Subject: Re: [RFC/PATCH] of: Match PCI devices to OF nodes generically

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 04 Apr 2011 13:27:10 +1000

On Mon, 2011-04-04 at 12:04 +1000, Benjamin Herrenschmidt wrote:
> powerpc has two different ways of matching PCI devices to their
> corresponding OF node (if any) for historical reasons. The ppc64 one
> does a scan looking for matching bus/dev/fn, while the ppc32 one does a
> scan looking only for matching dev/fn on each level in order to be
> agnostic to busses being renumbered (which Linux does on some
> platforms).
> 
> This removes both and instead moves the matching code to the PCI core
> itself. It's the most logical place to do it: when a pci_dev is created,
> we know the parent and thus can do a single level scan for the matching
> device_node (if any).
> 
> The benefit is that all archs now get the matching for free. There's one
> hook the arch might want to provide to match a PHB bus to its device
> node. A default weak implementation is provided that looks for the
> parent device device node, but it's not entirely reliable on powerpc for
> various reasons so powerpc provides its own.
> 
> Dave, I don't think I broke anything in sparc land but I haven't tested
> (and have to admit haven't build-tested yet either).
> 
> Not-signed-off-yet. Tested on a few ppc's but not the whole range yet
> either, mostly posted for comments.

Nice, looks like I forgot to add the new drivers/pci/of.c file :-)
Here's a new patch. Also added linux-pci to the CC list.

diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index 5e156e0..a4c8e4a 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -169,18 +169,18 @@ static inline struct pci_controller *pci_bus_to_host(const struct pci_bus *bus)
 	return bus->sysdata;
 }
 
-#ifndef CONFIG_PPC64
+static inline struct device_node *pci_device_to_OF_node(struct pci_dev *dev)
+{
+	return dev->dev.of_node;
+}
 
 static inline struct device_node *pci_bus_to_OF_node(struct pci_bus *bus)
 {
-	struct pci_controller *host;
-
-	if (bus->self)
-		return pci_device_to_OF_node(bus->self);
-	host = pci_bus_to_host(bus);
-	return host ? host->dn : NULL;
+	return bus->dev.of_node;
 }
 
+#ifndef CONFIG_PPC64
+
 static inline int isa_vaddr_is_ioport(void __iomem *address)
 {
 	/* No specific ISA handling on ppc32 at this stage, it
@@ -223,17 +223,8 @@ struct pci_dn {
 /* Get the pointer to a device_node's pci_dn */
 #define PCI_DN(dn)	((struct pci_dn *) (dn)->data)
 
-extern struct device_node *fetch_dev_dn(struct pci_dev *dev);
 extern void * update_dn_pci_info(struct device_node *dn, void *data);
 
-/* Get a device_node from a pci_dev.  This code must be fast except
- * in the case where the sysdata is incorrect and needs to be fixed
- * up (this will only happen once). */
-static inline struct device_node *pci_device_to_OF_node(struct pci_dev *dev)
-{
-	return dev->dev.of_node ? dev->dev.of_node : fetch_dev_dn(dev);
-}
-
 static inline int pci_device_from_OF_node(struct device_node *np,
 					  u8 *bus, u8 *devfn)
 {
@@ -244,14 +235,6 @@ static inline int pci_device_from_OF_node(struct device_node *np,
 	return 0;
 }
 
-static inline struct device_node *pci_bus_to_OF_node(struct pci_bus *bus)
-{
-	if (bus->self)
-		return pci_device_to_OF_node(bus->self);
-	else
-		return bus->dev.of_node; /* Must be root bus (PHB) */
-}
-
 /** Find the bus corresponding to the indicated device node */
 extern struct pci_bus *pcibios_find_pci_bus(struct device_node *dn);
 
diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h
index 7d77909..1f52268 100644
--- a/arch/powerpc/include/asm/pci.h
+++ b/arch/powerpc/include/asm/pci.h
@@ -179,8 +179,7 @@ extern int remove_phb_dynamic(struct pci_controller *phb);
 extern struct pci_dev *of_create_pci_dev(struct device_node *node,
 					struct pci_bus *bus, int devfn);
 
-extern void of_scan_pci_bridge(struct device_node *node,
-				struct pci_dev *dev);
+extern void of_scan_pci_bridge(struct pci_dev *dev);
 
 extern void of_scan_bus(struct device_node *node, struct pci_bus *bus);
 extern void of_rescan_bus(struct device_node *node, struct pci_bus *bus);
diff --git a/arch/powerpc/include/asm/prom.h b/arch/powerpc/include/asm/prom.h
index c189aa5..2b888cc 100644
--- a/arch/powerpc/include/asm/prom.h
+++ b/arch/powerpc/include/asm/prom.h
@@ -32,7 +32,6 @@ struct pci_dev;
 extern int pci_device_from_OF_node(struct device_node *node,
 				   u8* bus, u8* devfn);
 extern struct device_node* pci_busdev_to_OF_node(struct pci_bus *, int);
-extern struct device_node* pci_device_to_OF_node(struct pci_dev *);
 extern void pci_create_OF_bus_map(void);
 #endif
 
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 893af2a..47c516b 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -1097,9 +1097,6 @@ void __devinit pcibios_setup_bus_devices(struct pci_bus *bus)
 		if (dev->is_added)
 			continue;
 
-		/* Setup OF node pointer in the device */
-		dev->dev.of_node = pci_device_to_OF_node(dev);
-
 		/* Fixup NUMA node as it may not be setup yet by the generic
 		 * code and is needed by the DMA init
 		 */
@@ -1685,6 +1682,13 @@ int early_find_capability(struct pci_controller *hose, int bus, int devfn,
 	return pci_bus_find_capability(fake_pci_bus(hose, bus), devfn, cap);
 }
 
+struct device_node * pcibios_get_phb_of_node(struct pci_bus *bus)
+{
+	struct pci_controller *hose = bus->sysdata;
+
+	return of_node_get(hose->dn);
+}
+
 /**
  * pci_scan_phb - Given a pci_controller, setup and scan the PCI bus
  * @hose: Pointer to the PCI host controller instance structure
@@ -1705,7 +1709,6 @@ void __devinit pcibios_scan_phb(struct pci_controller *hose)
 			hose->global_number);
 		return;
 	}
-	bus->dev.of_node = of_node_get(node);
 	bus->secondary = hose->first_busno;
 	hose->bus = bus;
 
diff --git a/arch/powerpc/kernel/pci_32.c b/arch/powerpc/kernel/pci_32.c
index bedb370..700a826 100644
--- a/arch/powerpc/kernel/pci_32.c
+++ b/arch/powerpc/kernel/pci_32.c
@@ -276,12 +276,6 @@ pci_busdev_to_OF_node(struct pci_bus *bus, int devfn)
 }
 EXPORT_SYMBOL(pci_busdev_to_OF_node);
 
-struct device_node*
-pci_device_to_OF_node(struct pci_dev *dev)
-{
-	return pci_busdev_to_OF_node(dev->bus, dev->devfn);
-}
-EXPORT_SYMBOL(pci_device_to_OF_node);
 
 static int
 find_OF_pci_device_filter(struct device_node* node, void* data)
diff --git a/arch/powerpc/kernel/pci_dn.c b/arch/powerpc/kernel/pci_dn.c
index d225d99..8cb66a2 100644
--- a/arch/powerpc/kernel/pci_dn.c
+++ b/arch/powerpc/kernel/pci_dn.c
@@ -143,53 +143,6 @@ void __devinit pci_devs_phb_init_dynamic(struct pci_controller *phb)
 	traverse_pci_devices(dn, update_dn_pci_info, phb);
 }
 
-/*
- * Traversal func that looks for a <busno,devfcn> value.
- * If found, the pci_dn is returned (thus terminating the traversal).
- */
-static void *is_devfn_node(struct device_node *dn, void *data)
-{
-	int busno = ((unsigned long)data >> 8) & 0xff;
-	int devfn = ((unsigned long)data) & 0xff;
-	struct pci_dn *pci = dn->data;
-
-	if (pci && (devfn == pci->devfn) && (busno == pci->busno))
-		return dn;
-	return NULL;
-}
-
-/*
- * This is the "slow" path for looking up a device_node from a
- * pci_dev.  It will hunt for the device under its parent's
- * phb and then update of_node pointer.
- *
- * It may also do fixups on the actual device since this happens
- * on the first read/write.
- *
- * Note that it also must deal with devices that don't exist.
- * In this case it may probe for real hardware ("just in case")
- * and add a device_node to the device tree if necessary.
- *
- * Is this function necessary anymore now that dev->dev.of_node is
- * used to store the node pointer?
- *
- */
-struct device_node *fetch_dev_dn(struct pci_dev *dev)
-{
-	struct pci_controller *phb = dev->sysdata;
-	struct device_node *dn;
-	unsigned long searchval = (dev->bus->number << 8) | dev->devfn;
-
-	if (WARN_ON(!phb))
-		return NULL;
-
-	dn = traverse_pci_devices(phb->dn, is_devfn_node, (void *)searchval);
-	if (dn)
-		dev->dev.of_node = dn;
-	return dn;
-}
-EXPORT_SYMBOL(fetch_dev_dn);
-
 /** 
  * pci_devs_phb_init - Initialize phbs and pci devs under them.
  * 
diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
index 1e89a72..fe0a5ad 100644
--- a/arch/powerpc/kernel/pci_of_scan.c
+++ b/arch/powerpc/kernel/pci_of_scan.c
@@ -202,9 +202,9 @@ EXPORT_SYMBOL(of_create_pci_dev);
  * this routine in turn call of_scan_bus() recusively to scan for more child
  * devices.
  */
-void __devinit of_scan_pci_bridge(struct device_node *node,
-				  struct pci_dev *dev)
+void __devinit of_scan_pci_bridge(struct pci_dev *dev)
 {
+	struct device_node *node = dev->dev.of_node;
 	struct pci_bus *bus;
 	const u32 *busrange, *ranges;
 	int len, i, mode;
@@ -238,7 +238,6 @@ void __devinit of_scan_pci_bridge(struct device_node *node,
 	bus->primary = dev->bus->number;
 	bus->subordinate = busrange[1];
 	bus->bridge_ctl = 0;
-	bus->dev.of_node = of_node_get(node);
 
 	/* parse ranges property */
 	/* PCI #address-cells == 3 and #size-cells == 2 always */
@@ -335,9 +334,7 @@ static void __devinit __of_scan_bus(struct device_node *node,
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
 		    dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
-			struct device_node *child = pci_device_to_OF_node(dev);
-			if (child)
-				of_scan_pci_bridge(child, dev);
+			of_scan_pci_bridge(dev);
 		}
 	}
 }
diff --git a/arch/sparc/kernel/pci.c b/arch/sparc/kernel/pci.c
index 713dc91..e539d23 100644
--- a/arch/sparc/kernel/pci.c
+++ b/arch/sparc/kernel/pci.c
@@ -284,7 +284,7 @@ static struct pci_dev *of_create_pci_dev(struct pci_pbm_info *pbm,
 	dev->sysdata = node;
 	dev->dev.parent = bus->bridge;
 	dev->dev.bus = &pci_bus_type;
-	dev->dev.of_node = node;
+	dev->dev.of_node = of_node_get(node);
 	dev->devfn = devfn;
 	dev->multifunction = 0;		/* maybe a lie? */
 	set_pcie_port_type(dev);
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 98d61c8..d5c3cb9 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -70,4 +70,6 @@ obj-$(CONFIG_PCI_STUB) += pci-stub.o
 
 obj-$(CONFIG_XEN_PCIDEV_FRONTEND) += xen-pcifront.o
 
+obj-$(CONFIG_OF) += of.o
+
 ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG
diff --git a/drivers/pci/hotplug/rpadlpar_core.c b/drivers/pci/hotplug/rpadlpar_core.c
index 0830347..1d002b1 100644
--- a/drivers/pci/hotplug/rpadlpar_core.c
+++ b/drivers/pci/hotplug/rpadlpar_core.c
@@ -158,7 +158,7 @@ static void dlpar_pci_add_bus(struct device_node *dn)
 	/* Scan below the new bridge */
 	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
 	    dev->hdr_type == PCI_HEADER_TYPE_CARDBUS)
-		of_scan_pci_bridge(dn, dev);
+		of_scan_pci_bridge(dev);
 
 	/* Map IO space for child bus, which may or may not succeed */
 	pcibios_map_io_space(dev->subordinate);
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
new file mode 100644
index 0000000..306d852
--- /dev/null
+++ b/drivers/pci/of.c
@@ -0,0 +1,87 @@
+/*
+ * PCI <-> OF mapping helpers
+ *
+ * Copyright 2011 IBM Corp.
+ * 
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include "pci.h"
+
+static int pci_check_one_of_node(struct pci_dev *dev, struct device_node *node)
+{
+	unsigned int size;
+	const __be32 *reg = of_get_property(node, "reg", &size);
+
+	if (reg && size >= 4 && ((reg[0] >> 8) & 0xff) == dev->devfn) {
+		dev->dev.of_node = of_node_get(node);
+		return 1;
+	}
+	return 0;
+}
+
+void pci_set_of_node(struct pci_dev *dev)
+{
+	struct device_node *parent, *node, *node2;
+
+	parent = dev->bus->dev.of_node;
+	if (!parent)
+		return;
+	for_each_child_of_node(parent, node) {
+		if (pci_check_one_of_node(dev, node))
+			return;
+		/*
+		 * Some OFs create a parent node "multifunc-device" as
+		 * a fake root for all functions of a multi-function
+		 * device we go down them as well.
+		 */
+                if (!strcmp(node->name, "multifunc-device")) {
+			for_each_child_of_node(node, node2) {
+				if (pci_check_one_of_node(dev, node2))
+					return;
+			}
+                }
+	}
+}
+
+void pci_release_of_node(struct pci_dev *dev)
+{
+	of_node_put(dev->dev.of_node);
+	dev->dev.of_node = NULL;
+}
+
+void pci_set_bus_of_node(struct pci_bus *bus)
+{
+	if (bus->self == NULL)
+		bus->dev.of_node = pcibios_get_phb_of_node(bus);
+	else
+		bus->dev.of_node = of_node_get(bus->self->dev.of_node);
+}
+
+void pci_release_bus_of_node(struct pci_bus *bus)
+{
+	of_node_put(bus->dev.of_node);
+	bus->dev.of_node = NULL;
+}
+
+struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
+{
+	/* This should only be called for PHBs */
+	if (WARN_ON(bus->self || bus->parent))
+		return NULL;
+
+	/* Look for a node pointer in either the intermediary device we
+	 * create above the root bus or it's own parent. Normally only
+	 * the later is populated.
+	 */
+	if (bus->bridge->of_node)
+		return of_node_get(bus->bridge->of_node);
+	if (bus->bridge->parent->of_node)
+		return of_node_get(bus->bridge->parent->of_node);
+	return NULL;
+}
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 44cbbba..347349b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -89,6 +89,7 @@ static void release_pcibus_dev(struct device *dev)
 	if (pci_bus->bridge)
 		put_device(pci_bus->bridge);
 	pci_bus_remove_resources(pci_bus);
+	pci_release_bus_of_node(pci_bus);
 	kfree(pci_bus);
 }
 
@@ -624,7 +625,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 
 	child->self = bridge;
 	child->bridge = get_device(&bridge->dev);
-
+	pci_set_bus_of_node(child);	
 	pci_set_bus_speed(child);
 
 	/* Set up default resource pointers and names.. */
@@ -1074,6 +1075,7 @@ static void pci_release_dev(struct device *dev)
 
 	pci_dev = to_pci_dev(dev);
 	pci_release_capabilities(pci_dev);
+	pci_release_of_node(pci_dev);
 	kfree(pci_dev);
 }
 
@@ -1150,6 +1152,7 @@ struct pci_dev *alloc_pci_dev(void)
 }
 EXPORT_SYMBOL(alloc_pci_dev);
 
+
 /*
  * Read the config data for a PCI device, sanity-check it
  * and fill in the dev structure...
@@ -1193,6 +1196,8 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
 	dev->vendor = l & 0xffff;
 	dev->device = (l >> 16) & 0xffff;
 
+	pci_set_of_node(dev);
+
 	if (pci_setup_device(dev)) {
 		kfree(dev);
 		return NULL;
@@ -1445,6 +1450,7 @@ struct pci_bus * pci_create_bus(struct device *parent,
 		goto dev_reg_err;
 	b->bridge = get_device(dev);
 	device_enable_async_suspend(b->bridge);
+	pci_set_bus_of_node(b);
 
 	if (!parent)
 		set_dev_node(b->bridge, pcibus_to_node(b));
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 96f70d7..e5111da 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1543,5 +1543,22 @@ int pci_vpd_find_tag(const u8 *buf, unsigned int off, unsigned int len, u8 rdt);
 int pci_vpd_find_info_keyword(const u8 *buf, unsigned int off,
 			      unsigned int len, const char *kw);
 
+/* PCI <-> OF binding helpers */
+#ifdef  CONFIG_OF
+#include <linux/of.h>
+extern void pci_set_of_node(struct pci_dev *dev);
+extern void pci_release_of_node(struct pci_dev *dev);
+extern void pci_set_bus_of_node(struct pci_bus *bus);
+extern void pci_release_bus_of_node(struct pci_bus *bus);
+
+/* Arch may override this (weak) */
+extern struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus);
+
+
+#else /* CONFIG_OF */
+static void pci_locate_of_node(struct pci_dev *dev) { }
+static void pci_release_of_node(struct pci_dev *dev) { }
+#endif  /* CONFIG_OF */
+
 #endif /* __KERNEL__ */
 #endif /* LINUX_PCI_H */