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

Frank Li
2025-02-06T17:11:28Z

On Tue, Jan 28, 2025 at 05:07:36PM -0500, Frank Li wrote:
> 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 <Frank.Li@nxp.com>
> ---

Bjorn:

How do you think this method to handle parent_bus_offset? so other
pci host rc driver should be easy to use it.

Frank

> 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(-)
>
> 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 */
> };
>
>
> --
> 2.34.1
>