Linux Kernel 如何管理 PCIe 设备

File	blank	comment	code	explanation
pci.c	950	1955	3667	capability list 的封装
probe.c	543	631	2137
setup-bus.c	333	373	1536
pci-sysfs.c	244	150	1170
pci-driver.c	283	331	1045
msi.c	258	276	1045
pci-acpi.c	205	175	989
pcie/aer.c	214	229	961
pcie/aspm.c	191	245	941
iov.c	189	177	725
p2pdma.c	164	240	601
pci.h	97	64	532
vpd.c	101	85	467
pcie/aer_inject.c	67	18	460
slot.c	0	0	379
access.c				访问配置空间的函数封装
ecam.c				ecam 的支持

其实，内核中处理 PCIe 的代码并不多。

关键结构体

• pci_dev : 将配置空间的信息会保存一些到里面
• pci_bus : 有点像是在描述 pci bridge 啊，从 pci_scan_bridge_extend 看，虽然 bridge 会形成一个 pci bus，但是这个 bus 的属性是通过 pci_bus 描述的
• pci_driver : 包含一个 device_driver
• pci_host_bridge
• pci_slot

scan 的过程

• pci_scan_child_bus
  • pci_scan_child_bus_extend
    • pci_scan_bridge_extend : If it’s a bridge, configure it and scan the bus behind it.
    • pci_scan_slot
    • pci_scan_single_device - pci_get_slot - pci_scan_device
      • pci_alloc_dev : 分配一个 struct pci_dev
      • pci_setup_device : pci_setup_device - Fill in class and map information of a device

probe 的过程

使用 e1000 的为例:

static struct pci_driver e1000_driver = {
	.name     = e1000_driver_name,
	.id_table = e1000_pci_tbl,
	.probe    = e1000_probe,
	.remove   = e1000_remove,
	.driver = {
		.pm = &e1000_pm_ops,
	},
	.shutdown = e1000_shutdown,
	.err_handler = &e1000_err_handler
};

• ret_from_fork
  • kernel_init
    • kernel_init_freeable
      • do_basic_setup
        • do_initcalls
          • do_initcall_level
            • do_one_initcall
              • driver_register
                • bus_add_driver
                  • driver_attach
                    • bus_for_each_dev
                      • __driver_attach
                        • __driver_attach
                          • driver_probe_device
                            • __driver_probe_device
                              • really_probe
                                • really_probe
                                  • call_driver_probe
                                    • pci_device_probe
                                      • __pci_device_probe
                                        • pci_call_probe
                                          • local_pci_probe
                                            • e1000_probe
• PCI drivers “discover” PCI devices in a system via pci_register_driver(). ¹
• pci_bus::probe和 pci_driver::probe 的关系
• pci_driver::probe 中完成的工作

Once the driver knows about a PCI device and takes ownership, the driver generally needs to perform the following initialization: ¹

• Enable the device
• Request MMIO/IOP resources
• Set the DMA mask size (for both coherent and streaming DMA)
• Allocate and initialize shared control data (pci_allocate_coherent())
• Access device configuration space (if needed)
• Register IRQ handler (request_irq())
• Initialize non-PCI (i.e. LAN/SCSI/etc parts of the chip)
• Enable DMA/processing engines

两个小教程可以玩玩

• drivers/pci/pci-stub.c
• drivers/pci/pci-pf-stub.c

You will also learn a bit about how PCI handles some nifty kernel features such as probing and power management.

For an in-depth discussion of PCI, such as device driver design, PCI bus features, and implementation details, refer to Linux Device Drivers and Understanding the Linux Kernel, as well as PCI specifications.

什么，Understanding the Linux Kernel 中间 讲过 pci

pci_device_id Device identifier. This is not a local ID used by Linux, but an ID defined accordingly to the PCI standard.

pci_dev Each PCI device is assigned a pci_dev instance, just as network devices are assigned net_device instances. This is the structure used by the kernel to refer to a PCI device.

pci_driver Defines the interface between the PCI layer and the device drivers. This structure consists mostly of function pointers. All PCI devices use it.

PCI devices are uniquely identified by a combination of parameters, including vendor, model, etc.

Each device driver registers with the kernel a vector of pci_device_id instances that lists the IDs of the devices it can handle.

PCI device drivers register and unregister with the kernel with pci_register_driver and pci_unregister_driver, respectively.

One of the great advantages of PCI is its elegant support for probing to find the IRQ and other resources each device needs.

The Big Picture 的这一节可以细品

想法: pci 是基础架构，pci 的三层 (事务，路由，物理)内核并不会参与， 但是，哪一个设备 和 对应的驱动关联 (nvme) 资源的分配 需要 pci driver 处理，一旦这些搞定之后，pci driver 就可以退居幕后了

PCIe 配置空间中是存在

https://stackoverflow.com/questions/72993292/how-to-get-irq-pins-in-pci

看看 kernel 中的

static const struct pci_device_id

本来以为 reset 是 pcie 的接口，但是发现 virtio 设备都没有这个

➜  ~ find /sys -name reset
/sys/devices/pci0000:00/0000:00:0c.0/reset
/sys/devices/pci0000:00/0000:00:0b.0/reset
/sys/devices/pci0000:00/0000:00:0a.0/reset
/sys/devices/virtual/block/zram0/reset
/sys/module/i915/parameters/reset

本站所有文章转发 CSDN 将按侵权追究法律责任，其它情况随意。

1. https://www.kernel.org/doc/html/latest/PCI/index.html ↩ ↩²