PCI: Move CardBus bridge scanning to setup-cardbus.c

The PCI core's pci_scan_bridge_extend() contains convoluted logic specific
to setting up bus numbers for legacy CardBus bridges. Extract the CardBus
specific part out into setup-cardbus.c to make the core code cleaner and
allow omitting CardBus bridge support from modern systems.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251219174036.16738-24-ilpo.jarvinen@linux.intel.com

drivers/pci/pci.h

@@ -242,6 +242,7 @@ void pci_config_pm_runtime_put(struct pci_dev *dev);
 void pci_pm_power_up_and_verify_state(struct pci_dev *pci_dev);
 void pci_pm_init(struct pci_dev *dev);
 void pci_ea_init(struct pci_dev *dev);
+bool pci_ea_fixed_busnrs(struct pci_dev *dev, u8 *sec, u8 *sub);
 void pci_msi_init(struct pci_dev *dev);
 void pci_msix_init(struct pci_dev *dev);
 bool pci_bridge_d3_possible(struct pci_dev *dev);
@@ -377,10 +378,17 @@ extern unsigned long pci_hotplug_mmio_size;
 extern unsigned long pci_hotplug_mmio_pref_size;
 extern unsigned long pci_hotplug_bus_size;
 
+static inline bool pci_is_cardbus_bridge(struct pci_dev *dev)
+{
+	return dev->hdr_type == PCI_HEADER_TYPE_CARDBUS;
+}
 #ifdef CONFIG_CARDBUS
 unsigned long pci_cardbus_resource_alignment(struct resource *res);
 int pci_bus_size_cardbus_bridge(struct pci_bus *bus,
 				struct list_head *realloc_head);
+int pci_cardbus_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
+				   u32 buses, int max,
+				   unsigned int available_buses, int pass);
 int pci_setup_cardbus(char *str);
 
 #else
@@ -393,6 +401,14 @@ static inline int pci_bus_size_cardbus_bridge(struct pci_bus *bus,
 {
 	return -EOPNOTSUPP;
 }
+static inline int pci_cardbus_scan_bridge_extend(struct pci_bus *bus,
+						 struct pci_dev *dev,
+						 u32 buses, int max,
+						 unsigned int available_buses,
+						 int pass)
+{
+	return max;
+}
 static inline int pci_setup_cardbus(char *str) { return -ENOENT; }
 #endif /* CONFIG_CARDBUS */
 

drivers/pci/probe.c

@@ -25,9 +25,6 @@
 #include <linux/bitfield.h>
 #include "pci.h"
 
-#define CARDBUS_LATENCY_TIMER	176	/* secondary latency timer */
-#define CARDBUS_RESERVE_BUSNR	3
-
 static struct resource busn_resource = {
 	.name	= "PCI busn",
 	.start	= 0,
@@ -1343,7 +1340,7 @@ void pbus_validate_busn(struct pci_bus *bus)
  * and subordinate bus numbers, return true with the bus numbers in @sec
  * and @sub.  Otherwise return false.
  */
-static bool pci_ea_fixed_busnrs(struct pci_dev *dev, u8 *sec, u8 *sub)
+bool pci_ea_fixed_busnrs(struct pci_dev *dev, u8 *sec, u8 *sub)
 {
 	int ea, offset;
 	u32 dw;
@@ -1397,8 +1394,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 				  int pass)
 {
 	struct pci_bus *child;
-	int is_cardbus = (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS);
-	u32 buses, i, j = 0;
+	u32 buses;
 	u16 bctl;
 	u8 primary, secondary, subordinate;
 	int broken = 0;
@@ -1442,8 +1438,15 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 	pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
 			      bctl & ~PCI_BRIDGE_CTL_MASTER_ABORT);
 
-	if ((secondary || subordinate) && !pcibios_assign_all_busses() &&
-	    !is_cardbus && !broken) {
+	if (pci_is_cardbus_bridge(dev)) {
+		max = pci_cardbus_scan_bridge_extend(bus, dev, buses, max,
+						     available_buses,
+						     pass);
+		goto out;
+	}
+
+	if ((secondary || subordinate) &&
+	    !pcibios_assign_all_busses() && !broken) {
 		unsigned int cmax, buses;
 
 		/*
@@ -1485,7 +1488,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 		 * do in the second pass.
 		 */
 		if (!pass) {
-			if (pcibios_assign_all_busses() || broken || is_cardbus)
+			if (pcibios_assign_all_busses() || broken)
 
 				/*
 				 * Temporarily disable forwarding of the
@@ -1532,55 +1535,11 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			FIELD_PREP(PCI_SECONDARY_BUS_MASK, child->busn_res.start) |
 			FIELD_PREP(PCI_SUBORDINATE_BUS_MASK, child->busn_res.end);
 
-		/*
-		 * yenta.c forces a secondary latency timer of 176.
-		 * Copy that behaviour here.
-		 */
-		if (is_cardbus) {
-			buses &= ~PCI_SEC_LATENCY_TIMER_MASK;
-			buses |= FIELD_PREP(PCI_SEC_LATENCY_TIMER_MASK,
-					    CARDBUS_LATENCY_TIMER);
-		}
-
 		/* We need to blast all three values with a single write */
 		pci_write_config_dword(dev, PCI_PRIMARY_BUS, buses);
 
-		if (!is_cardbus) {
-			child->bridge_ctl = bctl;
-			max = pci_scan_child_bus_extend(child, available_buses);
-		} else {
-
-			/*
-			 * For CardBus bridges, we leave 4 bus numbers as
-			 * cards with a PCI-to-PCI bridge can be inserted
-			 * later.
-			 */
-			for (i = 0; i < CARDBUS_RESERVE_BUSNR; i++) {
-				struct pci_bus *parent = bus;
-				if (pci_find_bus(pci_domain_nr(bus),
-							max+i+1))
-					break;
-				while (parent->parent) {
-					if ((!pcibios_assign_all_busses()) &&
-					    (parent->busn_res.end > max) &&
-					    (parent->busn_res.end <= max+i)) {
-						j = 1;
-					}
-					parent = parent->parent;
-				}
-				if (j) {
-
-					/*
-					 * Often, there are two CardBus
-					 * bridges -- try to leave one
-					 * valid bus number for each one.
-					 */
-					i /= 2;
-					break;
-				}
-			}
-			max += i;
-		}
+		child->bridge_ctl = bctl;
+		max = pci_scan_child_bus_extend(child, available_buses);
 
 		/*
 		 * Set subordinate bus number to its real value.
@@ -1592,9 +1551,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 		pci_bus_update_busn_res_end(child, max);
 		pci_write_config_byte(dev, PCI_SUBORDINATE_BUS, max);
 	}
-
-	scnprintf(child->name, sizeof(child->name),
-		  (is_cardbus ? "PCI CardBus %04x:%02x" : "PCI Bus %04x:%02x"),
+	scnprintf(child->name, sizeof(child->name), "PCI Bus %04x:%02x",
 		  pci_domain_nr(bus), child->number);
 
 	pbus_validate_busn(child);

drivers/pci/setup-cardbus.c

@@ -3,14 +3,19 @@
  * Cardbus bridge setup routines.
  */
 
+#include <linux/bitfield.h>
 #include <linux/errno.h>
 #include <linux/ioport.h>
 #include <linux/pci.h>
 #include <linux/sizes.h>
+#include <linux/sprintf.h>
 #include <linux/types.h>
 
 #include "pci.h"
 
+#define CARDBUS_LATENCY_TIMER		176	/* secondary latency timer */
+#define CARDBUS_RESERVE_BUSNR		3
+
 #define DEFAULT_CARDBUS_IO_SIZE		SZ_256
 #define DEFAULT_CARDBUS_MEM_SIZE	SZ_64M
 /* pci=cbmemsize=nnM,cbiosize=nn can override this */
@@ -186,3 +191,116 @@ int pci_setup_cardbus(char *str)
 
 	return -ENOENT;
 }
+
+int pci_cardbus_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
+				   u32 buses, int max,
+				   unsigned int available_buses, int pass)
+{
+	struct pci_bus *child;
+	bool fixed_buses;
+	u8 fixed_sec, fixed_sub;
+	int next_busnr;
+	u32 i, j = 0;
+
+	/*
+	 * We need to assign a number to this bus which we always do in the
+	 * second pass.
+	 */
+	if (!pass) {
+		/*
+		 * Temporarily disable forwarding of the configuration
+		 * cycles on all bridges in this bus segment to avoid
+		 * possible conflicts in the second pass between two bridges
+		 * programmed with overlapping bus ranges.
+		 */
+		pci_write_config_dword(dev, PCI_PRIMARY_BUS,
+				       buses & PCI_SEC_LATENCY_TIMER_MASK);
+		return max;
+	}
+
+	/* Clear errors */
+	pci_write_config_word(dev, PCI_STATUS, 0xffff);
+
+	/* Read bus numbers from EA Capability (if present) */
+	fixed_buses = pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub);
+	if (fixed_buses)
+		next_busnr = fixed_sec;
+	else
+		next_busnr = max + 1;
+
+	/*
+	 * Prevent assigning a bus number that already exists. This can
+	 * happen when a bridge is hot-plugged, so in this case we only
+	 * re-scan this bus.
+	 */
+	child = pci_find_bus(pci_domain_nr(bus), next_busnr);
+	if (!child) {
+		child = pci_add_new_bus(bus, dev, next_busnr);
+		if (!child)
+			return max;
+		pci_bus_insert_busn_res(child, next_busnr, bus->busn_res.end);
+	}
+	max++;
+	if (available_buses)
+		available_buses--;
+
+	buses = (buses & PCI_SEC_LATENCY_TIMER_MASK) |
+		FIELD_PREP(PCI_PRIMARY_BUS_MASK, child->primary) |
+		FIELD_PREP(PCI_SECONDARY_BUS_MASK, child->busn_res.start) |
+		FIELD_PREP(PCI_SUBORDINATE_BUS_MASK, child->busn_res.end);
+
+	/*
+	 * yenta.c forces a secondary latency timer of 176.
+	 * Copy that behaviour here.
+	 */
+	buses &= ~PCI_SEC_LATENCY_TIMER_MASK;
+	buses |= FIELD_PREP(PCI_SEC_LATENCY_TIMER_MASK, CARDBUS_LATENCY_TIMER);
+
+	/* We need to blast all three values with a single write */
+	pci_write_config_dword(dev, PCI_PRIMARY_BUS, buses);
+
+	/*
+	 * For CardBus bridges, we leave 4 bus numbers as cards with a
+	 * PCI-to-PCI bridge can be inserted later.
+	 */
+	for (i = 0; i < CARDBUS_RESERVE_BUSNR; i++) {
+		struct pci_bus *parent = bus;
+
+		if (pci_find_bus(pci_domain_nr(bus), max + i + 1))
+			break;
+
+		while (parent->parent) {
+			if (!pcibios_assign_all_busses() &&
+			    (parent->busn_res.end > max) &&
+			    (parent->busn_res.end <= max + i)) {
+				j = 1;
+			}
+			parent = parent->parent;
+		}
+		if (j) {
+			/*
+			 * Often, there are two CardBus bridges -- try to
+			 * leave one valid bus number for each one.
+			 */
+			i /= 2;
+			break;
+		}
+	}
+	max += i;
+
+	/*
+	 * Set subordinate bus number to its real value. If fixed
+	 * subordinate bus number exists from EA capability then use it.
+	 */
+	if (fixed_buses)
+		max = fixed_sub;
+	pci_bus_update_busn_res_end(child, max);
+	pci_write_config_byte(dev, PCI_SUBORDINATE_BUS, max);
+
+	scnprintf(child->name, sizeof(child->name), "PCI CardBus %04x:%02x",
+		  pci_domain_nr(bus), child->number);
+
+	pbus_validate_busn(child);
+
+	return max;
+}