Add more detail to the description of U-Boot boot phases:
* describe which steps are optional * mentions alternative boot flows
Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com Reviewed-by: Bin Meng bmeng.cn@gmail.com --- v2: add missing comma --- doc/develop/spl.rst | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/doc/develop/spl.rst b/doc/develop/spl.rst index a1515a7b43..5743bdf37c 100644 --- a/doc/develop/spl.rst +++ b/doc/develop/spl.rst @@ -77,10 +77,11 @@ To check whether a feature is enabled, use CONFIG_IS_ENABLED():: This checks CONFIG_CLK for the main build, CONFIG_SPL_CLK for the SPL build, CONFIG_TPL_CLK for the TPL build, etc.
-U-Boot Phases -------------- +U-Boot Boot Phases +------------------
-U-Boot boots through the following phases: +U-Boot goes through the following boot phases where TPL, VPL, SPL are optional. +While many boards use SPL, less use TPL.
TPL Very early init, as tiny as possible. This loads SPL (or VPL if enabled). @@ -97,6 +98,12 @@ SPL U-Boot U-Boot proper, containing the command line and boot logic.
+Further usages of U-Boot SPL comprise: + +* Launching BL31 of ARM Trusted Firmware which invokes main U-Boot as BL33 +* launching EDK II +* launching Linux kernel +* launching RISC-V OpenSBI which invokes main U-Boot
Checking the boot phase -----------------------