[v9,3/7] PCI: Add parent_bus_offset to resource_entry

Commit Message

Frank Li Jan. 28, 2025, 10:07 p.m. UTC

Introduce `parent_bus_offset` in `resource_entry` and a new API,
`pci_add_resource_parent_bus_offset()`, to provide necessary information
for PCI controllers with address translation units.

Typical PCI data flow involves:
  CPU (CPU address) -> Bus Fabric (Intermediate address) ->
  PCI Controller (PCI bus address) -> PCI Bus.

While most bus fabrics preserve address consistency, some modify addresses
to intermediate values. The `parent_bus_offset` enables PCI controllers to
translate these intermediate addresses correctly to PCI bus addresses.

Pave the road to remove hardcoded cpu_addr_fixup() and similar patterns in
PCI controller drivers.

Signed-off-by: Frank Li <[e-mail]>
---
change from v9 to v10
- new patch
---
 drivers/pci/bus.c            | 11 +++++++++--
 drivers/pci/of.c             | 12 +++++++++++-
 include/linux/pci.h          |  2 ++
 include/linux/resource_ext.h |  1 +
 4 files changed, 23 insertions(+), 3 deletions(-)

Patch

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 98910bc0fcc4e..52e88c391e256 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -31,8 +31,8 @@  struct pci_bus_resource {
 	struct resource		*res;
 };
 
-void pci_add_resource_offset(struct list_head *resources, struct resource *res,
-			     resource_size_t offset)
+void pci_add_resource_parent_bus_offset(struct list_head *resources, struct resource *res,
+					resource_size_t offset, resource_size_t parent_bus_offset)
 {
 	struct resource_entry *entry;
 
@@ -43,8 +43,15 @@  void pci_add_resource_offset(struct list_head *resources, struct resource *res,
 	}
 
 	entry->offset = offset;
+	entry->parent_bus_offset = parent_bus_offset;
 	resource_list_add_tail(entry, resources);
 }
+
+void pci_add_resource_offset(struct list_head *resources, struct resource *res,
+			     resource_size_t offset)
+{
+	pci_add_resource_parent_bus_offset(resources, res, offset, 0);
+}
 EXPORT_SYMBOL(pci_add_resource_offset);
 
 void pci_add_resource(struct list_head *resources, struct resource *res)
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 7a806f5c0d201..aa4a2e266c55e 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -402,7 +402,17 @@  static int devm_of_pci_get_host_bridge_resources(struct device *dev,
 			res->flags &= ~IORESOURCE_MEM_64;
 		}
 
-		pci_add_resource_offset(resources, res,	res->start - range.pci_addr);
+		/*
+		 * IORESOURCE_IO res->start is io space start address.
+		 * IORESOURCE_MEM res->start is cpu start address, which is the
+		 * same as range.cpu_addr.
+		 *
+		 * Use (range.cpu_addr - range.parent_bus_addr) to align both
+		 * IO and MEM's parent_bus_offset always offset to cpu address.
+		 */
+
+		pci_add_resource_parent_bus_offset(resources, res, res->start - range.pci_addr,
+						   range.cpu_addr - range.parent_bus_addr);
 	}
 
 	/* Check for dma-ranges property */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 47b31ad724fa5..0d7e67b47be47 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1510,6 +1510,8 @@  static inline void pci_release_config_region(struct pci_dev *pdev,
 void pci_add_resource(struct list_head *resources, struct resource *res);
 void pci_add_resource_offset(struct list_head *resources, struct resource *res,
 			     resource_size_t offset);
+void pci_add_resource_parent_bus_offset(struct list_head *resources, struct resource *res,
+					resource_size_t offset, resource_size_t parent_bus_offset);
 void pci_free_resource_list(struct list_head *resources);
 void pci_bus_add_resource(struct pci_bus *bus, struct resource *res);
 struct resource *pci_bus_resource_n(const struct pci_bus *bus, int n);
diff --git a/include/linux/resource_ext.h b/include/linux/resource_ext.h
index ff0339df56afc..b6ec6cc318203 100644
--- a/include/linux/resource_ext.h
+++ b/include/linux/resource_ext.h
@@ -24,6 +24,7 @@  struct resource_entry {
 	struct list_head	node;
 	struct resource		*res;	/* In master (CPU) address space */
 	resource_size_t		offset;	/* Translation offset for bridge */
+	resource_size_t		parent_bus_offset; /* Parent bus address offset for bridge */
 	struct resource		__res;	/* Default storage for res */
 };