> ## Documentation Index
> Fetch the complete documentation index at: https://dragonwingdocs-staging.qualcomm.com/llms.txt
> Use this file to discover all available pages before exploring further.
# PCIe
PCIe(Peripheral Component Interconnect Express)使用双向连接同时发送和接收信息。设备之间的路径称为**链路(Link)**,由一个或多个称为\*\*通道(Lane)\*\*的发送/接收对组成。
## 硬件规格
### IQ-8275 PCIe 控制器
| 参数 | PCIe RC1 | PCIe RC0 |
| ---------- | ------------------------------------------------------------------------ | ------------------------------------------------------------------------ |
| **速率** | Gen4 2 通道(8 GT/s) | Gen4 4 通道(8 GT/s) |
| **配置空间** | 0x40100000(1 MB) | 0x60100000(1 MB) |
| **I/O 空间** | 0x40200000(1 MB) | 0x60200000(1 MB) |
| **BAR 空间** | 0x40300000(509 MB) | 0x60300000(509 MB) |
| **电源轨** | vreg\_l5a (VDD\_A\_PCIE\_0\_CORE), vreg\_l1c (VDD\_A\_PCIE\_0\_PLL\_1P2) | vreg\_l5a (VDD\_A\_PCIE\_1\_CORE), vreg\_l1c (VDD\_A\_PCIE\_1\_PLL\_1P2) |
| **中断** | MSI 和 PCI legacy | MSI 和 PCI legacy |
| **电源管理** | ASPM (L1/L1ss, L0s) | ASPM (L1/L1ss, L0s) |
### EVK 硬件配置
* **PCIe0**:Gen4 2 通道 — M.2 E key(Wi-Fi)或扩展(可通过 SW1-1 开关选择)
* **PCIe1**:Gen4 4 通道 — PCIe x4 插槽或扩展(可通过 SW1-2 开关选择)
## 架构
| 层 | 关键特性 |
| --------- | ------------------------------ |
| **物理层** | 链路训练、8b/10b 编码、串行转换 |
| **数据链路层** | DLLP 组装、LCRC 生成、ACK/NAK 重放 |
| **事务层** | TLP 组装、ECRC、流量控制、QoS(TC→VC 映射) |
### PCIe 连接类型
| 类型 | 说明 |
| --------------------- | ----------------- |
| **Root Complex (RC)** | 将 CPU 连接到 PCIe 拓扑 |
| **Switch** | 在超过 2 个端口之间路由数据包 |
| **Bridge** | 连接不同的总线 |
| **Endpoint (EP)** | 仅有上行端口的叶子设备 |
## 软件驱动配置
### 内核配置
```
CONFIG_HOTPLUG_PCI=y
CONFIG_PCI_HOST_GENERIC=y
CONFIG_PCIE_DW_PLAT_HOST=y
CONFIG_PCIE_QCOM=y
CONFIG_PCI_ENDPOINT=y
CONFIG_PCIEASPM=y
CONFIG_PCIEASPM_POWER_SUPERSAVE=y
CONFIG_BLK_DEV_NVME=y
CONFIG_NVME_CORE=y
```
### 设备树源文件
| 平台 | 文件 |
| ------------------ | --------------------------------------- |
| Dragonwing IQ-8275 | `arch/arm64/boot/dts/qcom/sa8295p.dtsi` |
### 关键驱动文件
| 组件 | 路径 |
| ------------- | --------------------------------------------------- |
| PCIe 驱动 | `drivers/pci/controller/dwc/pcie-qcom.c` |
| DesignWare 主机 | `drivers/pci/controller/dwc/pcie-designware-host.c` |
| PHY 驱动 | `drivers/phy/qualcomm/phy-qcom-qmp-pcie.c` |
## 验证
```bash theme={null}
lspci
lspci -vv | grep -i "lnk"
cat /sys/bus/pci/devices/*/current_link_speed
cat /sys/bus/pci/devices/*/current_link_width
```
### NVMe over PCIe
```bash theme={null}
lspci | grep -i nvme
ls /dev/nvme*
nvme list
```
## 调试
```bash theme={null}
sudo su
echo 8 > /proc/sys/kernel/printk
echo "file pcie-qcom.c +p" > /sys/kernel/debug/dynamic_debug/control
dmesg | grep -i pcie
```
## 故障排除
```bash theme={null}
dmesg | grep -i phy | grep -i pcie
cat /sys/kernel/debug/regulator/regulator_summary | grep -i pcie
```
* 检查 PHY 电源轨和时钟配置
* 验证设备树设置
```bash theme={null}
lspci -tv
dmesg | grep -i pcie
```
* 验证 DIP 开关位置(SW1-1、SW1-2)
* 检查端点设备的电源供应
```bash theme={null}
lspci -vv | grep -i "lnk"
```
* 验证链路是否运行在预期的 Gen4 速率
* 如果 ASPM 设置过于激进,请进行调整
## 快速参考
```bash theme={null}
lspci # List all PCIe devices
lspci -vv # Detailed device info
lspci -tv # Tree view
dmesg | grep -i pcie # Kernel messages
cat /sys/bus/pci/devices/*/current_link_speed # Link speeds
```
## 资源
* [内核 PCIe 文档](https://www.kernel.org/doc/html/latest/PCI/index.html)
* [PCIe 规范](https://pcisig.com/specifications/pciexpress/technical_library/pciexpress_whitepaper.pdf)
* [Qualcomm PCIe 驱动](https://github.com/torvalds/linux/blob/master/drivers/pci/controller/dwc/pcie-qcom.c)