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| author | Tom Rini <trini@konsulko.com> | 2022-06-20 10:31:28 -0400 |
|---|---|---|
| committer | Heinrich Schuchardt <heinrich.schuchardt@canonical.com> | 2022-07-13 20:07:07 +0200 |
| commit | 556af511d4731a4eaee3a6010528c3e115059ffa (patch) | |
| tree | d644bccf34b8f5fcc702c5b168e3f255ed20fa4e | |
| parent | dc6b683035560eb4be703693975168a831250476 (diff) | |
| download | u-boot-556af511d4731a4eaee3a6010528c3e115059ffa.zip u-boot-556af511d4731a4eaee3a6010528c3e115059ffa.tar.gz u-boot-556af511d4731a4eaee3a6010528c3e115059ffa.tar.bz2 | |
doc: environment: Expand on fdt_addr, initrd_addr and loadaddr
- Explain why fdt_addr and initrd_addr should not be set to disable
relocation normally.
- Provide some advice on the typical loadaddr default value.
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
| -rw-r--r-- | doc/usage/environment.rst | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst index a3f23d4..83543f6 100644 --- a/doc/usage/environment.rst +++ b/doc/usage/environment.rst @@ -204,7 +204,9 @@ fdt_high to work it must reside in writable memory, have sufficient padding on the end of it for u-boot to add the information it needs into it, and the memory - must be accessible by the kernel. + must be accessible by the kernel. This usage is strongly discouraged + however as it also stops U-Boot from ensuring the device tree starting + address is properly aligned and a misaligned tree will cause OS failures. fdtcontroladdr if set this is the address of the control flattened @@ -240,14 +242,21 @@ initrd_high memory. In this case U-Boot will NOT COPY the ramdisk at all. This may be useful to reduce the boot time on your system, but requires that this - feature is supported by your Linux kernel. + feature is supported by your Linux kernel. This usage however requires + that the user ensure that there will be no overlap with other parts of the + image such as the Linux kernel BSS. It should not be enabled by default + and only done as part of optimizing a deployment. ipaddr IP address; needed for tftpboot command loadaddr Default load address for commands like "bootp", - "rarpboot", "tftpboot", "loadb" or "diskboot" + "rarpboot", "tftpboot", "loadb" or "diskboot". Note that the optimal + default values here will vary between architectures. On 32bit ARM for + example, some offset from start of memory is used as the Linux kernel + zImage has a self decompressor and it's best if we stay out of where that + will be working. loads_echo see CONFIG_LOADS_ECHO |