RT-Thread RTOS
An open source embedded real-time operating system
PCI / PCIe

PCI and PCIe overview

PCI/PCIe support in RT-Thread covers config-space access, bus enumeration, BAR assignment, INTx/MSI/MSI-X, and function drivers. Implementation layout matches **components/drivers/pci/**.

Source / topic Documentation
**probe.c** — scan, setup, drivers PCI enumeration and drivers
**access.c** — config accessors PCI config space access
**ecam.c**, **host/** — root complex PCI host controllers
**irq.c** — INTx assign/mask PCI INTx interrupts
**pme.c** — power management PCI power management
**ofw.c** — DT ranges/IRQ PCI and device tree
**msi/** PCI MSI and MSI-X
**host-bridge.c** — bridge function driver PCI bridge function driver
**endpoint/** — EP mode PCI endpoint (EP) mode

Header: **drivers/pci.h**. Requires **RT_USING_DM** and **RT_USING_PIC**.

Kconfig

Option Role
**RT_USING_PCI** Core PCI stack
**RT_PCI_MSI** MSI / MSI-X (default y)
**RT_PCI_ENDPOINT** Endpoint framework
**RT_PCI_ECAM** ECAM config access
**RT_PCI_SYS_64BIT** 64-bit resource alloc
**RT_PCI_CACHE_LINE_SIZE** Cache line bytes written to config
**RT_PCI_LOCKLESS** Skip global config spinlock

Host-specific options: **pci/host/Kconfig**, **pci/host/dw/Kconfig**.

Topology

CPU + Host Bridge (platform driver)
→ rt_pci_host_bridge
→ root_bus (bus 0)
→ scan: endpoints + PCI bridges
→ sub-buses
→ rt_pci_driver probe per function
Object Role
**struct rt_pci_host_bridge** Domain, **bus_regions**, **rt_pci_ops**, optional OFW node
**struct rt_pci_bus** Bus number, device list, **ops** chain
**struct rt_pci_device** BDF, BARs **resource[]**, caps, **irq**, bound driver
**struct rt_pci_driver** **ids[]**, **probe/remove**

BDF macros: **RT_PCI_DEVFN**, **RT_PCI_DEVID**, **RT_PCI_SLOT**, **RT_PCI_FUNC**.

Bring-up order

Full call chain (host → scan → BAR → function driver): PCI enumeration and drivers §「Full initialization flow」.

  1. Platform host driver probes — PCI host controllers
  2. **rt_pci_host_bridge_init** — **ranges**, **bus-range** — PCI and device tree
  3. **rt_pci_host_bridge_probe** — DFS enumeration, **rt_pci_setup_device**, **rt_pci_device_register**
  4. Bus **pci_probe** → **rt_pci_assign_irq** → function **pdrv->probe** — IRQ: PCI INTx interrupts, MSI: PCI MSI and MSI-X

Function driver checklist

  1. Wait until **rt_pci_setup_device** completed (BARs in **pdev->resource**).
  2. **void *base = rt_pci_iomap(pdev, bar)** before MMIO.
  3. **rt_pci_set_master** only when DMA is ready.
  4. IRQ: **rt_pci_alloc_vector** or **rt_pci_msi_enable** — not raw INTx unless legacy.
  5. **remove**: **rt_pci_free_vector**, **rt_pci_clear_master**, disable INTx.

When to use PCI

PCI Platform / AMBA
Device behind root complex with config space Fixed SoC block with only **reg/interrupts**

See also