[pci] Add minimal PCI bridge driver

Add a minimal driver for PCI bridges that can be used to locate the
bridge to which a PCI device is attached.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/bus/pcibridge.c

@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2022 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stddef.h>
+#include <stdint.h>
+#include <errno.h>
+#include <byteswap.h>
+#include <ipxe/pci.h>
+#include <ipxe/pcibridge.h>
+
+/** @file
+ *
+ * PCI-to-PCI bridge
+ *
+ */
+
+/** List of all PCI bridges */
+static LIST_HEAD ( pcibridges );
+
+/**
+ * Find bridge attached to a PCI device
+ *
+ * @v pci		PCI device
+ * @ret bridge		PCI bridge, or NULL
+ */
+struct pci_bridge * pcibridge_find ( struct pci_device *pci ) {
+	unsigned int bus = PCI_BUS ( pci->busdevfn );
+	struct pci_bridge *bridge;
+
+	/* Find matching bridge */
+	list_for_each_entry ( bridge, &pcibridges, list ) {
+		if ( bus == bridge->secondary )
+			return bridge;
+	}
+
+	return NULL;
+}
+
+/**
+ * Probe PCI device
+ *
+ * @v pci		PCI device
+ * @ret rc		Return status code
+ */
+static int pcibridge_probe ( struct pci_device *pci ) {
+	struct pci_bridge *bridge;
+	uint16_t base;
+	uint16_t limit;
+	int rc;
+
+	/* Allocate and initialise structure */
+	bridge = zalloc ( sizeof ( *bridge ) );
+	if ( ! bridge ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	bridge->pci = pci;
+
+	/* Read configuration */
+	pci_read_config_dword ( pci, PCI_PRIMARY, &bridge->buses );
+	cpu_to_le32s ( &buses );
+	pci_read_config_word ( pci, PCI_MEM_BASE, &base );
+	bridge->membase = ( ( base & ~PCI_MEM_MASK ) << 16 );
+	pci_read_config_word ( pci, PCI_MEM_LIMIT, &limit );
+	bridge->memlimit = ( ( ( ( limit | PCI_MEM_MASK ) + 1 ) << 16 ) - 1 );
+	DBGC ( bridge, "BRIDGE " PCI_FMT " bus %02x to [%02x,%02x) mem "
+	       "[%08x,%08x)\n", PCI_ARGS ( pci ), bridge->primary,
+	       bridge->secondary, bridge->subordinate, bridge->membase,
+	       bridge->memlimit );
+
+	/* Add to list of PCI bridges */
+	list_add ( &bridge->list, &pcibridges );
+
+	pci_set_drvdata ( pci, bridge );
+	return 0;
+
+	free ( bridge );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Remove PCI device
+ *
+ * @v pci		PCI device
+ */
+static void pcibridge_remove ( struct pci_device *pci ) {
+	struct pci_bridge *bridge = pci_get_drvdata ( pci );
+
+	/* Remove from list of bridges */
+	list_del ( &bridge->list );
+
+	/* Free device */
+	free ( bridge );
+}
+
+/** Bridge PCI device IDs */
+static struct pci_device_id pcibridge_ids[] = {
+	PCI_ROM ( 0xffff, 0xffff, "bridge", "Bridge", 0 ),
+};
+
+/** Bridge PCI driver */
+struct pci_driver pcibridge_driver __pci_driver = {
+	.ids = pcibridge_ids,
+	.id_count = ( sizeof ( pcibridge_ids ) / sizeof ( pcibridge_ids[0] ) ),
+	.class = PCI_CLASS_ID ( PCI_CLASS_BRIDGE, PCI_CLASS_BRIDGE_PCI,
+				PCI_ANY_ID ),
+	.probe = pcibridge_probe,
+	.remove = pcibridge_remove,
+};

src/include/ipxe/errfile.h

@@ -217,6 +217,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_rdc		     ( ERRFILE_DRIVER | 0x00d10000 )
 #define ERRFILE_ice		     ( ERRFILE_DRIVER | 0x00d20000 )
 #define ERRFILE_ecam		     ( ERRFILE_DRIVER | 0x00d30000 )
+#define ERRFILE_pcibridge	     ( ERRFILE_DRIVER | 0x00d40000 )
 
 #define ERRFILE_aoe			( ERRFILE_NET | 0x00000000 )
 #define ERRFILE_arp			( ERRFILE_NET | 0x00010000 )

src/include/ipxe/pci.h

@@ -127,6 +127,10 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 /** Network controller */
 #define PCI_CLASS_NETWORK	0x02
 
+/** Bridge device */
+#define PCI_CLASS_BRIDGE	0x06
+#define PCI_CLASS_BRIDGE_PCI		0x04	/**< PCI-to-PCI bridge */
+
 /** Serial bus controller */
 #define PCI_CLASS_SERIAL	0x0c
 #define PCI_CLASS_SERIAL_USB		0x03	/**< USB controller */
@@ -135,9 +139,20 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define PCI_CLASS_SERIAL_USB_EHCI	 0x20	/**< ECHI USB controller */
 #define PCI_CLASS_SERIAL_USB_XHCI	 0x30	/**< xHCI USB controller */
 
+/** Primary bus number */
+#define PCI_PRIMARY		0x18
+
+/** Secondary bus number */
+#define PCI_SECONDARY		0x19
+
 /** Subordinate bus number */
 #define PCI_SUBORDINATE		0x1a
 
+/** Memory base and limit */
+#define PCI_MEM_BASE		0x20
+#define PCI_MEM_LIMIT		0x22
+#define PCI_MEM_MASK			0x000f
+
 /** Construct PCI class
  *
  * @v base		Base class (or PCI_ANY_ID)

src/include/ipxe/pcibridge.h

@@ -0,0 +1,43 @@
+#ifndef _IPXE_PCIBRIDGE_H
+#define _IPXE_PCIBRIDGE_H
+
+/** @file
+ *
+ * PCI-to-PCI bridge
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/list.h>
+#include <ipxe/pci.h>
+
+/** A PCI-to-PCI bridge */
+struct pci_bridge {
+	/** PCI device */
+	struct pci_device *pci;
+	/** Bridge numbers */
+	union {
+		/** Raw dword */
+		uint32_t buses;
+		struct {
+			/** Primary bus */
+			uint8_t primary;
+			/** Secondary bus */
+			uint8_t secondary;
+			/** Subordinate bus */
+			uint8_t subordinate;
+		} __attribute__ (( packed ));
+	};
+	/** Memory base */
+	uint32_t membase;
+	/** Memory limit */
+	uint32_t memlimit;
+	/** List of bridges */
+	struct list_head list;
+};
+
+extern struct pci_bridge * pcibridge_find ( struct pci_device *pci );
+
+#endif /* _IPXE_PCIBRIDGE_H */