Any config read will end up at pci_read_config(). This uses
uclass_get_device_by_seq() to get the PCI bus for a particular bus number.
-Bus number 0 will need to be requested first, and the alias in the device
+Bus number 0 will need to be requested first, and the alias in the device
tree file will point to the correct device:
If there is no alias the devices will be numbered sequentially in the device
tree.
-The call to uclass_get_device by seq() will cause the PCI bus to be probed.
+The call to uclass_get_device() will cause the PCI bus to be probed.
This does a scan of the bus to locate available devices. These devices are
bound to their appropriate driver if available. If there is no driver, then
they are bound to a generic PCI driver which does nothing.
under that bus.
Note that this is all done on a lazy basis, as needed, so until something is
-touched on PCI it will not be probed.
+touched on PCI (eg: a call to pci_find_devices()) it will not be probed.
+
+PCI devices can appear in the flattened device tree. If they do this serves to
+specify the driver to use for the device. In this case they will be bound at
+first. Each PCI device node must have a compatible string list as well as a
+<reg> property, as defined by the IEEE Std 1275-1994 PCI bus binding document
+v2.1. Note we must describe PCI devices with the same bus hierarchy as the
+hardware, otherwise driver model cannot detect the correct parent/children
+relationship during PCI bus enumeration thus PCI devices won't be bound to
+their drivers accordingly. A working example like below:
+
+ pci {
+ #address-cells = <3>;
+ #size-cells = <2>;
+ compatible = "pci-x86";
+ u-boot,dm-pre-reloc;
+ ranges = <0x02000000 0x0 0x40000000 0x40000000 0 0x80000000
+ 0x42000000 0x0 0xc0000000 0xc0000000 0 0x20000000
+ 0x01000000 0x0 0x2000 0x2000 0 0xe000>;
+
+ pcie@17,0 {
+ #address-cells = <3>;
+ #size-cells = <2>;
+ compatible = "pci-bridge";
+ u-boot,dm-pre-reloc;
+ reg = <0x0000b800 0x0 0x0 0x0 0x0>;
+
+ topcliff@0,0 {
+ #address-cells = <3>;
+ #size-cells = <2>;
+ compatible = "pci-bridge";
+ u-boot,dm-pre-reloc;
+ reg = <0x00010000 0x0 0x0 0x0 0x0>;
+
+ pciuart0: uart@a,1 {
+ compatible = "pci8086,8811.00",
+ "pci8086,8811",
+ "pciclass,070002",
+ "pciclass,0700",
+ "x86-uart";
+ u-boot,dm-pre-reloc;
+ reg = <0x00025100 0x0 0x0 0x0 0x0
+ 0x01025110 0x0 0x0 0x0 0x0>;
+ ......
+ };
+
+ ......
+ };
+ };
+
+ ......
+ };
-PCI devices can appear in the device tree. If they do this serves to specify
-the driver to use for the device. In this case they will be bound at
-start-up.
+In this example, the root PCI bus node is the "/pci" which matches "pci-x86"
+driver. It has a subnode "pcie@17,0" with driver "pci-bridge". "pcie@17,0"
+also has subnode "topcliff@0,0" which is a "pci-bridge" too. Under that bridge,
+a PCI UART device "uart@a,1" is described. This exactly reflects the hardware
+bus hierarchy: on the root PCI bus, there is a PCIe root port which connects
+to a downstream device Topcliff chipset. Inside Topcliff chipset, it has a
+PCIe-to-PCI bridge and all the chipset integrated devices like the PCI UART
+device are on the PCI bus. Like other devices in the device tree, if we want
+to bind PCI devices before relocation, "u-boot,dm-pre-reloc" must be declared
+in each of these nodes.
+
+If PCI devices are not listed in the device tree, U_BOOT_PCI_DEVICE can be used
+to specify the driver to use for the device. The device tree takes precedence
+over U_BOOT_PCI_DEVICE. Plese note with U_BOOT_PCI_DEVICE, only drivers with
+DM_FLAG_PRE_RELOC will be bound before relocation. If neither device tree nor
+U_BOOT_PCI_DEVICE is provided, the built-in driver (either pci_bridge_drv or
+pci_generic_drv) will be used.
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projects / u-boot / blobdiff