Creating A devicetree.cb
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This article should help people who are writting a devicetree.cb for their system.
What you will need
While running GNU/Linux on the vendor BIOS, collect the output from:
- lspci -ntvvv
- cat /proc/ioports
If you have support for your board in serialice you may wish to gather its output also.
Reading lspci output
The Peripheral Component Interconnect (PCI) is a standerdized local bus for attaching different hardwares to motherboard.
The lspci command reads the bus information and topology, its output format is given by example:
03:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5209 PCI Express Card Reader (rev 01) +------ +---------------------- +-------------------------------------------------------------- ^ ^ ^ | | | | | Field 3: Name of device attached and its manufactured company name. | Field 2: PCI slot name. Field 1: PCI bus slot number.
The mainboard's devicetree.cb file contains many build and platform configuration settings. One of the most important items is the mainboard device list.
A device needs to be listed in the mainboard devicetree.cb if it requires more setup than standard PCI initialization (resource allocation). Typically, that includes the CPU, northbridge, southbridge, and Super I/O. These devices are usually required for system specific configuration as well as indicate the system bus structure (pci_domain).
When a device in devicetree.cb is found during the coreboot PCI/system scan process the functions to do customized initialization are called via the device_operations and the chip_operations structures. You will find these structures in the devices source files.
Keywords & Symbols
chip, device, register,on,off,pci,ioapic,pnp,i2c,lapic,cpu_cluster,domain,irq,drq,io,ioapic_irq,inherit,subsystemid,end,=
ioapic_irq: ioapic_irq number-literal pciint number-literal
rewrite this in BNF notation..
Literal values types are defined and thus consumed by the following regular expressions:
- PCI Interrupts
\"[^\"]+\" [^ \n\t]+
See source util/sconfig/sconfig.* for devicetree compiler..
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