layer-wide: define configurable default TF-A provider

TF-A package can have several providers: upstream TF-A implementation,
or NXP downstream fork. Functionality to switch this provider, and to
select which package shall be included into the target image is missing
in the layer however, defaulting the usage of the layer to NXP
downstream fork only.

Introduce the Default TF-A Provider define, make it overridable, and
default it to NXP downstream fork. This allows user to re-define the
package name later shall they choose to integrate upstream TF-A package
instead.

Current upstream TF-A version (v2.7) does not support HAB feature of
i.MX8M family, see [1]. If the upstream TF-A version is chosen, then
HAB will not be available for all SoCs that are opting-in. This is
indicated in the comment where default TF-A provider variable is set.

This might change with future TF-A release, so later it can be revised
and statement in include file can be potentially removed.

Signed-off-by: Andrey Zhizhikin <andrey.z@gmail.com>
Link: [1]: https://lists.trustedfirmware.org/archives/list/tf-a@lists.trustedfirmware.org/message/5UYYI4CNLQ5OWWHU466JBK6I5QIQ2VRS/

1 files changed, 17 insertions, 0 deletions

diff --git a/conf/machine/include/imx-base.inc b/conf/machine/include/imx-base.inc
index 67f8ed52..bb52b8d0 100644
--- a/conf/machine/include/imx-base.inc
+++ b/conf/machine/include/imx-base.inc
@@ -96,6 +96,23 @@ UBOOT_ENTRYPOINT:vf-generic-bsp     = "0x80008000"
 UBOOT_PROVIDES_BOOT_CONTAINER = "0"
 UBOOT_PROVIDES_BOOT_CONTAINER:imx-boot-container = "1"
 
+# Trusted Firmware for Cortex-A (TF-A) can have different providers, either
+# from upstream or from NXP downstream fork. Below variable defines which TF-A
+# shall be taken into the build, and will be integrated into runtime image.
+#
+# Upstream TF-A recipe resides in the meta-arm layer and in maintained by OE
+# community. Therefore, in order to add upstream TF-A - additional layer has
+# to be included in the bblayers.con file. Compatible machines are added to
+# this layer via dynamic-layers mechanism.
+#
+# NOTE: Current upstream TF-A version (v2.7) does not support HAB feature of
+# i.MX8M family. If the upstream TF-A version is chosen, then HAB will not be
+# available for all SoCs that are opting-in. This might change with future TF-A
+# release, so this statement shall be kept here until support is added.
+#
+# Default TF-A provider to NXP downstream fork
+IMX_DEFAULT_ATF_PROVIDER ??= "imx-atf"
+
 PREFERRED_PROVIDER_virtual/xserver      = "xserver-xorg"
 XSERVER_DRIVER                          = "xf86-video-fbdev"
 XSERVER_DRIVER:vf-generic-bsp           = "xf86-video-modesetting"