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doc: Update init docs for the xPL changes

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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
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23
doc/develop/init.rst
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@@ -4,15 +4,16 @@ Board Initialisation Flow
------------------------- -------------------------
This is the intended start-up flow for boards. This should apply for both 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 Note: "xPL" stands for "any Program Loader", including SPL (Secondary
more detail later in this file. 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 and roles of each function are the same. Some boards or architectures
may not conform to this. At least most ARM boards which use 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 Execution typically starts with an architecture-specific (and possibly
CPU-specific) start.S file, such as: CPU-specific) start.S file, such as:
@@ -48,7 +49,7 @@ board_init_f()
Non-xPL-specific notes: 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 can do nothing
xPL-specific notes: xPL-specific notes:
@@ -68,9 +69,9 @@ xPL-specific notes:
- must return normally from this function (don't call board_init_r() - must return normally from this function (don't call board_init_r()
directly) 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 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. memory.
board_init_r() board_init_r()
@@ -82,11 +83,11 @@ board_init_r()
- BSS is available, all static/global variables can be used - BSS is available, all static/global variables can be used
- execution eventually continues to main_loop() - 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 - U-Boot is relocated to the top of memory and is now running from
there. 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