thunderbolt: Discover preboot PCIe paths the boot firmware established

In Apple Macs the boot firmware (EFI) connects all devices automatically
when the system is started, before it hands over to the OS. Instead of
ignoring we discover all those PCIe tunnels and record them using our
internal structures, just like we do when a device is connected after
the OS is already up.

By doing this we can properly tear down tunnels when devices are
disconnected. Also this allows us to resume the existing tunnels after
system suspend/resume cycle.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 182 insertions, 22 deletions

diff --git a/drivers/thunderbolt/path.c b/drivers/thunderbolt/path.c
index a7cdac7f6808..670a12e60d66 100644
--- a/drivers/thunderbolt/path.c
+++ b/drivers/thunderbolt/path.c
@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Thunderbolt Cactus Ridge driver - path/tunnel functionality
+ * Thunderbolt driver - path/tunnel functionality
  *
  * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ * Copyright (C) 2019, Intel Corporation
  */
 
 #include <linux/slab.h>
@@ -12,7 +13,6 @@
 
 #include "tb.h"
 
-
 static void tb_dump_hop(struct tb_port *port, struct tb_regs_hop *hop)
 {
 	tb_port_dbg(port, " Hop through port %d to hop %d (%s)\n",
@@ -30,6 +30,182 @@ static void tb_dump_hop(struct tb_port *port, struct tb_regs_hop *hop)
 		    hop->unknown1, hop->unknown2, hop->unknown3);
 }
 
+static struct tb_port *tb_path_find_dst_port(struct tb_port *src, int src_hopid,
+					     int dst_hopid)
+{
+	struct tb_port *port, *out_port = NULL;
+	struct tb_regs_hop hop;
+	struct tb_switch *sw;
+	int i, ret, hopid;
+
+	hopid = src_hopid;
+	port = src;
+
+	for (i = 0; port && i < TB_PATH_MAX_HOPS; i++) {
+		sw = port->sw;
+
+		ret = tb_port_read(port, &hop, TB_CFG_HOPS, 2 * hopid, 2);
+		if (ret) {
+			tb_port_warn(port, "failed to read path at %d\n", hopid);
+			return NULL;
+		}
+
+		if (!hop.enable)
+			return NULL;
+
+		out_port = &sw->ports[hop.out_port];
+		hopid = hop.next_hop;
+		port = out_port->remote;
+	}
+
+	return out_port && hopid == dst_hopid ? out_port : NULL;
+}
+
+static int tb_path_find_src_hopid(struct tb_port *src,
+	const struct tb_port *dst, int dst_hopid)
+{
+	struct tb_port *out;
+	int i;
+
+	for (i = TB_PATH_MIN_HOPID; i <= src->config.max_in_hop_id; i++) {
+		out = tb_path_find_dst_port(src, i, dst_hopid);
+		if (out == dst)
+			return i;
+	}
+
+	return 0;
+}
+
+/**
+ * tb_path_discover() - Discover a path
+ * @src: First input port of a path
+ * @src_hopid: Starting HopID of a path (%-1 if don't care)
+ * @dst: Expected destination port of the path (%NULL if don't care)
+ * @dst_hopid: HopID to the @dst (%-1 if don't care)
+ * @last: Last port is filled here if not %NULL
+ * @name: Name of the path
+ *
+ * Follows a path starting from @src and @src_hopid to the last output
+ * port of the path. Allocates HopIDs for the visited ports. Call
+ * tb_path_free() to release the path and allocated HopIDs when the path
+ * is not needed anymore.
+ *
+ * Note function discovers also incomplete paths so caller should check
+ * that the @dst port is the expected one. If it is not, the path can be
+ * cleaned up by calling tb_path_deactivate() before tb_path_free().
+ *
+ * Return: Discovered path on success, %NULL in case of failure
+ */
+struct tb_path *tb_path_discover(struct tb_port *src, int src_hopid,
+				 struct tb_port *dst, int dst_hopid,
+				 struct tb_port **last, const char *name)
+{
+	struct tb_port *out_port;
+	struct tb_regs_hop hop;
+	struct tb_path *path;
+	struct tb_switch *sw;
+	struct tb_port *p;
+	size_t num_hops;
+	int ret, i, h;
+
+	if (src_hopid < 0 && dst) {
+		/*
+		 * For incomplete paths the intermediate HopID can be
+		 * different from the one used by the protocol adapter
+		 * so in that case find a path that ends on @dst with
+		 * matching @dst_hopid. That should give us the correct
+		 * HopID for the @src.
+		 */
+		src_hopid = tb_path_find_src_hopid(src, dst, dst_hopid);
+		if (!src_hopid)
+			return NULL;
+	}
+
+	p = src;
+	h = src_hopid;
+	num_hops = 0;
+
+	for (i = 0; p && i < TB_PATH_MAX_HOPS; i++) {
+		sw = p->sw;
+
+		ret = tb_port_read(p, &hop, TB_CFG_HOPS, 2 * h, 2);
+		if (ret) {
+			tb_port_warn(p, "failed to read path at %d\n", h);
+			return NULL;
+		}
+
+		/* If the hop is not enabled we got an incomplete path */
+		if (!hop.enable)
+			break;
+
+		out_port = &sw->ports[hop.out_port];
+		if (last)
+			*last = out_port;
+
+		h = hop.next_hop;
+		p = out_port->remote;
+		num_hops++;
+	}
+
+	path = kzalloc(sizeof(*path), GFP_KERNEL);
+	if (!path)
+		return NULL;
+
+	path->name = name;
+	path->tb = src->sw->tb;
+	path->path_length = num_hops;
+	path->activated = true;
+
+	path->hops = kcalloc(num_hops, sizeof(*path->hops), GFP_KERNEL);
+	if (!path->hops) {
+		kfree(path);
+		return NULL;
+	}
+
+	p = src;
+	h = src_hopid;
+
+	for (i = 0; i < num_hops; i++) {
+		int next_hop;
+
+		sw = p->sw;
+
+		ret = tb_port_read(p, &hop, TB_CFG_HOPS, 2 * h, 2);
+		if (ret) {
+			tb_port_warn(p, "failed to read path at %d\n", h);
+			goto err;
+		}
+
+		if (tb_port_alloc_in_hopid(p, h, h) < 0)
+			goto err;
+
+		out_port = &sw->ports[hop.out_port];
+		next_hop = hop.next_hop;
+
+		if (tb_port_alloc_out_hopid(out_port, next_hop, next_hop) < 0) {
+			tb_port_release_in_hopid(p, h);
+			goto err;
+		}
+
+		path->hops[i].in_port = p;
+		path->hops[i].in_hop_index = h;
+		path->hops[i].in_counter_index = -1;
+		path->hops[i].out_port = out_port;
+		path->hops[i].next_hop_index = next_hop;
+
+		h = next_hop;
+		p = out_port->remote;
+	}
+
+	return path;
+
+err:
+	tb_port_warn(src, "failed to discover path starting at HopID %d\n",
+		     src_hopid);
+	tb_path_free(path);
+	return NULL;
+}
+
 /**
  * tb_path_alloc() - allocate a thunderbolt path between two ports
  * @tb: Domain pointer
@@ -283,30 +459,14 @@ int tb_path_activate(struct tb_path *path)
 	for (i = path->path_length - 1; i >= 0; i--) {
 		struct tb_regs_hop hop = { 0 };
 
-		/*
-		 * We do (currently) not tear down paths setup by the firmeware.
-		 * If a firmware device is unplugged and plugged in again then
-		 * it can happen that we reuse some of the hops from the (now
-		 * defunct) firmeware path. This causes the hotplug operation to
-		 * fail (the pci device does not show up). Clearing the hop
-		 * before overwriting it fixes the problem.
-		 *
-		 * Should be removed once we discover and tear down firmeware
-		 * paths.
-		 */
-		res = tb_port_write(path->hops[i].in_port, &hop, TB_CFG_HOPS,
-				    2 * path->hops[i].in_hop_index, 2);
-		if (res) {
-			__tb_path_deactivate_hops(path, i);
-			__tb_path_deallocate_nfc(path, 0);
-			goto err;
-		}
+		/* If it is left active deactivate it first */
+		__tb_path_deactivate_hop(path->hops[i].in_port,
+				path->hops[i].in_hop_index);
 
 		/* dword 0 */
 		hop.next_hop = path->hops[i].next_hop_index;
 		hop.out_port = path->hops[i].out_port->port;
-		/* TODO: figure out why these are good values */
-		hop.initial_credits = (i == path->path_length - 1) ? 16 : 7;
+		hop.initial_credits = path->hops[i].initial_credits;
 		hop.unknown1 = 0;
 		hop.enable = 1;