[PATCH v2] imx: hab: add documentation about the required keys/certs

[Claudius Heine]

For CST to find the certificates and keys for signing, some keys and
certs need to be copied into the u-boot build directory.

Signed-off-by: Claudius Heine <ch at denx.de>
---
Hi,

this patch documents some changes of the
'<20240503010518.263458-1-marex at denx.de>' patchset. So am posting it as
a reply to my earlier patch in that thread.

Changed from v1:
 - added 'symbolic link' option for making keys/certs available in build
 - `node` -> `node(s)`

---
 doc/imx/habv4/guides/mx8m_spl_secure_boot.txt | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt b/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
index ce1de659d8..75089fba4d 100644
--- a/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
+++ b/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
@@ -144,6 +144,23 @@ The signing is activated by wrapping SPL and fitImage sections into nxp-imx8mcst
 etype, which is done automatically in arch/arm/dts/imx8m{m,n,p,q}-u-boot.dtsi
 in case CONFIG_IMX_HAB Kconfig symbol is enabled.
 
+Per default the HAB keys and certificates need to be located in the build
+directory, this means creating a symbolic link or copying the following files
+from the HAB keys directory flat (e.g. removing the `keys` and `cert`
+subdirectory) into the u-boot build directory for the CST Code Signing Tool to
+locate them:
+
+- `crts/SRK_1_2_3_4_table.bin`
+- `crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem`
+- `keys/CSF1_1_sha256_4096_65537_v3_usr_key.pem`
+- `crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem`
+- `keys/IMG1_1_sha256_4096_65537_v3_usr_key.pem`
+- `keys/key_pass.txt`
+
+The paths to the SRK table and the certificates can be modified via changes to
+the nxp_imx8mcst device tree node(s), however the other files are required by
+the CST tools as well, and will be searched for in relation to them.
+
 Build of flash.bin target then produces a signed flash.bin automatically.
 
 1.4 Closing the device
-- 
2.42.0