On 6/20/22 16:31, Tom Rini wrote:
- 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 <tr...@konsulko.com>
---
doc/usage/environment.rst | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index a3f23d4e4e22..a9a4702632d2 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.
fdt_addr_r is typically 4 byte aligned. Is there a bug in some part of
the code?
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
It is not the user but the developer who define $kernel_addr_r,
$initr_addr_r, and $fdt_addr_r.
Relocating initrd does not stop the user from loading the kernel to
initrd_high. The user is always responsible for avoiding overlap. In
this regard there is nothing special about initrd_high=~0UL.
+ iamge such as the Linux kernel BSS. It should not be enabled by default
%s/iamge/image
+ and only done as part of optimizing a deployment.
Relocating initrd and fdt is using boot time. On many boards it is
simply superfluous. On these boards I cannot see any reason not to
disable it by default.
Best regards
Heinrich
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
