thunderbolt: Add path setup code.

A thunderbolt path is a unidirectional channel between two thunderbolt
ports. Two such paths are needed to establish a pci tunnel.

This patch introduces struct tb_path as well as a set of tb_path_*
methods which are used to activate & deactivate paths.
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/thunderbolt/Makefile

 obj-${CONFIG_THUNDERBOLT} := thunderbolt.o
-thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o
+thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o path.o
 

drivers/thunderbolt/path.c

+/*
+ * Thunderbolt Cactus Ridge driver - path/tunnel functionality
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+
+#include "tb.h"
+
+
+static void tb_dump_hop(struct tb_port *port, struct tb_regs_hop *hop)
+{
+	tb_port_info(port, " Hop through port %d to hop %d (%s)\n",
+		     hop->out_port, hop->next_hop,
+		     hop->enable ? "enabled" : "disabled");
+	tb_port_info(port, "  Weight: %d Priority: %d Credits: %d Drop: %d\n",
+		     hop->weight, hop->priority,
+		     hop->initial_credits, hop->drop_packages);
+	tb_port_info(port, "   Counter enabled: %d Counter index: %d\n",
+		     hop->counter_enable, hop->counter);
+	tb_port_info(port, "  Flow Control (In/Eg): %d/%d Shared Buffer (In/Eg): %d/%d\n",
+		     hop->ingress_fc, hop->egress_fc,
+		     hop->ingress_shared_buffer, hop->egress_shared_buffer);
+	tb_port_info(port, "  Unknown1: %#x Unknown2: %#x Unknown3: %#x\n",
+		     hop->unknown1, hop->unknown2, hop->unknown3);
+}
+
+/**
+ * tb_path_alloc() - allocate a thunderbolt path
+ *
+ * Return: Returns a tb_path on success or NULL on failure.
+ */
+struct tb_path *tb_path_alloc(struct tb *tb, int num_hops)
+{
+	struct tb_path *path = kzalloc(sizeof(*path), GFP_KERNEL);
+	if (!path)
+		return NULL;
+	path->hops = kcalloc(num_hops, sizeof(*path->hops), GFP_KERNEL);
+	if (!path->hops) {
+		kfree(path);
+		return NULL;
+	}
+	path->tb = tb;
+	path->path_length = num_hops;
+	return path;
+}
+
+/**
+ * tb_path_free() - free a deactivated path
+ */
+void tb_path_free(struct tb_path *path)
+{
+	if (path->activated) {
+		tb_WARN(path->tb, "trying to free an activated path\n")
+		return;
+	}
+	kfree(path->hops);
+	kfree(path);
+}
+
+static void __tb_path_deallocate_nfc(struct tb_path *path, int first_hop)
+{
+	int i, res;
+	for (i = first_hop; i < path->path_length; i++) {
+		res = tb_port_add_nfc_credits(path->hops[i].in_port,
+					      -path->nfc_credits);
+		if (res)
+			tb_port_warn(path->hops[i].in_port,
+				     "nfc credits deallocation failed for hop %d\n",
+				     i);
+	}
+}
+
+static void __tb_path_deactivate_hops(struct tb_path *path, int first_hop)
+{
+	int i, res;
+	struct tb_regs_hop hop = { };
+	for (i = first_hop; i < path->path_length; i++) {
+		res = tb_port_write(path->hops[i].in_port, &hop, TB_CFG_HOPS,
+				    2 * path->hops[i].in_hop_index, 2);
+		if (res)
+			tb_port_warn(path->hops[i].in_port,
+				     "hop deactivation failed for hop %d, index %d\n",
+				     i, path->hops[i].in_hop_index);
+	}
+}
+
+void tb_path_deactivate(struct tb_path *path)
+{
+	if (!path->activated) {
+		tb_WARN(path->tb, "trying to deactivate an inactive path\n");
+		return;
+	}
+	tb_info(path->tb,
+		"deactivating path from %llx:%x to %llx:%x\n",
+		tb_route(path->hops[0].in_port->sw),
+		path->hops[0].in_port->port,
+		tb_route(path->hops[path->path_length - 1].out_port->sw),
+		path->hops[path->path_length - 1].out_port->port);
+	__tb_path_deactivate_hops(path, 0);
+	__tb_path_deallocate_nfc(path, 0);
+	path->activated = false;
+}
+
+/**
+ * tb_path_activate() - activate a path
+ *
+ * Activate a path starting with the last hop and iterating backwards. The
+ * caller must fill path->hops before calling tb_path_activate().
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int tb_path_activate(struct tb_path *path)
+{
+	int i, res;
+	enum tb_path_port out_mask, in_mask;
+	if (path->activated) {
+		tb_WARN(path->tb, "trying to activate already activated path\n");
+		return -EINVAL;
+	}
+
+	tb_info(path->tb,
+		"activating path from %llx:%x to %llx:%x\n",
+		tb_route(path->hops[0].in_port->sw),
+		path->hops[0].in_port->port,
+		tb_route(path->hops[path->path_length - 1].out_port->sw),
+		path->hops[path->path_length - 1].out_port->port);
+
+	/* Clear counters. */
+	for (i = path->path_length - 1; i >= 0; i--) {
+		if (path->hops[i].in_counter_index == -1)
+			continue;
+		res = tb_port_clear_counter(path->hops[i].in_port,
+					    path->hops[i].in_counter_index);
+		if (res)
+			goto err;
+	}
+
+	/* Add non flow controlled credits. */
+	for (i = path->path_length - 1; i >= 0; i--) {
+		res = tb_port_add_nfc_credits(path->hops[i].in_port,
+					      path->nfc_credits);
+		if (res) {
+			__tb_path_deallocate_nfc(path, i);
+			goto err;
+		}
+	}
+
+	/* Activate hops. */
+	for (i = path->path_length - 1; i >= 0; i--) {
+		struct tb_regs_hop hop;
+
+		/* 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.unknown1 = 0;
+		hop.enable = 1;
+
+		/* dword 1 */
+		out_mask = (i == path->path_length - 1) ?
+				TB_PATH_DESTINATION : TB_PATH_INTERNAL;
+		in_mask = (i == 0) ? TB_PATH_SOURCE : TB_PATH_INTERNAL;
+		hop.weight = path->weight;
+		hop.unknown2 = 0;
+		hop.priority = path->priority;
+		hop.drop_packages = path->drop_packages;
+		hop.counter = path->hops[i].in_counter_index;
+		hop.counter_enable = path->hops[i].in_counter_index != -1;
+		hop.ingress_fc = path->ingress_fc_enable & in_mask;
+		hop.egress_fc = path->egress_fc_enable & out_mask;
+		hop.ingress_shared_buffer = path->ingress_shared_buffer
+					    & in_mask;
+		hop.egress_shared_buffer = path->egress_shared_buffer
+					    & out_mask;
+		hop.unknown3 = 0;
+
+		tb_port_info(path->hops[i].in_port, "Writing hop %d, index %d",
+			     i, path->hops[i].in_hop_index);
+		tb_dump_hop(path->hops[i].in_port, &hop);
+		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;
+		}
+	}
+	path->activated = true;
+	tb_info(path->tb, "path activation complete\n");
+	return 0;
+err:
+	tb_WARN(path->tb, "path activation failed\n");
+	return res;
+}
+
+/**
+ * tb_path_is_invalid() - check whether any ports on the path are invalid
+ *
+ * Return: Returns true if the path is invalid, false otherwise.
+ */
+bool tb_path_is_invalid(struct tb_path *path)
+{
+	int i = 0;
+	for (i = 0; i < path->path_length; i++) {
+		if (path->hops[i].in_port->sw->is_unplugged)
+			return true;
+		if (path->hops[i].out_port->sw->is_unplugged)
+			return true;
+	}
+	return false;
+}

drivers/thunderbolt/switch.c

@@ -138,6 +138,40 @@ int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged)
 	return 0;
 }
 
+/**
+ * tb_port_add_nfc_credits() - add/remove non flow controlled credits to port
+ *
+ * Change the number of NFC credits allocated to @port by @credits. To remove
+ * NFC credits pass a negative amount of credits.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int tb_port_add_nfc_credits(struct tb_port *port, int credits)
+{
+	if (credits == 0)
+		return 0;
+	tb_port_info(port,
+		     "adding %#x NFC credits (%#x -> %#x)",
+		     credits,
+		     port->config.nfc_credits,
+		     port->config.nfc_credits + credits);
+	port->config.nfc_credits += credits;
+	return tb_port_write(port, &port->config.nfc_credits,
+			     TB_CFG_PORT, 4, 1);
+}
+
+/**
+ * tb_port_clear_counter() - clear a counter in TB_CFG_COUNTER
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int tb_port_clear_counter(struct tb_port *port, int counter)
+{
+	u32 zero[3] = { 0, 0, 0 };
+	tb_port_info(port, "clearing counter %d\n", counter);
+	return tb_port_write(port, zero, TB_CFG_COUNTERS, 3 * counter, 3);
+}
+
 /**
  * tb_init_port() - initialize a port
  *

drivers/thunderbolt/tb.h

@@ -34,6 +34,60 @@ struct tb_port {
 	u8 port; /* port number on switch */
 };
 
+/**
+ * struct tb_path_hop - routing information for a tb_path
+ *
+ * Hop configuration is always done on the IN port of a switch.
+ * in_port and out_port have to be on the same switch. Packets arriving on
+ * in_port with "hop" = in_hop_index will get routed to through out_port. The
+ * next hop to take (on out_port->remote) is determined by next_hop_index.
+ *
+ * in_counter_index is the index of a counter (in TB_CFG_COUNTERS) on the in
+ * port.
+ */
+struct tb_path_hop {
+	struct tb_port *in_port;
+	struct tb_port *out_port;
+	int in_hop_index;
+	int in_counter_index; /* write -1 to disable counters for this hop. */
+	int next_hop_index;
+};
+
+/**
+ * enum tb_path_port - path options mask
+ */
+enum tb_path_port {
+	TB_PATH_NONE = 0,
+	TB_PATH_SOURCE = 1, /* activate on the first hop (out of src) */
+	TB_PATH_INTERNAL = 2, /* activate on other hops (not the first/last) */
+	TB_PATH_DESTINATION = 4, /* activate on the last hop (into dst) */
+	TB_PATH_ALL = 7,
+};
+
+/**
+ * struct tb_path - a unidirectional path between two ports
+ *
+ * A path consists of a number of hops (see tb_path_hop). To establish a PCIe
+ * tunnel two paths have to be created between the two PCIe ports.
+ *
+ */
+struct tb_path {
+	struct tb *tb;
+	int nfc_credits; /* non flow controlled credits */
+	enum tb_path_port ingress_shared_buffer;
+	enum tb_path_port egress_shared_buffer;
+	enum tb_path_port ingress_fc_enable;
+	enum tb_path_port egress_fc_enable;
+
+	int priority:3;
+	int weight:4;
+	bool drop_packages;
+	bool activated;
+	struct tb_path_hop *hops;
+	int path_length; /* number of hops */
+};
+
+
 /**
  * struct tb - main thunderbolt bus structure
  */
@@ -165,9 +219,17 @@ void tb_sw_set_unpplugged(struct tb_switch *sw);
 struct tb_switch *get_switch_at_route(struct tb_switch *sw, u64 route);
 
 int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged);
+int tb_port_add_nfc_credits(struct tb_port *port, int credits);
+int tb_port_clear_counter(struct tb_port *port, int counter);
 
 int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, u32 value);
 
+struct tb_path *tb_path_alloc(struct tb *tb, int num_hops);
+void tb_path_free(struct tb_path *path);
+int tb_path_activate(struct tb_path *path);
+void tb_path_deactivate(struct tb_path *path);
+bool tb_path_is_invalid(struct tb_path *path);
+
 
 static inline int tb_route_length(u64 route)
 {