doc: boards: amlogic: update documentation for S400

Improve documentation.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Link: https://lore.kernel.org/r/20230320114609.930145-25-christianshewitt@gmail.com
[narmstrong: fixed doc build]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

doc/board/amlogic/s400.rst

@@ -1,15 +1,14 @@
 .. SPDX-License-Identifier: GPL-2.0+
 
-U-Boot for Amlogic S400
-=======================
+U-Boot for Amlogic S400 (A113X)
+===============================
 
-S400 is a reference board manufactured by Amlogic with the following
-specifications:
+S400 is a reference board manufactured by Amlogic with the following specifications:
 
- - Amlogic A113DX ARM Cortex-A53 quad-core SoC @ 1.2GHz
+ - Amlogic A113X ARM Cortex-A53 quad-core SoC @ 1.2GHz
  - 1GB DDR4 SDRAM
  - 10/100 Ethernet
- - 2 x USB 2.0 Host
+ - 2x USB 2.0 Host
  - eMMC
  - Infrared receiver
  - SDIO WiFi Module
@@ -19,7 +18,7 @@ specifications:
 
 Schematics are available from Amlogic on demand.
 
-U-Boot compilation
+U-Boot Compilation
 ------------------
 
 .. code-block:: bash
@@ -28,14 +27,21 @@ U-Boot compilation
     $ make s400_defconfig
     $ make
 
-Image creation
---------------
+U-Boot Signing with Pre-Built FIP repo
+--------------------------------------
 
-For simplified usage, pleaser refer to :doc:`pre-generated-fip` with codename `s400`
+.. code-block:: bash
 
-Amlogic doesn't provide sources for the firmware and for tools needed
-to create the bootloader image, so it is necessary to obtain them from
-the git tree published by the board vendor:
+    $ git clone https://github.com/LibreELEC/amlogic-boot-fip --depth=1
+    $ cd amlogic-boot-fip
+    $ mkdir my-output-dir
+    $ ./build-fip.sh s400 /path/to/u-boot/u-boot.bin my-output-dir
+
+U-Boot Manual Signing
+---------------------
+
+Amlogic does not provide sources for the firmware and tools needed to create a bootloader
+image but sources have been shared by Linux development contractor, Baylibre:
 
 .. code-block:: bash
 
@@ -65,47 +71,47 @@ Go back to mainline U-boot source tree then :
     $ cp u-boot.bin fip/bl33.bin
 
     $ $FIPDIR/blx_fix.sh \
-    	fip/bl30.bin \
-    	fip/zero_tmp \
-    	fip/bl30_zero.bin \
-    	fip/bl301.bin \
-    	fip/bl301_zero.bin \
-    	fip/bl30_new.bin \
-    	bl30
+              fip/bl30.bin \
+              fip/zero_tmp \
+              fip/bl30_zero.bin \
+              fip/bl301.bin \
+              fip/bl301_zero.bin \
+              fip/bl30_new.bin \
+              bl30
 
     $ $FIPDIR/acs_tool.pyc fip/bl2.bin fip/bl2_acs.bin fip/acs.bin 0
 
     $ $FIPDIR/blx_fix.sh \
-    	fip/bl2_acs.bin \
-    	fip/zero_tmp \
-    	fip/bl2_zero.bin \
-    	fip/bl21.bin \
-    	fip/bl21_zero.bin \
-    	fip/bl2_new.bin \
-    	bl2
+              fip/bl2_acs.bin \
+              fip/zero_tmp \
+              fip/bl2_zero.bin \
+              fip/bl21.bin \
+              fip/bl21_zero.bin \
+              fip/bl2_new.bin \
+              bl2
 
     $ $FIPDIR/axg/aml_encrypt_axg --bl3sig --input fip/bl30_new.bin \
-    					--output fip/bl30_new.bin.enc \
-    					--level v3 --type bl30
+                                           --output fip/bl30_new.bin.enc \
+                                           --level v3 --type bl30
     $ $FIPDIR/axg/aml_encrypt_axg --bl3sig --input fip/bl31.img \
-    					--output fip/bl31.img.enc \
-    					--level v3 --type bl31
+                                           --output fip/bl31.img.enc \
+                                           --level v3 --type bl31
     $ $FIPDIR/axg/aml_encrypt_axg --bl3sig --input fip/bl33.bin --compress lz4 \
-    					--output fip/bl33.bin.enc \
-    					--level v3 --type bl33
+                                           --output fip/bl33.bin.enc \
+                                           --level v3 --type bl33
     $ $FIPDIR/axg/aml_encrypt_axg --bl2sig --input fip/bl2_new.bin \
-    					--output fip/bl2.n.bin.sig
+                                           --output fip/bl2.n.bin.sig
     $ $FIPDIR/axg/aml_encrypt_axg --bootmk \
-    		--output fip/u-boot.bin \
-    		--bl2 fip/bl2.n.bin.sig \
-    		--bl30 fip/bl30_new.bin.enc \
-    		--bl31 fip/bl31.img.enc \
-    		--bl33 fip/bl33.bin.enc --level v3
+                                  --output fip/u-boot.bin \
+                                  --bl2 fip/bl2.n.bin.sig \
+                                  --bl30 fip/bl30_new.bin.enc \
+                                  --bl31 fip/bl31.img.enc \
+                                  --bl33 fip/bl33.bin.enc --level v3
 
-and then write the image to SD with:
+Then write U-Boot to SD or eMMC with:
 
 .. code-block:: bash
 
-    $ DEV=/dev/your_sd_device
+    $ DEV=/dev/boot_device
     $ dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=512 skip=1 seek=1
-    $ dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=1 count=444
+    $ dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=1 count=440