linux/drivers/firewire/core-topology.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Incremental bus scan, based on bus topology
 *
 * Copyright (C) 2004-2006 Kristian Hoegsberg <krh@bitplanet.net>
 */

#include <linux/bug.h>
#include <linux/errno.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <linux/atomic.h>
#include <asm/byteorder.h>

#include "core.h"
#include "phy-packet-definitions.h"
#include <trace/events/firewire.h>

static struct fw_node *fw_node_create(u32 sid, int port_count, int color)
{
	struct fw_node *node;

	node = kzalloc(struct_size(node, ports, port_count), GFP_ATOMIC);
	if (node == NULL)
		return NULL;

	node->color = color;
	node->node_id = LOCAL_BUS | phy_packet_self_id_get_phy_id(sid);
	node->link_on = phy_packet_self_id_zero_get_link_active(sid);
	// NOTE: Only two bits, thus only for SCODE_100, SCODE_200, SCODE_400, and SCODE_BETA.
	node->phy_speed = phy_packet_self_id_zero_get_scode(sid);
	node->initiated_reset = phy_packet_self_id_zero_get_initiated_reset(sid);
	node->port_count = port_count;

	kref_init(&node->kref);
	INIT_LIST_HEAD(&node->link);

	return node;
}

/*
 * Compute the maximum hop count for this node and it's children.  The
 * maximum hop count is the maximum number of connections between any
 * two nodes in the subtree rooted at this node.  We need this for
 * setting the gap count.  As we build the tree bottom up in
 * build_tree() below, this is fairly easy to do: for each node we
 * maintain the max hop count and the max depth, ie the number of hops
 * to the furthest leaf.  Computing the max hop count breaks down into
 * two cases: either the path goes through this node, in which case
 * the hop count is the sum of the two biggest child depths plus 2.
 * Or it could be the case that the max hop path is entirely
 * contained in a child tree, in which case the max hop count is just
 * the max hop count of this child.
 */
static void update_hop_count(struct fw_node *node)
{
	int depths[2] = { -1, -1 };
	int max_child_hops = 0;
	int i;

	for (i = 0; i < node->port_count; i++) {
		if (node->ports[i] == NULL)
			continue;

		if (node->ports[i]->max_hops > max_child_hops)
			max_child_hops = node->ports[i]->max_hops;

		if (node->ports[i]->max_depth > depths[0]) {
			depths[1] = depths[0];
			depths[0] = node->ports[i]->max_depth;
		} else if (node->ports[i]->max_depth > depths[1])
			depths[1] = node->ports[i]->max_depth;
	}

	node->max_depth = depths[0] + 1;
	node->max_hops = max(max_child_hops, depths[0] + depths[1] + 2);
}

static inline struct fw_node *fw_node(struct list_head *l)
{
	return list_entry(l, struct fw_node, link);
}

/*
 * This function builds the tree representation of the topology given
 * by the self IDs from the latest bus reset.  During the construction
 * of the tree, the function checks that the self IDs are valid and
 * internally consistent.  On success this function returns the
 * fw_node corresponding to the local card otherwise NULL.
 */
static struct fw_node *build_tree(struct fw_card *card, const u32 *sid, int self_id_count,
				  unsigned int generation)
{
	struct self_id_sequence_enumerator enumerator = {
		.cursor = sid,
		.quadlet_count = self_id_count,
	};
	struct fw_node *node, *child, *local_node, *irm_node;
	struct list_head stack;
	int phy_id, stack_depth;
	int gap_count;
	bool beta_repeaters_present;

	local_node = NULL;
	node = NULL;
	INIT_LIST_HEAD(&stack);
	stack_depth = 0;
	phy_id = 0;
	irm_node = NULL;
	gap_count = phy_packet_self_id_zero_get_gap_count(*sid);
	beta_repeaters_present = false;

	while (enumerator.quadlet_count > 0) {
		unsigned int child_port_count = 0;
		unsigned int total_port_count = 0;
		unsigned int parent_count = 0;
		unsigned int quadlet_count;
		const u32 *self_id_sequence;
		unsigned int port_capacity;
		enum phy_packet_self_id_port_status port_status;
		unsigned int port_index;
		struct list_head *h;
		int i;

		self_id_sequence = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
		if (IS_ERR(self_id_sequence)) {
			if (PTR_ERR(self_id_sequence) != -ENODATA) {
				fw_err(card, "inconsistent extended self IDs: %ld\n",
				       PTR_ERR(self_id_sequence));
				return NULL;
			}
			break;
		}

		port_capacity = self_id_sequence_get_port_capacity(quadlet_count);
		trace_self_id_sequence(card->index, self_id_sequence, quadlet_count, generation);

		for (port_index = 0; port_index < port_capacity; ++port_index) {
			port_status = self_id_sequence_get_port_status(self_id_sequence, quadlet_count,
								       port_index);
			switch (port_status) {
			case PHY_PACKET_SELF_ID_PORT_STATUS_CHILD:
				++child_port_count;
				fallthrough;
			case PHY_PACKET_SELF_ID_PORT_STATUS_PARENT:
			case PHY_PACKET_SELF_ID_PORT_STATUS_NCONN:
				++total_port_count;
				fallthrough;
			case PHY_PACKET_SELF_ID_PORT_STATUS_NONE:
			default:
				break;
			}
		}

		if (phy_id != phy_packet_self_id_get_phy_id(self_id_sequence[0])) {
			fw_err(card, "PHY ID mismatch in self ID: %d != %d\n",
			       phy_id, phy_packet_self_id_get_phy_id(self_id_sequence[0]));
			return NULL;
		}

		if (child_port_count > stack_depth) {
			fw_err(card, "topology stack underflow\n");
			return NULL;
		}

		/*
		 * Seek back from the top of our stack to find the
		 * start of the child nodes for this node.
		 */
		for (i = 0, h = &stack; i < child_port_count; i++)
			h = h->prev;
		/*
		 * When the stack is empty, this yields an invalid value,
		 * but that pointer will never be dereferenced.
		 */
		child = fw_node(h);

		node = fw_node_create(self_id_sequence[0], total_port_count, card->color);
		if (node == NULL) {
			fw_err(card, "out of memory while building topology\n");
			return NULL;
		}

		if (phy_id == (card->node_id & 0x3f))
			local_node = node;

		if (phy_packet_self_id_zero_get_contender(self_id_sequence[0]))
			irm_node = node;

		for (port_index = 0; port_index < total_port_count; ++port_index) {
			port_status = self_id_sequence_get_port_status(self_id_sequence, quadlet_count,
								       port_index);
			switch (port_status) {
			case PHY_PACKET_SELF_ID_PORT_STATUS_PARENT:
				// Who's your daddy?  We dont know the parent node at this time, so
				// we temporarily abuse node->color for remembering the entry in
				// the node->ports array where the parent node should be.  Later,
				// when we handle the parent node, we fix up the reference.
				++parent_count;
				node->color = port_index;
				break;

			case PHY_PACKET_SELF_ID_PORT_STATUS_CHILD:
				node->ports[port_index] = child;
				// Fix up parent reference for this child node.
				child->ports[child->color] = node;
				child->color = card->color;
				child = fw_node(child->link.next);
				break;
			case PHY_PACKET_SELF_ID_PORT_STATUS_NCONN:
			case PHY_PACKET_SELF_ID_PORT_STATUS_NONE:
			default:
				break;
			}
		}

		// Check that the node reports exactly one parent port, except for the root, which
		// of course should have no parents.
		if ((enumerator.quadlet_count == 0 && parent_count != 0) ||
		    (enumerator.quadlet_count > 0 && parent_count != 1)) {
			fw_err(card, "parent port inconsistency for node %d: "
			       "parent_count=%d\n", phy_id, parent_count);
			return NULL;
		}

		/* Pop the child nodes off the stack and push the new node. */
		__list_del(h->prev, &stack);
		list_add_tail(&node->link, &stack);
		stack_depth += 1 - child_port_count;

		if (node->phy_speed == SCODE_BETA && parent_count + child_port_count > 1)
			beta_repeaters_present = true;

		// If PHYs report different gap counts, set an invalid count which will force a gap
		// count reconfiguration and a reset.
		if (phy_packet_self_id_zero_get_gap_count(self_id_sequence[0]) != gap_count)
			gap_count = GAP_COUNT_MISMATCHED;

		update_hop_count(node);

		phy_id++;
	}

	card->root_node = node;
	card->irm_node = irm_node;
	card->gap_count = gap_count;
	card->beta_repeaters_present = beta_repeaters_present;

	return local_node;
}

typedef void (*fw_node_callback_t)(struct fw_card * card,
				   struct fw_node * node,
				   struct fw_node * parent);

static void for_each_fw_node(struct fw_card *card, struct fw_node *root,
			     fw_node_callback_t callback)
{
	struct list_head list;
	struct fw_node *node, *next, *child, *parent;
	int i;

	INIT_LIST_HEAD(&list);

	fw_node_get(root);
	list_add_tail(&root->link, &list);
	parent = NULL;
	list_for_each_entry(node, &list, link) {
		node->color = card->color;

		for (i = 0; i < node->port_count; i++) {
			child = node->ports[i];
			if (!child)
				continue;
			if (child->color == card->color)
				parent = child;
			else {
				fw_node_get(child);
				list_add_tail(&child->link, &list);
			}
		}

		callback(card, node, parent);
	}

	list_for_each_entry_safe(node, next, &list, link)
		fw_node_put(node);
}

static void report_lost_node(struct fw_card *card,
			     struct fw_node *node, struct fw_node *parent)
{
	fw_node_event(card, node, FW_NODE_DESTROYED);
	fw_node_put(node);

	/* Topology has changed - reset bus manager retry counter */
	card->bm_retries = 0;
}

static void report_found_node(struct fw_card *card,
			      struct fw_node *node, struct fw_node *parent)
{
	int b_path = (node->phy_speed == SCODE_BETA);

	if (parent != NULL) {
		/* min() macro doesn't work here with gcc 3.4 */
		node->max_speed = parent->max_speed < node->phy_speed ?
					parent->max_speed : node->phy_speed;
		node->b_path = parent->b_path && b_path;
	} else {
		node->max_speed = node->phy_speed;
		node->b_path = b_path;
	}

	fw_node_event(card, node, FW_NODE_CREATED);

	/* Topology has changed - reset bus manager retry counter */
	card->bm_retries = 0;
}

void fw_destroy_nodes(struct fw_card *card)
__must_hold(&card->lock)
{
	lockdep_assert_held(&card->lock);

	card->color++;
	if (card->local_node != NULL)
		for_each_fw_node(card, card->local_node, report_lost_node);
	card->local_node = NULL;
}

static void move_tree(struct fw_node *node0, struct fw_node *node1, int port)
{
	struct fw_node *tree;
	int i;

	tree = node1->ports[port];
	node0->ports[port] = tree;
	for (i = 0; i < tree->port_count; i++) {
		if (tree->ports[i] == node1) {
			tree->ports[i] = node0;
			break;
		}
	}
}

/*
 * Compare the old topology tree for card with the new one specified by root.
 * Queue the nodes and mark them as either found, lost or updated.
 * Update the nodes in the card topology tree as we go.
 */
static void update_tree(struct fw_card *card, struct fw_node *root)
{
	struct list_head list0, list1;
	struct fw_node *node0, *node1, *next1;
	int i, event;

	INIT_LIST_HEAD(&list0);
	list_add_tail(&card->local_node->link, &list0);
	INIT_LIST_HEAD(&list1);
	list_add_tail(&root->link, &list1);

	node0 = fw_node(list0.next);
	node1 = fw_node(list1.next);

	while (&node0->link != &list0) {
		WARN_ON(node0->port_count != node1->port_count);

		if (node0->link_on && !node1->link_on)
			event = FW_NODE_LINK_OFF;
		else if (!node0->link_on && node1->link_on)
			event = FW_NODE_LINK_ON;
		else if (node1->initiated_reset && node1->link_on)
			event = FW_NODE_INITIATED_RESET;
		else
			event = FW_NODE_UPDATED;

		node0->node_id = node1->node_id;
		node0->color = card->color;
		node0->link_on = node1->link_on;
		node0->initiated_reset = node1->initiated_reset;
		node0->max_hops = node1->max_hops;
		node1->color = card->color;
		fw_node_event(card, node0, event);

		if (card->root_node == node1)
			card->root_node = node0;
		if (card->irm_node == node1)
			card->irm_node = node0;

		for (i = 0; i < node0->port_count; i++) {
			if (node0->ports[i] && node1->ports[i]) {
				/*
				 * This port didn't change, queue the
				 * connected node for further
				 * investigation.
				 */
				if (node0->ports[i]->color == card->color)
					continue;
				list_add_tail(&node0->ports[i]->link, &list0);
				list_add_tail(&node1->ports[i]->link, &list1);
			} else if (node0->ports[i]) {
				/*
				 * The nodes connected here were
				 * unplugged; unref the lost nodes and
				 * queue FW_NODE_LOST callbacks for
				 * them.
				 */

				for_each_fw_node(card, node0->ports[i],
						 report_lost_node);
				node0->ports[i] = NULL;
			} else if (node1->ports[i]) {
				/*
				 * One or more node were connected to
				 * this port. Move the new nodes into
				 * the tree and queue FW_NODE_CREATED
				 * callbacks for them.
				 */
				move_tree(node0, node1, i);
				for_each_fw_node(card, node0->ports[i],
						 report_found_node);
			}
		}

		node0 = fw_node(node0->link.next);
		next1 = fw_node(node1->link.next);
		fw_node_put(node1);
		node1 = next1;
	}
}

static void update_topology_map(__be32 *buffer, size_t buffer_size, int root_node_id,
				const u32 *self_ids, int self_id_count)
{
	__be32 *map = buffer;
	int node_count = (root_node_id & 0x3f) + 1;

	memset(map, 0, buffer_size);

	*map++ = cpu_to_be32((self_id_count + 2) << 16);
	*map++ = cpu_to_be32(be32_to_cpu(buffer[1]) + 1);
	*map++ = cpu_to_be32((node_count << 16) | self_id_count);

	while (self_id_count--)
		*map++ = cpu_to_be32p(self_ids++);

	fw_compute_block_crc(buffer);
}

void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
			      int self_id_count, u32 *self_ids, bool bm_abdicate)
{
	struct fw_node *local_node;

	trace_bus_reset_handle(card->index, generation, node_id, bm_abdicate, self_ids, self_id_count);

	scoped_guard(spinlock, &card->lock) {
		// If the selfID buffer is not the immediate successor of the
		// previously processed one, we cannot reliably compare the
		// old and new topologies.
		if (!is_next_generation(generation, card->generation) && card->local_node != NULL) {
			fw_destroy_nodes(card);
			card->bm_retries = 0;
		}
		card->broadcast_channel_allocated = card->broadcast_channel_auto_allocated;
		card->node_id = node_id;
		// Update node_id before generation to prevent anybody from using
		// a stale node_id together with a current generation.
		smp_wmb();
		card->generation = generation;
		card->reset_jiffies = get_jiffies_64();
		card->bm_node_id  = 0xffff;
		card->bm_abdicate = bm_abdicate;

		local_node = build_tree(card, self_ids, self_id_count, generation);

		card->color++;

		if (local_node == NULL) {
			fw_err(card, "topology build failed\n");
			// FIXME: We need to issue a bus reset in this case.
		} else if (card->local_node == NULL) {
			card->local_node = local_node;
			for_each_fw_node(card, local_node, report_found_node);
		} else {
			update_tree(card, local_node);
		}
	}

	fw_schedule_bm_work(card, 0);

	// Just used by transaction layer.
	scoped_guard(spinlock, &card->topology_map.lock) {
		update_topology_map(card->topology_map.buffer, sizeof(card->topology_map.buffer),
				    card->root_node->node_id, self_ids, self_id_count);
	}
}
EXPORT_SYMBOL(fw_core_handle_bus_reset);