Djam/u-boot
1
0
Fork 0
mirror of https://github.com/u-boot/u-boot.git synced 2025-04-16 18:04:48 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

doc: Update init docs for the xPL changes

Browse source 
Update the documentation here to cover the meaning of xPL

Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Simon Glass 2024-09-29 19:49:45 -06:00 • committed by Tom Rini
parent 64746bfdff
commit ac644df9a4
1 changed files with 12 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

23
doc/develop/init.rst
View file

@ -4,15 +4,16 @@ Board Initialisation Flow
-------------------------
This is the intended start-up flow for boards. This should apply for both
SPL and U-Boot proper (i.e. they both follow the same rules).
xPL and U-Boot proper (i.e. they both follow the same rules).
Note: "SPL" stands for "Secondary Program Loader," which is explained in
more detail later in this file.
Note: "xPL" stands for "any Program Loader", including SPL (Secondary
Program Loader), TPL (Tertiary Program Loader) and VPL (Verifying Program
Loader). The boot sequence is TPL->VPL->SPL->U-Boot proper
At present, SPL mostly uses a separate code path, but the function names
At present, xPL mostly uses a separate code path, but the function names
and roles of each function are the same. Some boards or architectures
may not conform to this. At least most ARM boards which use
CONFIG_SPL_FRAMEWORK conform to this.
CONFIG_xPL_FRAMEWORK conform to this.
Execution typically starts with an architecture-specific (and possibly
CPU-specific) start.S file, such as:
@ -48,7 +49,7 @@ board_init_f()
Non-xPL-specific notes:
- dram_init() is called to set up DRAM. If already done in SPL this
- dram_init() is called to set up DRAM. If already done in xPL this
can do nothing
xPL-specific notes:
@ -68,9 +69,9 @@ xPL-specific notes:
- must return normally from this function (don't call board_init_r()
directly)
Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
Here the BSS is cleared. For xPL, if CONFIG_xPL_STACK_R is defined, then at
this point the stack and global_data are relocated to below
CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
CONFIG_xPL_STACK_R_ADDR. For non-xPL, U-Boot is relocated to run at the top of
memory.
board_init_r()
@ -82,11 +83,11 @@ board_init_r()
- BSS is available, all static/global variables can be used
- execution eventually continues to main_loop()
Non-SPL-specific notes:
Non-xPL-specific notes:
- U-Boot is relocated to the top of memory and is now running from
there.
SPL-specific notes:
xPL-specific notes:
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined
- stack is optionally in SDRAM, if CONFIG_xPL_STACK_R is defined