RT-Thread RTOS
An open source embedded real-time operating system
PCI host controllers

Host controllers (<tt>ecam.c</tt>, <tt>host/</tt>)

SoC root complex drivers: map config space, parse DT **ranges**, call **rt_pci_host_bridge_probe**. Distinct from the PCI bridge function driver (PCI bridge function driver).

ECAM (<tt>ecam.c</tt>, <tt>ecam.h</tt>)

API Role
**pci_ecam_create(host_bridge, ops)** Attach **pci_generic_ecam_ops** (or variant) to host
**pci_ecam_map(bus, devfn, where)** Config MMIO address
**pci_generic_ecam_ops** Standard **bus_shift** ECAM

**struct pci_ecam_config_window**: **win** base, **bus_range[2]**, **bus_shift**, **ops**.

DesignWare / slot-0 quirk

**pci_dw_ecam_bus_ops**: on root bus, **devfn slot > 0** returns **NULL** from **map** (only device 0 on bus 0) — used by **snps,dw-pcie-ecam**, Marvell, Socionext compatibles.

Generic platform host (<tt>host/pci-host-generic.c</tt>)

**RT_PLATFORM_DRIVER_EXPORT(gen_pci_driver)**

compatible ECAM ops
**pci-host-ecam-generic** **pci_generic_ecam_ops**
**pci-host-cam-generic** CAM layout, **bus_shift = 16**
**snps,dw-pcie-ecam**, **marvell,armada8k-pcie-ecam**, … **pci_dw_ecam_bus_ops**

**pci_host_common_probe** (host/pci-host-common.c):

  1. **rt_pci_host_bridge_alloc**
  2. **rt_dm_dev_iomap(dev, 0)** — ECAM **reg**
  3. **rt_pci_host_bridge_init** — OFW ranges
  4. **pci_ecam_create**, **conf_win->win = base**
  5. **rt_pci_host_bridge_probe**

DesignWare host (<tt>host/dw/</tt>)

File Role
**pcie-dw_host.c** RC mode: DBI, link, **rt_pci_host_bridge_probe**
**pcie-dw_ep.c** EP mode — PCI endpoint (EP) mode
**pcie-dw_platfrom.c** Platform glue

Enable via **pci/host/dw/Kconfig**. DT binding typically **snps,dw-pcie** plus ECAM child node.

Host bridge callbacks (IRQ without full OFW)

**struct rt_pci_host_bridge** optional:

Field Role
**irq_slot(pdev, &pin)** ACPI/legacy slot for INTx
**irq_map(pdev, slot, pin)** Return Linux IRQ number

If NULL, OFW path or no INTx (PCI INTx interrupts, PCI and device tree).

Pitfalls

Issue Mitigation
ECAM **reg not iomapped** **pci_host_common_probe** fails with **-RT_EIO**
Empty **ranges** **rt_pci_ofw_parse_ranges** fails — no MEM/IO for BARs
Wrong **compatible** Pick ops matching hardware CAM vs ECAM
Confusing with **host-bridge.c** That file is PCI function driver for bridge devices

See also