7 Any config read will end up at pci_read_config(). This uses
8 uclass_get_device_by_seq() to get the PCI bus for a particular bus number.
9 Bus number 0 will need to be requested first, and the alias in the device
10 tree file will point to the correct device:
18 compatible = "sandbox,pci";
23 If there is no alias the devices will be numbered sequentially in the device
26 The call to uclass_get_device() will cause the PCI bus to be probed.
27 This does a scan of the bus to locate available devices. These devices are
28 bound to their appropriate driver if available. If there is no driver, then
29 they are bound to a generic PCI driver which does nothing.
31 After probing a bus, the available devices will appear in the device tree
34 Note that this is all done on a lazy basis, as needed, so until something is
35 touched on PCI (eg: a call to pci_find_devices()) it will not be probed.
37 PCI devices can appear in the flattened device tree. If they do, their node
38 often contains extra information which cannot be derived from the PCI IDs or
39 PCI class of the device. Each PCI device node must have a <reg> property, as
40 defined by the IEEE Std 1275-1994 PCI bus binding document v2.1. Compatible
41 string list is optional and generally not needed, since PCI is discoverable
42 bus, albeit there are justified exceptions. If the compatible string is
43 present, matching on it takes precedence over PCI IDs and PCI classes.
45 Note we must describe PCI devices with the same bus hierarchy as the
46 hardware, otherwise driver model cannot detect the correct parent/children
47 relationship during PCI bus enumeration thus PCI devices won't be bound to
48 their drivers accordingly. A working example like below:
53 compatible = "pci-x86";
55 ranges = <0x02000000 0x0 0x40000000 0x40000000 0 0x80000000
56 0x42000000 0x0 0xc0000000 0xc0000000 0 0x20000000
57 0x01000000 0x0 0x2000 0x2000 0 0xe000>;
62 compatible = "pci-bridge";
64 reg = <0x0000b800 0x0 0x0 0x0 0x0>;
69 compatible = "pci-bridge";
71 reg = <0x00010000 0x0 0x0 0x0 0x0>;
74 compatible = "pci8086,8811.00",
80 reg = <0x00025100 0x0 0x0 0x0 0x0
81 0x01025110 0x0 0x0 0x0 0x0>;
92 In this example, the root PCI bus node is the "/pci" which matches "pci-x86"
93 driver. It has a subnode "pcie@17,0" with driver "pci-bridge". "pcie@17,0"
94 also has subnode "topcliff@0,0" which is a "pci-bridge" too. Under that bridge,
95 a PCI UART device "uart@a,1" is described. This exactly reflects the hardware
96 bus hierarchy: on the root PCI bus, there is a PCIe root port which connects
97 to a downstream device Topcliff chipset. Inside Topcliff chipset, it has a
98 PCIe-to-PCI bridge and all the chipset integrated devices like the PCI UART
99 device are on the PCI bus. Like other devices in the device tree, if we want
100 to bind PCI devices before relocation, "u-boot,dm-pre-reloc" must be declared
101 in each of these nodes.
103 If PCI devices are not listed in the device tree, U_BOOT_PCI_DEVICE can be used
104 to specify the driver to use for the device. The device tree takes precedence
105 over U_BOOT_PCI_DEVICE. Plese note with U_BOOT_PCI_DEVICE, only drivers with
106 DM_FLAG_PRE_RELOC will be bound before relocation. If neither device tree nor
107 U_BOOT_PCI_DEVICE is provided, the built-in driver (either pci_bridge_drv or
108 pci_generic_drv) will be used.
114 With sandbox we need a device emulator for each device on the bus since there
115 is no real PCI bus. This works by looking in the device tree node for a
120 compatible = "pci-generic";
121 reg = <0xf800 0 0 0 0>;
123 compatible = "sandbox,swap-case";
127 This means that there is a 'sandbox,swap-case' driver at that bus position.
128 Note that the first cell in the 'reg' value is the bus/device/function. See
129 PCI_BDF() for the encoding (it is also specified in the IEEE Std 1275-1994
130 PCI bus binding document, v2.1)
132 When this bus is scanned we will end up with something like this:
134 `- * pci-controller @ 05c660c8, 0
135 `- pci@1f,0 @ 05c661c8, 63488
136 `- emul@1f,0 @ 05c662c8
138 When accesses go to the pci@1f,0 device they are forwarded to its child, the
141 The sandbox PCI drivers also support dynamic driver binding, allowing device
142 driver to declare the driver binding information via U_BOOT_PCI_DEVICE(),
143 eliminating the need to provide any device tree node under the host controller
144 node. It is required a "sandbox,dev-info" property must be provided in the
145 host controller node for this functionality to work.
147 pci1: pci-controller1 {
148 compatible = "sandbox,pci";
150 sandbox,dev-info = <0x08 0x00 0x1234 0x5678
151 0x0c 0x00 0x1234 0x5678>;
154 The "sandbox,dev-info" property specifies all dynamic PCI devices on this bus.
155 Each dynamic PCI device is encoded as 4 cells a group. The first and second
156 cells are PCI device number and function number respectively. The third and
157 fourth cells are PCI vendor ID and device ID respectively.
159 When this bus is scanned we will end up with something like this:
161 pci [ + ] pci_sandbo |-- pci-controller1
162 pci_emul [ ] sandbox_sw | |-- sandbox_swap_case_emul
163 pci_emul [ ] sandbox_sw | `-- sandbox_swap_case_emul
165 Note the difference from the statically declared device nodes is that the
166 device is directly attached to the host controller, instead of via a container
167 device like pci@1f,0.