[PATCH 5/5 v2] doc: uefi.rst: Add OP-TEE variable storage config options

Ilias Apalodimas ilias.apalodimas at linaro.org
Mon May 11 20:14:03 CEST 2020

If OP-TEE is compiled with an EDK2 application running in secure world
it can process and store UEFI variables in an RPMB.
Add documentation for the config options enabling this

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
 doc/uefi/uefi.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst
index 4fda00d68721..03d6fd0c6aa8 100644
--- a/doc/uefi/uefi.rst
+++ b/doc/uefi/uefi.rst
@@ -188,6 +188,23 @@ on the sandbox
     cd <U-Boot source directory>
     pytest.py test/py/tests/test_efi_secboot/test_signed.py --bd sandbox
+Using OP-TEE for EFI variables
+Instead of implementing UEFI variable services inside U-Boot they can
+also be provided in the secure world by a module for OP-TEE[1]. The
+interface between U-Boot and OP-TEE for variable services is enabled by
+Tianocore EDK II's standalone management mode driver for variables can
+be linked to OP-TEE for this purpose. This module uses the Replay
+Protected Memory Block (RPMB) of an eMMC device for persisting
+non-volatile variables. When calling the variable services via the
+OP-TEE API U-Boot's OP-TEE supplicant relays calls to the RPMB driver
+which has to be enabled via CONFIG_SUPPORT_EMMC_RPMB=y.
+[1] https://optee.readthedocs.io/ - OP-TEE documentation
 Executing the boot manager

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