ drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 {
 	struct drm_dp_enum_path_resources_ack_reply *path_res;
 	struct drm_dp_sideband_msg_tx *txmsg;
-	int len;
 	int ret;
 
 	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
@@ -2980,7 +2973,7 @@ drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 		return -ENOMEM;
 
 	txmsg->dst = mstb;
-	len = build_enum_path_resources(txmsg, port->port_num);
+	build_enum_path_resources(txmsg, port->port_num);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -3073,7 +3066,7 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 {
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
-	int len, ret, port_num;
+	int ret, port_num;
 	u8 sinks[DRM_DP_MAX_SDP_STREAMS];
 	int i;
 
@@ -3098,9 +3091,9 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 		sinks[i] = i;
 
 	txmsg->dst = mstb;
-	len = build_allocate_payload(txmsg, port_num,
-				     id,
-				     pbn, port->num_sdp_streams, sinks);
+	build_allocate_payload(txmsg, port_num,
+			       id,
+			       pbn, port->num_sdp_streams, sinks);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -3129,7 +3122,7 @@ 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;
+	int ret;
 
 	port = drm_dp_mst_topology_get_port_validated(mgr, port);
 	if (!port)
@@ -3142,7 +3135,7 @@ int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
 	}
 
 	txmsg->dst = port->parent;
-	len = build_power_updown_phy(txmsg, port->port_num, power_up);
+	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);
@@ -3364,7 +3357,6 @@ static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
 				 struct drm_dp_mst_port *port,
 				 int offset, int size, u8 *bytes)
 {
-	int len;
 	int ret = 0;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
@@ -3379,7 +3371,7 @@ static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
 		goto fail_put;
 	}
 
-	len = build_dpcd_read(txmsg, port->port_num, offset, size);
+	build_dpcd_read(txmsg, port->port_num, offset, size);
 	txmsg->dst = port->parent;
 
 	drm_dp_queue_down_tx(mgr, txmsg);
@@ -3417,7 +3409,6 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
 				  struct drm_dp_mst_port *port,
 				  int offset, int size, u8 *bytes)
 {
-	int len;
 	int ret;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
@@ -3432,7 +3423,7 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
 		goto fail_put;
 	}
 
-	len = build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
+	build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
 	txmsg->dst = mstb;
 
 	drm_dp_queue_down_tx(mgr, txmsg);
@@ -3682,7 +3673,12 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
 		DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
 		goto out_fail;
 	}
-	drm_dp_check_mstb_guid(mgr->mst_primary, guid);
+
+	ret = drm_dp_check_mstb_guid(mgr->mst_primary, guid);
+	if (ret) {
+		DRM_DEBUG_KMS("check mstb failed - undocked during suspend?\n");
+		goto out_fail;
+	}
 
 	/*
 	 * For the final step of resuming the topology, we need to bring the
@@ -4625,15 +4621,34 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 		int ret;
 
 		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE);
+		if (ret) {
+			seq_printf(m, "dpcd read failed\n");
+			goto out;
+		}
 		seq_printf(m, "dpcd: %*ph\n", DP_RECEIVER_CAP_SIZE, buf);
+
 		ret = drm_dp_dpcd_read(mgr->aux, DP_FAUX_CAP, buf, 2);
+		if (ret) {
+			seq_printf(m, "faux/mst read failed\n");
+			goto out;
+		}
 		seq_printf(m, "faux/mst: %*ph\n", 2, buf);
+
 		ret = drm_dp_dpcd_read(mgr->aux, DP_MSTM_CTRL, buf, 1);
+		if (ret) {
+			seq_printf(m, "mst ctrl read failed\n");
+			goto out;
+		}
 		seq_printf(m, "mst ctrl: %*ph\n", 1, buf);
 
 		/* dump the standard OUI branch header */
 		ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_BRANCH_OUI_HEADER_SIZE);
+		if (ret) {
+			seq_printf(m, "branch oui read failed\n");
+			goto out;
+		}
 		seq_printf(m, "branch oui: %*phN devid: ", 3, buf);
+
 		for (i = 0x3; i < 0x8 && buf[i]; i++)
 			seq_printf(m, "%c", buf[i]);
 		seq_printf(m, " revision: hw: %x.%x sw: %x.%x\n",
@@ -4642,6 +4657,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 			seq_printf(m, "payload table: %*ph\n", DP_PAYLOAD_TABLE_SIZE, buf);
 	}
 
+out:
 	mutex_unlock(&mgr->lock);
 
 }
-- 
2.25.1

From 9004e704af8486da3dcbde0fb35a2a309152a5c3 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Fri, 6 Mar 2020 18:49:21 -0500
Subject: [PATCH 2/3] drm/dp_mst: Make drm_dp_mst_dpcd_write() consistent with
 drm_dp_dpcd_write()

Noticed this while having some problems with hubs sometimes not being
detected on the first plug. Every single dpcd read or write function
returns the number of bytes transferred on success or a negative error
code, except apparently for drm_dp_mst_dpcd_write() - which returns 0 on
success.

There's not really any good reason for this difference that I can tell,
and having the two functions give differing behavior means that
drm_dp_dpcd_write() will end up returning 0 on success for MST devices,
but the number of bytes transferred for everything else.

So, fix that and update the kernel doc.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 2f221a5efed4 ("drm/dp_mst: Add MST support to DP DPCD R/W functions")
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Mikita Lipski <mikita.lipski@amd.com>
Cc: Sean Paul <sean@poorly.run>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 95e08d908dd2..2dc1c0ba456b 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2059,7 +2059,7 @@ ssize_t drm_dp_mst_dpcd_read(struct drm_dp_aux *aux,
  * sideband messaging as drm_dp_dpcd_write() does for local
  * devices via actual AUX CH.
  *
- * Return: 0 on success, negative error code on failure.
+ * Return: number of bytes written on success, negative error code on failure.
  */
 ssize_t drm_dp_mst_dpcd_write(struct drm_dp_aux *aux,
 			      unsigned int offset, void *buffer, size_t size)
@@ -3429,12 +3429,9 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
 	drm_dp_queue_down_tx(mgr, txmsg);
 
 	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
-	if (ret > 0) {
-		if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
-			ret = -EIO;
-		else
-			ret = 0;
-	}
+	if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
+		ret = -EIO;
+
 	kfree(txmsg);
 fail_put:
 	drm_dp_mst_topology_put_mstb(mstb);
-- 
2.25.1

From ff18e1a7ef709cdd3dcbf7b4ae2b37e1c6695289 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Fri, 6 Mar 2020 18:49:22 -0500
Subject: [PATCH 3/3] drm/dp_mst: Fix drm_dp_check_mstb_guid() return code

We actually expect this to return a 0 on success, or negative error code
on failure. In order to do that, we check whether or not we managed to
write the whole GUID and then return 0 if so, otherwise return a
negative error code. Also, let's add an error message here so it's a
little more obvious when this fails in the middle of a link address
probe.

This should fix issues with certain MST hubs seemingly stopping for no
reason in the middle of the link address probe process.

Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 2dc1c0ba456b..d0e5993b0622 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2088,7 +2088,10 @@ static int drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)
 		}
 	}
 
-	return ret;
+	if (ret < 16 && ret > 0)
+		return -EPROTO;
+
+	return ret == 16 ? 0 : ret;
 }
 
 static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
@@ -2899,8 +2902,14 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 	drm_dp_dump_link_address(reply);
 
 	ret = drm_dp_check_mstb_guid(mstb, reply->guid);
-	if (ret)
+	if (ret) {
+		char buf[64];
+
+		drm_dp_mst_rad_to_str(mstb->rad, mstb->lct, buf, sizeof(buf));
+		DRM_ERROR("GUID check on %s failed: %d\n",
+			  buf, ret);
 		goto out;
+	}
 
 	for (i = 0; i < reply->nports; i++) {
 		port_mask |= BIT(reply->ports[i].port_number);
-- 
2.25.1