Re: [PATCH v9 3/7] PCI: Add parent_bus_offset to resource_entry
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2025-02-27 00:23:29
Also in:
imx, linux-devicetree, linux-pci, lkml
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. ...
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+++ 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);
I don't know exactly where it needs to go, but I think we can call .cpu_addr_fixup() once at startup on the base of the region. This will tell us the offset that applies to the entire region, i.e., parent_bus_offset. Then we can remove all the .cpu_addr_fixup() calls in cdns_pcie_host_init_address_translation(), cdns_pcie_set_outbound_region(), and dw_pcie_prog_outbound_atu(). Until we can get rid of all the .cpu_addr_fixup() implementations, We'll still have that single call at startup (I guess once for cadence and another for designware), but it should simplify the current callers quite a bit.
quoted hunk ↗ jump to hunk
} /* 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