u-boot/doc/README.falcon

1 U-Boot Falcon Mode
5 ------------
11 to boot a Linux kernel (or whatever image) without a full blown U-Boot.
14 U-Boot is split into two parts: the SPL (Secondary Program Loader) and U-Boot
15 image. In most implementations, SPL is used to start U-Boot when booting from
16 a mass storage, such as NAND or SD-Card. SPL has now support for other media,
19 copies U-Boot image into the memory.
22 from SPL. A new command is added to U-Boot to prepare the parameters that SPL
26 loading the kernel, passing to Linux the address in memory where
31 To boot the kernel, these steps under a Falcon-aware U-Boot are required:
33 1. Boot the board into U-Boot.
34 After loading the desired legacy-format kernel image into memory (and DT as
36 area or the DT.  U-Boot runs as when it boots the kernel, but stops before
39 2. Save the prepared snapshot into persistent media.
40 The address where to save it must be configured into board configuration
44 the parameters which are saved in the persistent area to the required address.
45 If a valid uImage is not found at the defined location, U-Boot will be
48 It is required to implement a custom mechanism to select if SPL loads U-Boot
55 SPL that U-Boot is not the only available image that SPL is able to start.
58 ----------------------------
60 			The command "spl export" is then available in U-Boot
62 CONFIG_SYS_SPL_ARGS_ADDR	Address in RAM where the parameters must be
75 ------------------------------------
81 		Returns "0" if SPL should start the kernel, "1" if U-Boot
85 ---------------------
91 			any other value to fall back to U-Boot (including
94 			rather than the hard-coded value.
96 			mode rather than the hard-coded value.
99 -----------------
101 spl - SPL configuration
109 		  This is the address where a kernel image is stored.
110 initrd_addr	: Address of initial ramdisk
111 		  can be set to "-" if fdt_addr without initrd_addr is used
112 fdt_addr	: in case of fdt, the address of the device tree.
121 RAM address of temporary storage. The RAM address of FDT will also be
127 Now the user have to save the generated BLOB from that printed address
128 to the pre-defined address in persistent storage
139 --------------------------------
144 device nand0 <omap2-nand.0>, # parts = 9
147  1: u-boot              0x00100000      0x00080000      0
162 Now the kernel is in RAM at address 0x82000000
166    Image Name:   Linux-3.5.0-rc4-14089-gda0b7f4
169    Load Address: 80008000
178 The result can be checked at address 0x80000100:
191 Now the parameters are stored into the NAND flash at the address
197 The kernel is loaded directly by the SPL without passing through U-Boot.
200 -------------------------------
203 prepard/patched first. U-Boot usually inserts some dynamic values into
204 the DT binary (blob), e.g. autodetected memory size, MAC addresses,
222 5. Save fdt to NOR flash: