[bootlin/training-materials updates] master: labs/sysdev-u-boot-stm32: add more details (d48580f1)

[Thomas Petazzoni]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/d48580f12e8255bb5d9509c2312c9dd8167d8fb4

>---------------------------------------------------------------

commit d48580f12e8255bb5d9509c2312c9dd8167d8fb4
Author: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
Date:   Thu Sep 22 14:56:21 2022 +0200

    labs/sysdev-u-boot-stm32: add more details
    
    (1) Explain that the FIP image needs to be re-generated/reflashed
    after changing the U-Boot configuration
    
    (2) Add a small section on playing around with the U-Boot environment.
    
    Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>


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d48580f12e8255bb5d9509c2312c9dd8167d8fb4
 labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex b/labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex
index 9f0c1781..62274bb8 100644
--- a/labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex
+++ b/labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex
@@ -381,8 +381,28 @@ allows to dump the configuration settings U-Boot was compiled from.
 
 If it's not, go back to U-Boot's configuration and enable it.
 
-Update U-Boot on the SD card and test that the command is now
-available and works as expected.
+Re-run the build of U-Boot, and then re-run the build of TF-A so that
+a new version of the \code{fip.bin} with the updated U-Boot is
+generated.
+
+Update the \code{fip} partition on the SD card with the new
+\code{fip.bin} image and test that the command is now available and
+works as expected.
+
+\subsection{Playing with the U-Boot environment}
+
+Display the U-Boot environment using \code{printenv}.
+
+Set a new U-Boot variable \code{foo} to a value of your choice, using
+\code{setenv}, and verify it has been set. Reset the board, and check
+if \code{foo} is still defined: it should not.
+
+Now repeat this process, but before resetting the board, use
+\code{saveenv}. After the reset, check the \code{foo} variable is
+still defined.
+
+Now reset the environment to its default settings using \code{env
+  default -a}, and save these changes using \code{saveenv}.
 
 \section{Setting up Ethernet communication}