[PATCH 1/1] doc: U-Boot boot phases

[Conor Dooley]

Hey Heinrich,

On Fri, Jul 28, 2023 at 05:48:31PM +0200, Heinrich Schuchardt wrote:
> 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 at canonical.com>
> ---
>  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.

I think you need to add a comma here after SPL. I had to read this a few
times before it made sense to me!

>  
>  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
>  -----------------------
> -- 
> 2.40.1
> 
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