device/device.h: Drop multiple links

Multiple links are unused throughout the tree and make the code more
confusing as an iteration over all busses is needed to get downstream
devices. This also not done consistently e.g. the allocator does not
care about multiple links on busses. A better way of dealing multiple
links below a device is to feature dummy devices with each their
respective bus.

This drops the sconfig capability to declare the same device multiple
times which was previously used to declare multiple links.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: Iab6fe269faef46ae77ed1ea425440cf5c7dbd49b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78328
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jincheng Li <jincheng.li@intel.com>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>

16 files changed, 186 insertions, 354 deletions

diff --git a/src/arch/x86/mpspec.c b/src/arch/x86/mpspec.c
index 7744f68e8502..3ddee2f6b9ac 100644
--- a/src/arch/x86/mpspec.c
+++ b/src/arch/x86/mpspec.c
@@ -282,48 +282,46 @@ void smp_write_intsrc_pci_bridge(struct mp_config_table *mc,
 	int srcbus;
 	int slot;
 
-	struct bus *link;
 	unsigned char dstirq_x[4];
 
-	for (link = dev->link_list; link; link = link->next) {
+	if (!dev->link_list)
+		return;
 
-		child = link->children;
-		srcbus = link->secondary;
+	child = dev->link_list->children;
+	srcbus = dev->link_list->secondary;
 
-		while (child) {
-			if (child->path.type != DEVICE_PATH_PCI)
-				goto next;
+	while (child) {
+		if (child->path.type != DEVICE_PATH_PCI)
+			goto next;
 
-			slot = (child->path.pci.devfn >> 3);
-			/* round pins */
-			for (i = 0; i < 4; i++)
-				dstirq_x[i] = dstirq[(i + slot) % 4];
-
-			if ((child->class >> 16) != PCI_BASE_CLASS_BRIDGE) {
-				/* pci device */
-				printk(BIOS_DEBUG, "route irq: %s\n",
-					dev_path(child));
-				for (i = 0; i < 4; i++)
-					smp_write_intsrc(mc, irqtype, irqflag,
-						srcbus, (slot<<2)|i, dstapic,
-						dstirq_x[i]);
-				goto next;
-			}
+		slot = (child->path.pci.devfn >> 3);
+		/* round pins */
+		for (i = 0; i < 4; i++)
+			dstirq_x[i] = dstirq[(i + slot) % 4];
 
-			switch (child->class>>8) {
-			case PCI_CLASS_BRIDGE_PCI:
-			case PCI_CLASS_BRIDGE_PCMCIA:
-			case PCI_CLASS_BRIDGE_CARDBUS:
-				printk(BIOS_DEBUG, "route irq bridge: %s\n",
-					dev_path(child));
-				smp_write_intsrc_pci_bridge(mc, irqtype,
-					irqflag, child, dstapic, dstirq_x);
-			}
+		if ((child->class >> 16) != PCI_BASE_CLASS_BRIDGE) {
+			/* pci device */
+			printk(BIOS_DEBUG, "route irq: %s\n",
+			       dev_path(child));
+			for (i = 0; i < 4; i++)
+				smp_write_intsrc(mc, irqtype, irqflag,
+						 srcbus, (slot<<2)|i, dstapic,
+						 dstirq_x[i]);
+			goto next;
+		}
 
-next:
-			child = child->sibling;
+		switch (child->class>>8) {
+		case PCI_CLASS_BRIDGE_PCI:
+		case PCI_CLASS_BRIDGE_PCMCIA:
+		case PCI_CLASS_BRIDGE_CARDBUS:
+			printk(BIOS_DEBUG, "route irq bridge: %s\n",
+			       dev_path(child));
+			smp_write_intsrc_pci_bridge(mc, irqtype,
+						    irqflag, child, dstapic, dstirq_x);
 		}
 
+next:
+		child = child->sibling;
 	}
 }
 
@@ -478,17 +476,16 @@ void mptable_write_buses(struct mp_config_table *mc, int *max_pci_bus,
 	memset(buses, 0, sizeof(buses));
 
 	for (dev = all_devices; dev; dev = dev->next) {
-		struct bus *bus;
-		for (bus = dev->link_list; bus; bus = bus->next) {
-			if (bus->secondary > 255) {
-				printk(BIOS_ERR,
-					"A bus claims to have a bus ID > 255?!? Aborting");
-				return;
-			}
-			buses[bus->secondary] = 1;
-			if (highest < bus->secondary)
-				highest = bus->secondary;
+		struct bus *bus = dev->link_list;
+		if (!bus)
+			continue;
+		if (bus->secondary > 255) {
+			printk(BIOS_ERR, "A bus claims to have a bus ID > 255?!? Aborting\n");
+			return;
 		}
+		buses[bus->secondary] = 1;
+		if (highest < bus->secondary)
+			highest = bus->secondary;
 	}
 	for (i = 0; i <= highest; i++) {
 		if (buses[i]) {
diff --git a/src/device/device.c b/src/device/device.c
index d877e14eabe6..743a3af6c200 100644
--- a/src/device/device.c
+++ b/src/device/device.c
@@ -187,13 +187,11 @@ static void read_resources(struct bus *bus)
 {
 	struct device *curdev;
 
-	printk(BIOS_SPEW, "%s %s segment group %d bus %d link: %d\n", dev_path(bus->dev),
-	       __func__, bus->segment_group, bus->secondary, bus->link_num);
+	printk(BIOS_SPEW, "%s %s segment group %d bus %d\n", dev_path(bus->dev),
+	       __func__, bus->segment_group, bus->secondary);
 
 	/* Walk through all devices and find which resources they need. */
 	for (curdev = bus->children; curdev; curdev = curdev->sibling) {
-		struct bus *link;
-
 		if (!curdev->enabled)
 			continue;
 
@@ -207,12 +205,12 @@ static void read_resources(struct bus *bus)
 		curdev->ops->read_resources(curdev);
 
 		/* Read in the resources behind the current device's links. */
-		for (link = curdev->link_list; link; link = link->next)
-			read_resources(link);
+		if (curdev->link_list)
+			read_resources(curdev->link_list);
 	}
 	post_log_clear();
-	printk(BIOS_SPEW, "%s %s segment group %d bus %d link: %d done\n",
-	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary, bus->link_num);
+	printk(BIOS_SPEW, "%s %s segment group %d bus %d done\n",
+	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary);
 }
 
 struct device *vga_pri = NULL;
@@ -301,8 +299,8 @@ void assign_resources(struct bus *bus)
 {
 	struct device *curdev;
 
-	printk(BIOS_SPEW, "%s %s, segment group %d bus %d link: %d\n",
-	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary, bus->link_num);
+	printk(BIOS_SPEW, "%s %s, segment group %d bus %d\n",
+	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary);
 
 	for (curdev = bus->children; curdev; curdev = curdev->sibling) {
 		if (!curdev->enabled || !curdev->resource_list)
@@ -317,8 +315,8 @@ void assign_resources(struct bus *bus)
 		curdev->ops->set_resources(curdev);
 	}
 	post_log_clear();
-	printk(BIOS_SPEW, "%s %s, segment group %d bus %d link: %d done\n",
-	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary, bus->link_num);
+	printk(BIOS_SPEW, "%s %s, segment group %d bus %d done\n",
+	       dev_path(bus->dev), __func__, bus->segment_group, bus->secondary);
 }
 
 /**
@@ -336,7 +334,6 @@ void assign_resources(struct bus *bus)
 static void enable_resources(struct bus *link)
 {
 	struct device *dev;
-	struct bus *c_link;
 
 	for (dev = link->children; dev; dev = dev->sibling) {
 		if (dev->enabled && dev->ops && dev->ops->enable_resources) {
@@ -346,8 +343,8 @@ static void enable_resources(struct bus *link)
 	}
 
 	for (dev = link->children; dev; dev = dev->sibling) {
-		for (c_link = dev->link_list; c_link; c_link = c_link->next)
-			enable_resources(c_link);
+		if (dev->link_list)
+			enable_resources(dev->link_list);
 	}
 	post_log_clear();
 }
@@ -394,17 +391,15 @@ static void scan_bus(struct device *busdev)
 
 	do_scan_bus = 1;
 	while (do_scan_bus) {
-		struct bus *link;
+		struct bus *link = busdev->link_list;
 		busdev->ops->scan_bus(busdev);
 		do_scan_bus = 0;
-		for (link = busdev->link_list; link; link = link->next) {
-			if (link->reset_needed) {
-				if (reset_bus(link))
-					do_scan_bus = 1;
-				else
-					busdev->bus->reset_needed = 1;
-			}
-		}
+		if (!link || !link->reset_needed)
+			continue;
+		if (reset_bus(link))
+			do_scan_bus = 1;
+		else
+			busdev->bus->reset_needed = 1;
 	}
 
 	scan_time = stopwatch_duration_msecs(&sw);
@@ -523,13 +518,11 @@ void dev_configure(void)
  */
 void dev_enable(void)
 {
-	struct bus *link;
-
 	printk(BIOS_INFO, "Enabling resources...\n");
 
 	/* Now enable everything. */
-	for (link = dev_root.link_list; link; link = link->next)
-		enable_resources(link);
+	if (dev_root.link_list)
+		enable_resources(dev_root.link_list);
 
 	printk(BIOS_INFO, "done.\n");
 }
@@ -553,8 +546,7 @@ static void init_dev(struct device *dev)
 		long init_time;
 
 		if (dev->path.type == DEVICE_PATH_I2C) {
-			printk(BIOS_DEBUG, "smbus: %s[%d]->",
-			       dev_path(dev->bus->dev), dev->bus->link_num);
+			printk(BIOS_DEBUG, "smbus: %s->", dev_path(dev->bus->dev));
 		}
 
 		printk(BIOS_DEBUG, "%s init\n", dev_path(dev));
@@ -572,7 +564,6 @@ static void init_dev(struct device *dev)
 static void init_link(struct bus *link)
 {
 	struct device *dev;
-	struct bus *c_link;
 
 	for (dev = link->children; dev; dev = dev->sibling) {
 		post_code(POSTCODE_BS_DEV_INIT);
@@ -580,10 +571,9 @@ static void init_link(struct bus *link)
 		init_dev(dev);
 	}
 
-	for (dev = link->children; dev; dev = dev->sibling) {
-		for (c_link = dev->link_list; c_link; c_link = c_link->next)
-			init_link(c_link);
-	}
+	for (dev = link->children; dev; dev = dev->sibling)
+		if (dev->link_list)
+			init_link(dev->link_list);
 }
 
 /**
@@ -594,16 +584,14 @@ static void init_link(struct bus *link)
  */
 void dev_initialize(void)
 {
-	struct bus *link;
-
 	printk(BIOS_INFO, "Initializing devices...\n");
 
 	/* First call the mainboard init. */
 	init_dev(&dev_root);
 
 	/* Now initialize everything. */
-	for (link = dev_root.link_list; link; link = link->next)
-		init_link(link);
+	if (dev_root.link_list)
+		init_link(dev_root.link_list);
 	post_log_clear();
 
 	printk(BIOS_INFO, "Devices initialized\n");
@@ -633,15 +621,13 @@ static void final_dev(struct device *dev)
 static void final_link(struct bus *link)
 {
 	struct device *dev;
-	struct bus *c_link;
 
 	for (dev = link->children; dev; dev = dev->sibling)
 		final_dev(dev);
 
-	for (dev = link->children; dev; dev = dev->sibling) {
-		for (c_link = dev->link_list; c_link; c_link = c_link->next)
-			final_link(c_link);
-	}
+	for (dev = link->children; dev; dev = dev->sibling)
+		if (dev->link_list)
+			final_link(dev->link_list);
 }
 /**
  * Finalize all devices in the global device tree.
@@ -651,16 +637,13 @@ static void final_link(struct bus *link)
  */
 void dev_finalize(void)
 {
-	struct bus *link;
-
 	printk(BIOS_INFO, "Finalize devices...\n");
 
 	/* First call the mainboard finalize. */
 	final_dev(&dev_root);
 
 	/* Now finalize everything. */
-	for (link = dev_root.link_list; link; link = link->next)
-		final_link(link);
+	final_link(dev_root.link_list);
 
 	printk(BIOS_INFO, "Devices finalized\n");
 }
diff --git a/src/device/device_util.c b/src/device/device_util.c
index 260c9b43eedc..ea4ef27f9f0b 100644
--- a/src/device/device_util.c
+++ b/src/device/device_util.c
@@ -560,16 +560,9 @@ void search_bus_resources(struct bus *bus, unsigned long type_mask,
 
 			/* If it is a subtractive resource recurse. */
 			if (res->flags & IORESOURCE_SUBTRACTIVE) {
-				struct bus *subbus;
-				for (subbus = curdev->link_list; subbus;
-				     subbus = subbus->next)
-					if (subbus->link_num
-					== IOINDEX_SUBTRACTIVE_LINK(res->index))
-						break;
-				if (!subbus) /* Why can subbus be NULL?  */
-					break;
-				search_bus_resources(subbus, type_mask, type,
-						     search, gp);
+				if (curdev->link_list)
+					search_bus_resources(curdev->link_list, type_mask, type,
+							     search, gp);
 				continue;
 			}
 			search(gp, curdev, res);
@@ -624,9 +617,8 @@ void disable_children(struct bus *bus)
 	struct device *child;
 
 	for (child = bus->children; child; child = child->sibling) {
-		struct bus *link;
-		for (link = child->link_list; link; link = link->next)
-			disable_children(link);
+		if (child->link_list)
+			disable_children(child->link_list);
 		dev_set_enabled(child, 0);
 	}
 }
@@ -637,7 +629,6 @@ void disable_children(struct bus *bus)
  */
 bool dev_is_active_bridge(struct device *dev)
 {
-	struct bus *link;
 	struct device *child;
 
 	if (!dev || !dev->enabled)
@@ -646,71 +637,20 @@ bool dev_is_active_bridge(struct device *dev)
 	if (!dev->link_list || !dev->link_list->children)
 		return 0;
 
-	for (link = dev->link_list; link; link = link->next) {
-		for (child = link->children; child; child = child->sibling) {
-			if (child->path.type == DEVICE_PATH_NONE)
-				continue;
-
-			if (child->enabled)
-				return 1;
-		}
+	for (child = dev->link_list->children; child; child = child->sibling) {
+		if (child->path.type == DEVICE_PATH_NONE)
+			continue;
+		if (child->enabled)
+			return 1;
 	}
 
 	return 0;
 }
 
-/**
- * Ensure the device has a minimum number of bus links.
- *
- * @param dev The device to add links to.
- * @param total_links The minimum number of links to have.
- */
-void add_more_links(struct device *dev, unsigned int total_links)
-{
-	struct bus *link, *last = NULL;
-	int link_num = -1;
-
-	for (link = dev->link_list; link; link = link->next) {
-		if (link_num < link->link_num)
-			link_num = link->link_num;
-		last = link;
-	}
-
-	if (last) {
-		int links = total_links - (link_num + 1);
-		if (links > 0) {
-			link = malloc(links * sizeof(*link));
-			if (!link)
-				die("Couldn't allocate more links!\n");
-			memset(link, 0, links * sizeof(*link));
-			last->next = link;
-		} else {
-			/* No more links to add */
-			return;
-		}
-	} else {
-		link = malloc(total_links * sizeof(*link));
-		if (!link)
-			die("Couldn't allocate more links!\n");
-		memset(link, 0, total_links * sizeof(*link));
-		dev->link_list = link;
-	}
-
-	for (link_num = link_num + 1; link_num < total_links; link_num++) {
-		link->link_num = link_num;
-		link->dev = dev;
-		link->next = link + 1;
-		last = link;
-		link = link->next;
-	}
-	last->next = NULL;
-}
-
 static void resource_tree(const struct device *root, int debug_level, int depth)
 {
 	int i = 0;
 	struct device *child;
-	struct bus *link;
 	struct resource *res;
 	char indent[30];	/* If your tree has more levels, it's wrong. */
 
@@ -732,10 +672,11 @@ static void resource_tree(const struct device *root, int debug_level, int depth)
 			  res->index);
 	}
 
-	for (link = root->link_list; link; link = link->next) {
-		for (child = link->children; child; child = child->sibling)
-			resource_tree(child, debug_level, depth + 1);
-	}
+	if (!root->link_list)
+		return;
+
+	for (child = root->link_list->children; child; child = child->sibling)
+		resource_tree(child, debug_level, depth + 1);
 }
 
 void print_resource_tree(const struct device *root, int debug_level,
@@ -760,7 +701,6 @@ void show_devs_tree(const struct device *dev, int debug_level, int depth)
 	char depth_str[20];
 	int i;
 	struct device *sibling;
-	struct bus *link;
 
 	for (i = 0; i < depth; i++)
 		depth_str[i] = ' ';
@@ -769,11 +709,11 @@ void show_devs_tree(const struct device *dev, int debug_level, int depth)
 	printk(debug_level, "%s%s: enabled %d\n",
 		  depth_str, dev_path(dev), dev->enabled);
 
-	for (link = dev->link_list; link; link = link->next) {
-		for (sibling = link->children; sibling;
-		     sibling = sibling->sibling)
-			show_devs_tree(sibling, debug_level, depth + 1);
-	}
+	if (!dev->link_list)
+		return;
+
+	for (sibling = dev->link_list->children; sibling; sibling = sibling->sibling)
+		show_devs_tree(sibling, debug_level, depth + 1);
 }
 
 void show_all_devs_tree(int debug_level, const char *msg)
diff --git a/src/device/pci_device.c b/src/device/pci_device.c
index acdad421c536..24b95238f134 100644
--- a/src/device/pci_device.c
+++ b/src/device/pci_device.c
@@ -713,16 +713,13 @@ static void pci_set_resource(struct device *dev, struct resource *resource)
 void pci_dev_set_resources(struct device *dev)
 {
 	struct resource *res;
-	struct bus *bus;
 	u8 line;
 
 	for (res = dev->resource_list; res; res = res->next)
 		pci_set_resource(dev, res);
 
-	for (bus = dev->link_list; bus; bus = bus->next) {
-		if (bus->children)
-			assign_resources(bus);
-	}
+	if (dev->link_list && dev->link_list->children)
+		assign_resources(dev->link_list);
 
 	/* Set a default latency timer. */
 	pci_write_config8(dev, PCI_LATENCY_TIMER, 0x40);
diff --git a/src/device/root_device.c b/src/device/root_device.c
index d8edbd58bbe3..54e82ea602ed 100644
--- a/src/device/root_device.c
+++ b/src/device/root_device.c
@@ -38,31 +38,27 @@ void enable_static_device(struct device *dev)
 void enable_static_devices(struct device *bus)
 {
 	struct device *child;
-	struct bus *link;
 
-	for (link = bus->link_list; link; link = link->next) {
-		for (child = link->children; child; child = child->sibling) {
-			enable_static_device(child);
-		}
-	}
+	if (!bus->link_list)
+		return;
+
+	for (child = bus->link_list->children; child; child = child->sibling)
+		enable_static_device(child);
 }
 
 void scan_generic_bus(struct device *bus)
 {
 	struct device *child;
-	struct bus *link;
 	static int bus_max = 0;
 
 	printk(BIOS_SPEW, "%s for %s\n", __func__, dev_path(bus));
 
-	for (link = bus->link_list; link; link = link->next) {
-
-		link->secondary = ++bus_max;
+	if (bus->link_list) {
+		bus->link_list->secondary = ++bus_max;
 
-		for (child = link->children; child; child = child->sibling) {
+		for (child = bus->link_list->children; child; child = child->sibling) {
 			enable_static_device(child);
-			printk(BIOS_DEBUG, "bus: %s[%d]->", dev_path(child->bus->dev),
-			       child->bus->link_num);
+			printk(BIOS_DEBUG, "bus: %s->", dev_path(child->bus->dev));
 		}
 	}
 
@@ -86,14 +82,12 @@ void scan_smbus(struct device *bus)
  */
 void scan_static_bus(struct device *bus)
 {
-	struct bus *link;
-
 	printk(BIOS_SPEW, "%s for %s\n", __func__, dev_path(bus));
 
 	enable_static_devices(bus);
 
-	for (link = bus->link_list; link; link = link->next)
-		scan_bridges(link);
+	if (bus->link_list)
+		scan_bridges(bus->link_list);
 
 	printk(BIOS_SPEW, "%s for %s done\n", __func__, dev_path(bus));
 }
diff --git a/src/include/device/device.h b/src/include/device/device.h
index 13bc8dcb346e..b7917e369379 100644
--- a/src/include/device/device.h
+++ b/src/include/device/device.h
@@ -4,11 +4,13 @@
 
 #define DEVICE_H
 
-#include <device/resource.h>
+#include <console/console.h>
 #include <device/path.h>
 #include <device/pci_type.h>
+#include <device/resource.h>
 #include <smbios.h>
 #include <static.h>
+#include <stdlib.h>
 #include <types.h>
 
 struct fw_config;
@@ -78,10 +80,8 @@ static inline void noop_set_resources(struct device *dev) {}
 struct bus {
 	DEVTREE_CONST struct device *dev;	/* This bridge device */
 	DEVTREE_CONST struct device *children;	/* devices behind this bridge */
-	DEVTREE_CONST struct bus *next;		/* The next bridge on this device */
 	unsigned int	bridge_ctrl;		/* Bridge control register */
 	uint16_t	bridge_cmd;		/* Bridge command register */
-	unsigned char	link_num;		/* The index of this link */
 	uint16_t	secondary;		/* secondary bus number */
 	uint16_t	subordinate;		/* subordinate bus number */
 	uint16_t	max_subordinate;	/* max subordinate bus number */
@@ -193,7 +193,6 @@ struct device *dev_get_pci_domain(struct device *dev);
 void dev_set_enabled(struct device *dev, int enable);
 void disable_children(struct bus *bus);
 bool dev_is_active_bridge(struct device *dev);
-void add_more_links(struct device *dev, unsigned int total_links);
 bool is_dev_enabled(const struct device *const dev);
 bool is_devfn_enabled(unsigned int devfn);
 bool is_cpu(const struct device *cpu);
diff --git a/src/northbridge/amd/pi/00730F01/northbridge.c b/src/northbridge/amd/pi/00730F01/northbridge.c
index a4409fb0df38..5e82ccd51c98 100644
--- a/src/northbridge/amd/pi/00730F01/northbridge.c
+++ b/src/northbridge/amd/pi/00730F01/northbridge.c
@@ -235,7 +235,6 @@ static void add_ivhd_device_entries(struct device *parent, struct device *dev,
 				    unsigned long *current, uint16_t *ivhd_length)
 {
 	struct device *sibling;
-	struct bus *link;
 
 	if (!root_level) {
 		root_level = malloc(sizeof(int8_t));
@@ -254,11 +253,11 @@ static void add_ivhd_device_entries(struct device *parent, struct device *dev,
 		}
 	}
 
-	for (link = dev->link_list; link; link = link->next)
-		for (sibling = link->children; sibling; sibling =
-		     sibling->sibling)
+	if (dev->link_list) {
+		for (sibling = dev->link_list->children; sibling; sibling = sibling->sibling)
 			add_ivhd_device_entries(dev, sibling, depth + 1, depth, root_level,
 						current, ivhd_length);
+	}
 
 	free(root_level);
 }
diff --git a/src/soc/amd/common/block/acpi/ivrs.c b/src/soc/amd/common/block/acpi/ivrs.c
index 9d0ece1d6ca9..57b5974e71da 100644
--- a/src/soc/amd/common/block/acpi/ivrs.c
+++ b/src/soc/amd/common/block/acpi/ivrs.c
@@ -140,7 +140,6 @@ static void add_ivhd_device_entries(struct device *parent, struct device *dev,
 				    unsigned long *current, uint16_t nb_bus)
 {
 	struct device *sibling;
-	struct bus *link;
 
 	if (!root_level)
 		return;
@@ -155,11 +154,11 @@ static void add_ivhd_device_entries(struct device *parent, struct device *dev,
 				ivrs_add_device_or_bridge(parent, dev, current);
 	}
 
-	for (link = dev->link_list; link; link = link->next)
-		for (sibling = link->children; sibling; sibling =
-		     sibling->sibling)
-			add_ivhd_device_entries(dev, sibling, depth + 1, depth, root_level,
-						current, nb_bus);
+	if (!dev->link_list)
+		return;
+	for (sibling = dev->link_list->children; sibling; sibling = sibling->sibling)
+		add_ivhd_device_entries(dev, sibling, depth + 1, depth, root_level, current,
+					nb_bus);
 }
 
 static unsigned long acpi_ivhd_misc(unsigned long current, struct device *dev)
diff --git a/src/soc/amd/common/block/lpc/lpc.c b/src/soc/amd/common/block/lpc/lpc.c
index 4e8131688123..c07636108050 100644
--- a/src/soc/amd/common/block/lpc/lpc.c
+++ b/src/soc/amd/common/block/lpc/lpc.c
@@ -278,20 +278,20 @@ static void configure_child_espi_windows(struct device *child)
 
 static void lpc_enable_children_resources(struct device *dev)
 {
-	struct bus *link;
 	struct device *child;
 
-	for (link = dev->link_list; link; link = link->next) {
-		for (child = link->children; child; child = child->sibling) {
-			if (!child->enabled)
-				continue;
-			if (child->path.type != DEVICE_PATH_PNP)
-				continue;
-			if (CONFIG(SOC_AMD_COMMON_BLOCK_USE_ESPI))
-				configure_child_espi_windows(child);
-			else
-				configure_child_lpc_windows(dev, child);
-		}
+	if (!dev->link_list)
+		return;
+
+	for (child = dev->link_list->children; child; child = child->sibling) {
+		if (!child->enabled)
+			continue;
+		if (child->path.type != DEVICE_PATH_PNP)
+			continue;
+		if (CONFIG(SOC_AMD_COMMON_BLOCK_USE_ESPI))
+			configure_child_espi_windows(child);
+		else
+			configure_child_lpc_windows(dev, child);
 	}
 }
 
diff --git a/src/soc/amd/stoneyridge/northbridge.c b/src/soc/amd/stoneyridge/northbridge.c
index deebfb351fde..b95c4cdf2e8d 100644
--- a/src/soc/amd/stoneyridge/northbridge.c
+++ b/src/soc/amd/stoneyridge/northbridge.c
@@ -52,16 +52,9 @@ static void read_resources(struct device *dev)
 
 static void create_vga_resource(struct device *dev)
 {
-	struct bus *link;
-
-	/* find out which link the VGA card is connected,
-	 * we only deal with the 'first' vga card */
-	for (link = dev->link_list ; link ; link = link->next)
-		if (link->bridge_ctrl & PCI_BRIDGE_CTL_VGA)
-			break;
-
-	/* no VGA card installed */
-	if (link == NULL)
+	if (!dev->link_list)
+		return;
+	if (!(dev->link_list->bridge_ctrl & PCI_BRIDGE_CTL_VGA))
 		return;
 
 	printk(BIOS_DEBUG, "VGA: %s has VGA device\n",	dev_path(dev));
@@ -71,14 +64,11 @@ static void create_vga_resource(struct device *dev)
 
 static void set_resources(struct device *dev)
 {
-	struct bus *bus;
-
 	/* do we need this? */
 	create_vga_resource(dev);
 
-	for (bus = dev->link_list ; bus ; bus = bus->next)
-		if (bus->children)
-			assign_resources(bus);
+	if (dev->link_list && dev->link_list->children)
+		assign_resources(dev->link_list);
 }
 
 static void northbridge_init(struct device *dev)
diff --git a/src/soc/intel/common/block/lpc/lpc.c b/src/soc/intel/common/block/lpc/lpc.c
index 6d3b90f690a9..994ef9bcb82b 100644
--- a/src/soc/intel/common/block/lpc/lpc.c
+++ b/src/soc/intel/common/block/lpc/lpc.c
@@ -100,13 +100,13 @@ static void pch_lpc_loop_resources(struct device *dev)
  */
 static void pch_lpc_set_child_resources(struct device *dev)
 {
-	struct bus *link;
 	struct device *child;
 
-	for (link = dev->link_list; link; link = link->next) {
-		for (child = link->children; child; child = child->sibling)
-			pch_lpc_loop_resources(child);
-	}
+	if (!dev->link_list)
+		return;
+
+	for (child = dev->link_list->children; child; child = child->sibling)
+		pch_lpc_loop_resources(child);
 }
 
 static void pch_lpc_set_resources(struct device *dev)
diff --git a/src/southbridge/amd/pi/hudson/lpc.c b/src/southbridge/amd/pi/hudson/lpc.c
index 0a4e03838587..266d75c58945 100644
--- a/src/southbridge/amd/pi/hudson/lpc.c
+++ b/src/southbridge/amd/pi/hudson/lpc.c
@@ -134,7 +134,6 @@ static void hudson_lpc_set_resources(struct device *dev)
  */
 static void hudson_lpc_enable_childrens_resources(struct device *dev)
 {
-	struct bus *link;
 	u32 reg, reg_x;
 	int var_num = 0;
 	u16 reg_var[3];
@@ -171,12 +170,10 @@ static void hudson_lpc_enable_childrens_resources(struct device *dev)
 	reg_var[1] = pci_read_config16(dev, 0x66);
 	reg_var[0] = pci_read_config16(dev, 0x64);
 
-	for (link = dev->link_list; link; link = link->next) {
-		struct device *child;
-		for (child = link->children; child;
-		     child = child->sibling) {
-			if (child->enabled
-			    && (child->path.type == DEVICE_PATH_PNP)) {
+	struct device *child;
+	if (dev->link_list) {
+		for (child = dev->link_list->children; child; child = child->sibling) {
+			if (child->enabled && (child->path.type == DEVICE_PATH_PNP)) {
 				struct resource *res;
 				for (res = child->resource_list; res; res = res->next) {
 					u32 base, end;	/*  don't need long long */
diff --git a/util/sconfig/main.c b/util/sconfig/main.c
index dd26e07de84d..533c9fbb1854 100644
--- a/util/sconfig/main.c
+++ b/util/sconfig/main.c
@@ -81,7 +81,6 @@ static struct device override_root_dev;
 static struct chip_instance mainboard_instance;
 
 static struct bus base_root_bus = {
-	.id = 0,
 	.dev = &base_root_dev,
 };
 
@@ -95,7 +94,6 @@ static struct device base_root_dev = {
 };
 
 static struct bus chipset_root_bus = {
-	.id = 0,
 	.dev = &chipset_root_dev,
 };
 
@@ -109,7 +107,6 @@ static struct device chipset_root_dev = {
 };
 
 static struct bus override_root_bus = {
-	.id = 0,
 	.dev = &override_root_dev,
 };
 
@@ -723,30 +720,13 @@ void add_device_ops(struct bus *bus, char *ops_id)
 	bus->dev->ops_id = ops_id;
 }
 
-/*
- * Allocate a new bus for the provided device.
- *   - If this is the first bus being allocated under this device, then its id
- *     is set to 0 and bus and last_bus are pointed to the newly allocated bus.
- *   - If this is not the first bus under this device, then its id is set to 1
- *     plus the id of last bus and newly allocated bus is added to the list of
- *     buses under the device. last_bus is updated to point to the newly
- *     allocated bus.
- */
+/* Allocate a new bus for the provided device. */
 static void alloc_bus(struct device *dev)
 {
 	struct bus *bus = S_ALLOC(sizeof(*bus));
 
 	bus->dev = dev;
-
-	if (dev->last_bus == NULL)  {
-		bus->id = 0;
-		dev->bus = bus;
-	} else {
-		bus->id = dev->last_bus->id + 1;
-		dev->last_bus->next_bus = bus;
-	}
-
-	dev->last_bus = bus;
+	dev->bus = bus;
 }
 
 /*
@@ -814,14 +794,15 @@ static const struct device *find_alias(const struct device *const parent,
 	if (parent->alias && !strcmp(parent->alias, alias))
 		return parent;
 
-	const struct bus *bus;
-	for (bus = parent->bus; bus; bus = bus->next_bus) {
-		const struct device *child;
-		for (child = bus->children; child; child = child->sibling) {
-			const struct device *const ret = find_alias(child, alias);
-			if (ret)
-				return ret;
-		}
+	const struct bus *bus = parent->bus;
+	if (!bus)
+		return NULL;
+
+	const struct device *child;
+	for (child = bus->children; child; child = child->sibling) {
+		const struct device *const ret = find_alias(child, alias);
+		if (ret)
+			return ret;
 	}
 
 	return NULL;
@@ -834,11 +815,11 @@ static struct device *new_device_with_path(struct bus *parent,
 {
 	struct device *new_d;
 
-	/* If device is found under parent, no need to allocate new device. */
+	/* We don't allow duplicate devices in devicetree. */
 	new_d = get_dev(parent, path_a, path_b, bustype, chip_instance);
 	if (new_d) {
-		alloc_bus(new_d);
-		return new_d;
+		printf("ERROR: Duplicate device! %s\n", new_d->name);
+		exit(1);
 	}
 
 	new_d = alloc_dev(parent);
@@ -1084,11 +1065,8 @@ static int dev_has_children(struct device *dev)
 {
 	struct bus *bus = dev->bus;
 
-	while (bus) {
-		if (bus->children)
-			return 1;
-		bus = bus->next_bus;
-	}
+	if (bus && bus->children)
+		return 1;
 
 	return 0;
 }
@@ -1098,7 +1076,7 @@ static void pass0(FILE *fil, FILE *head, struct device *ptr, struct device *next
 	static int dev_id;
 
 	if (ptr == &base_root_dev) {
-		fprintf(fil, "STORAGE struct bus %s_links[];\n",
+		fprintf(fil, "STORAGE struct bus %s_bus;\n",
 			ptr->name);
 		return;
 	}
@@ -1120,7 +1098,7 @@ static void pass0(FILE *fil, FILE *head, struct device *ptr, struct device *next
 		fprintf(fil, "STORAGE struct resource %s_res[];\n",
 			ptr->name);
 	if (dev_has_children(ptr))
-		fprintf(fil, "STORAGE struct bus %s_links[];\n",
+		fprintf(fil, "STORAGE struct bus %s_bus;\n",
 			ptr->name);
 
 	if (next)
@@ -1192,35 +1170,18 @@ static void emit_resources(FILE *fil, struct device *ptr)
 	fprintf(fil, "\t };\n");
 }
 
-static void emit_bus(FILE *fil, struct bus *bus)
+static void emit_dev_bus(FILE *fil, struct device *ptr)
 {
-	fprintf(fil, "\t\t[%d] = {\n", bus->id);
-	fprintf(fil, "\t\t\t.link_num = %d,\n", bus->id);
-	fprintf(fil, "\t\t\t.dev = &%s,\n", bus->dev->name);
-	if (bus->children)
-		fprintf(fil, "\t\t\t.children = &%s,\n", bus->children->name);
-
-	if (bus->next_bus)
-		fprintf(fil, "\t\t\t.next=&%s_links[%d],\n", bus->dev->name,
-			bus->id + 1);
-	else
-		fprintf(fil, "\t\t\t.next = NULL,\n");
-	fprintf(fil, "\t\t},\n");
-}
-
-static void emit_dev_links(FILE *fil, struct device *ptr)
-{
-	fprintf(fil, "STORAGE struct bus %s_links[] = {\n",
+	fprintf(fil, "STORAGE struct bus %s_bus = {\n",
 		ptr->name);
 
+	assert(ptr->bus && ptr->bus->children);
 	struct bus *bus = ptr->bus;
 
-	while (bus) {
-		emit_bus(fil, bus);
-		bus = bus->next_bus;
-	}
+	fprintf(fil, "\t.dev = &%s,\n", bus->dev->name);
+	fprintf(fil, "\t.children = &%s,\n", bus->children->name);
 
-	fprintf(fil, "\t};\n");
+	fprintf(fil, "};\n");
 }
 
 static struct chip_instance *get_chip_instance(const struct device *dev)
@@ -1268,8 +1229,7 @@ static void pass1(FILE *fil, FILE *head, struct device *ptr, struct device *next
 	else
 		fprintf(fil, "\t.ops = NULL,\n");
 	fprintf(fil, "#endif\n");
-	fprintf(fil, "\t.bus = &%s_links[%d],\n", ptr->parent->dev->name,
-		ptr->parent->id);
+	fprintf(fil, "\t.bus = &%s_bus,\n", ptr->parent->dev->name);
 	fprintf(fil, "\t.path = {");
 	fprintf(fil, ptr->path, ptr->path_a, ptr->path_b);
 	fprintf(fil, "},\n");
@@ -1290,7 +1250,7 @@ static void pass1(FILE *fil, FILE *head, struct device *ptr, struct device *next
 			ptr->name);
 	}
 	if (has_children)
-		fprintf(fil, "\t.link_list = &%s_links[0],\n",
+		fprintf(fil, "\t.link_list = &%s_bus,\n",
 			ptr->name);
 	else
 		fprintf(fil, "\t.link_list = NULL,\n");
@@ -1319,7 +1279,7 @@ static void pass1(FILE *fil, FILE *head, struct device *ptr, struct device *next
 	emit_resources(fil, ptr);
 
 	if (has_children)
-		emit_dev_links(fil, ptr);
+		emit_dev_bus(fil, ptr);
 }
 
 static void expose_device_names(FILE *fil, FILE *head, struct device *ptr, struct device *next)
@@ -1370,11 +1330,8 @@ static void add_children_to_queue(struct queue_entry **bfs_q_head,
 {
 	struct bus *bus = d->bus;
 
-	while (bus) {
-		if (bus->children)
-			add_siblings_to_queue(bfs_q_head, bus->children);
-		bus = bus->next_bus;
-	}
+	if (dev_has_children(d))
+		add_siblings_to_queue(bfs_q_head, bus->children);
 }
 
 static void walk_device_tree(FILE *fil, FILE *head, struct device *ptr,
@@ -1724,12 +1681,9 @@ static void override_devicetree(struct bus *base_parent,
  * +-----------------------------------------------------------------+
  * |                    |                                            |
  * | bus                | Recursively call override_devicetree on    |
- * | last_bus           | each bus of override device. It is assumed |
+ * |                    | each bus of override device. It is assumed |
  * |                    | that bus with id X under base device       |
- * |                    | to bus with id X under override device. If |
- * |                    | override device has more buses than base   |
- * |                    | device, then new buses are allocated under |
- * |                    | base device.                               |
+ * |                    | to bus with id X under override device.    |
  * |                    |                                            |
  * +-----------------------------------------------------------------+
  */
@@ -1841,29 +1795,20 @@ static void update_device(struct device *base_dev, struct device *override_dev)
 	/*
 	 * Now that the device properties are all copied over, look at each bus
 	 * of the override device and run override_devicetree in a recursive
-	 * manner. The assumption here is that first bus of override device
-	 * corresponds to first bus of base device and so on. If base device has
-	 * lesser buses than override tree, then new buses are allocated for it.
+	 * manner. If base device has no bus but the override tree has, then a new
+	 * bus is allocated for it.
 	 */
 	struct bus *override_bus = override_dev->bus;
 	struct bus *base_bus = base_dev->bus;
 
-	while (override_bus) {
-
-		/*
-		 * If we have more buses in override tree device, then allocate
-		 * a new bus for the base tree device as well.
-		 */
-		if (!base_bus) {
-			alloc_bus(base_dev);
-			base_bus = base_dev->last_bus;
-		}
-
-		override_devicetree(base_dev->bus, override_dev->bus);
+	/*
+	 * If we have more buses in override tree device, then allocate
+	 * a new bus for the base tree device as well.
+	 */
+	if (!base_bus)
+		alloc_bus(base_dev);
 
-		override_bus = override_bus->next_bus;
-		base_bus = base_bus->next_bus;
-	}
+	override_devicetree(base_dev->bus, override_dev->bus);
 }
 
 /*
diff --git a/util/sconfig/sconfig.h b/util/sconfig/sconfig.h
index cb8f7b36eff2..bb9a98f268b9 100644
--- a/util/sconfig/sconfig.h
+++ b/util/sconfig/sconfig.h
@@ -106,17 +106,11 @@ struct chip {
 
 struct device;
 struct bus {
-	/* Instance/ID of the bus under the device. */
-	int id;
-
 	/* Pointer to device to which this bus belongs. */
 	struct device *dev;
 
 	/* Pointer to list of children. */
 	struct device *children;
-
-	/* Pointer to next bus for the device. */
-	struct bus *next_bus;
 };
 
 struct device {
@@ -157,10 +151,8 @@ struct device {
 	/* Pointer to chip instance for this device. */
 	struct chip_instance *chip_instance;
 
-	/* Pointer to list of buses under this device. */
+	/* Pointer to the bus under this device. */
 	struct bus *bus;
-	/* Pointer to last bus under this device. */
-	struct bus *last_bus;
 
 	/* Global identifier of the ops for this device. */
 	char *ops_id;
diff --git a/util/sconfig/sconfig.tab.c_shipped b/util/sconfig/sconfig.tab.c_shipped
index cb60fb59a74b..5b10922a896d 100644
--- a/util/sconfig/sconfig.tab.c_shipped
+++ b/util/sconfig/sconfig.tab.c_shipped
@@ -1238,7 +1238,7 @@ yyreduce:
   case 26: /* @2: %empty  */
                                                        {
 	(yyval.dev) = new_device_raw(cur_parent, cur_chip_instance, (yyvsp[-3].number), (yyvsp[-2].string), (yyvsp[-1].string), (yyvsp[0].number));
-	cur_parent = (yyval.dev)->last_bus;
+	cur_parent = (yyval.dev)->bus;
 }
     break;
 
@@ -1251,7 +1251,7 @@ yyreduce:
   case 28: /* @3: %empty  */
                                        {
 	(yyval.dev) = new_device_reference(cur_parent, cur_chip_instance, (yyvsp[-1].string), (yyvsp[0].number));
-	cur_parent = (yyval.dev)->last_bus;
+	cur_parent = (yyval.dev)->bus;
 }
     break;
 
diff --git a/util/sconfig/sconfig.y b/util/sconfig/sconfig.y
index 17ab9a58396d..8ec103c018ef 100644
--- a/util/sconfig/sconfig.y
+++ b/util/sconfig/sconfig.y
@@ -44,7 +44,7 @@ chip: CHIP STRING /* == path */ {
 
 device: DEVICE BUS NUMBER /* == devnum */ alias status {
 	$<dev>$ = new_device_raw(cur_parent, cur_chip_instance, $<number>2, $<string>3, $<string>4, $<number>5);
-	cur_parent = $<dev>$->last_bus;
+	cur_parent = $<dev>$->bus;
 }
 	devicechildren END {
 	cur_parent = $<dev>6->parent;
@@ -52,7 +52,7 @@ device: DEVICE BUS NUMBER /* == devnum */ alias status {
 
 device: DEVICE REFERENCE STRING status {
 	$<dev>$ = new_device_reference(cur_parent, cur_chip_instance, $<string>3, $<number>4);
-	cur_parent = $<dev>$->last_bus;
+	cur_parent = $<dev>$->bus;
 }
 	devicechildren END {
 	cur_parent = $<dev>5->parent;