u-boot/doc/device-tree-bindings/pci/x86-pci.txt
Simon Glass d8c7fb5036 dm: pci: Allow disabling auto-config for a device
Add a means to avoid configuring a device when needed. Add an explanation
of why this is useful to the binding file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
2020-04-16 14:36:28 +08:00

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x86 PCI DT details:
===================
Some options are available to affect how PCI operates on x86.
Optional properties:
- u-boot,skip-auto-config-until-reloc : Don't set up PCI configuration until
after U-Boot has relocated. Normally if PCI is used before relocation,
this happens before relocation also. Some platforms set up static
configuration in TPL/SPL to reduce code size and boot time, since these
phases only know about a small subset of PCI devices.
For PCI devices the following optional property is available:
- pci,no-autoconfig : Don't automatically configure this PCI device at all.
This is used when the device is statically configured and must maintain
this same config throughout the boot process. An example is a serial
UART being used to debug PCI configuration, since reconfiguring it stops
the UART from working until the driver is re-probed, and this can cause
output to be lost. This should not generally be used in production code,
although it is often harmless.
Example:
pci {
compatible = "pci-x86";
#address-cells = <3>;
#size-cells = <2>;
u-boot,dm-pre-reloc;
ranges = <0x02000000 0x0 0xc0000000 0xc0000000 0 0x10000000
0x42000000 0x0 0xb0000000 0xb0000000 0 0x10000000
0x01000000 0x0 0x1000 0x1000 0 0xefff>;
u-boot,skip-auto-config-until-reloc;
serial: serial@18,2 {
reg = <0x0200c210 0 0 0 0>;
u-boot,dm-pre-reloc;
compatible = "intel,apl-ns16550";
early-regs = <0xde000000 0x20>;
reg-shift = <2>;
clock-frequency = <1843200>;
current-speed = <115200>;
pci,no-autoconfig;
};
};