Question

PCI桥支持32/64 pref / no pref：

pci_bus 0000:00: root bus resource [bus 00-ff]
pci_bus 0000:00: root bus resource [io  0x0000-0xffff] 
pci_bus 0000:00: root bus resource [mem 0x1000000000-0x10ffffffff] (bus address [0x00000000-0xffffffff])
pci_bus 0000:00: root bus resource [mem 0x1100000000-0x11ffffffff pref] (bus address [0x00000000-0xffffffff])
pci_bus 0000:00: root bus resource [mem 0x2000000000-0x2fffffffff] (bus address [0x00000000-0xfffffffff])
pci_bus 0000:00: root bus resource [mem 0x3000000000-0x3fffffffff pref] (bus  address [0x00000000-0xfffffffff])

用2个BAR扫描端点：

pci 0000:01:00.0: BAR 2: assigned [mem 0x2100000000-0x211fffffff 64bit pref]
pci 0000:01:00.0: BAR 0: assigned [mem 0x1000000000-0x100007ffff]

桥显示窗口：

pci 0000:00:00.0: PCI bridge to [bus 01]
pci 0000:00:00.0:   bridge window [mem 0x1000000000-0x10000fffff]
pci 0000:00:00.0:   bridge window [mem 0x2100000000-0x211fffffff 64bit pref]

端点总结了BAR：

endpoint: BAR 0 addr = 0x1000000000, size = 524287
endpoint: BAR 1 addr = 0x2100000000, size = 536870911

BAR1的高32位被编程为什么？我期望0x21，但找到0x1。

这是因为pcibios_bus_to_resource / pcibios_resource_to_bus。它识别3个窗口偏移：

window->res->start = 1000000000 window->offset = 1000000000 window->res->end = 10FFFFFFFF
window->res->start = 1100000000 window->offset = 1100000000 window->res->end = 11FFFFFFFF
window->res->start = 2000000000 window->offset = 2000000000 window->res->end = 2FFFFFFFFF

在显示上述地址时添加偏移量，但在编程BAR时减去它们在端点中注册。所以0x2100000000变成0x100000000。

64位地址和32位BAR可能有意义，但为什么64位BAR会这样正确？

Answer 1

据此（摘自问题）：

    pci_bus 0000:00: root bus resource [mem 0x1000000000-0x10ffffffff] (bus address [0x00000000-0xffffffff])
    pci_bus 0000:00: root bus resource [mem 0x1100000000-0x11ffffffff pref] (bus address [0x00000000-0xffffffff])
    pci_bus 0000:00: root bus resource [mem 0x2000000000-0x2fffffffff] (bus address [0x00000000-0xfffffffff])
    pci_bus 0000:00: root bus resource [mem 0x3000000000-0x3fffffffff pref] (bus  address [0x00000000-0xfffffffff])

存储器地址0x20＆00; 0000＆00; 0000对应于总线地址0。

因此，如果要使用存储器地址0x21＆00; 0000＆00; 0000来访问设备中的BAR，则需要将其编程为0x1＆00; 0000＆00; 0000。

类似地，存储器地址0x10＆00; 0000＆00; 0000对应于总线地址0.因此，设备中的BAR被编程为0以使用存储器地址0x10＆00; 0000＆00; 0000来访问。

Linux 64位BAR编程

1 个答案: