.. SPDX-License-Identifier: GPL-2.0+
.. sectionauthor:: Jan Kiszka <jan.kiszka@siemens.com>

SIMATIC IOT2050 BASIC and ADVANCED
==================================

The SIMATIC IOT2050 is an open industrial IoT gateway that is using the TI
AM6528 GP (Basic variant) or the AM6548 HS (Advanced variant). The Advanced
variant is prepared for secure boot. M.2 Variant also uses the AM6548 HS.
Instead of a MiniPCI connector, it comes with two M.2 connectors and can
support 5G/WIFI/BT applications or connect an SSD. Compared with the AM6548
Advanced variant, SM variant removes the Arduino interface, and adds a new
ASIC for communicating with the PLC 1200 signal modules.

The IOT2050 starts only from OSPI. It loads a Siemens-provided bootloader
called SE-Boot for the MCU domain (R5F cores), then hands over to ATF and
OP-TEE, before booting U-Boot on the A53 cores. This describes how to build all
open artifacts into a flashable image for the OSPI flash. The flash image will
work on both variants.

Dependencies
------------

ATF:    Upstream release 2.4 or newer
OP-TEE: Upstream release 3.10.0 or newer

Binary dependencies can be found in
https://github.com/siemens/meta-iot2050/tree/master/recipes-bsp/u-boot/files/prebuild.
The following binaries from that source need to be present in the build folder:

 - seboot_pg1.bin
 - seboot_pg2.bin

Note that SE-Boot D/V01.04.01.02 or greater is required, otherwise the DDR size
will not be picked up correctly by U-Boot.

When using the watchdog, a related firmware for the R5 core(s) is needed, e.g.
https://github.com/siemens/k3-rti-wdt. The name and location of the image is
configured via CONFIG_WDT_K3_RTI_FW_FILE.

For building an image containing the OTP key provisioning data, below binary
needs to be present in the build folder:

 - otpcmd.bin

Regarding how to generating this otpcmd.bin, please refer to:
https://github.com/siemens/meta-iot2050/tree/master/recipes-bsp/secure-boot-otp-provisioning/files/make-otpcmd.sh

Building
--------

Make sure that CROSS_COMPILE is set appropriately:

.. code-block:: text

 $ export CROSS_COMPILE=aarch64-linux-gnu-

ATF:

.. code-block:: text

 $ make PLAT=k3 SPD=opteed K3_USART=1

OP-TEE:

.. code-block:: text

 $ make PLATFORM=k3-am65x CFG_ARM64_core=y CFG_TEE_CORE_LOG_LEVEL=2 CFG_CONSOLE_UART=1 CFG_USER_TA_TARGETS="ta_arm64"

U-Boot:

.. code-block:: text

 $ export BL31=/path/to/bl31.bin
 $ export TEE=/path/to/tee-raw.bin
 $ make iot2050_defconfig

 $ make

This will generate two different flash images: flash-p1.bin that targets the
first generation of IOT2050 devices and flash-pg2.bin that runs on PG2
including M.2 devices.

Flashing
--------

Via U-Boot:

.. code-block:: text

 IOT2050> sf probe
 IOT2050> load mmc 0:1 $loadaddr /path/to/flash-pgX.bin
 IOT2050> sf update $loadaddr 0x0 $filesize

Via external programmer Dediprog SF100 or SF600:

.. code-block:: text

 $ dpcmd --vcc 2 -v -u flash-pgX.bin

Signing (optional)
------------------

To enable verified boot for the firmware artifacts after the Siemens-managed
first-stage loader (seboot_pgX.bin), the following steps need to be taken
before and after the build:

Generate dtsi holding the public key
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: text

 tools/key2dtsi.py -c -s key.pem public-key.dtsi

This will be used to embed the public key into U-Boot SPL and main so that each
step can validate signatures of the succeeding one.

Adjust U-Boot configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Enabled at least the following options in U-Boot:

.. code-block:: text

 CONFIG_SPL_FIT_SIGNATURE=y
 CONFIG_DEVICE_TREE_INCLUDES="/path/to/public-key.dtsi"
 CONFIG_RSA=y

Note that there are more configuration changes needed in order to lock-down
the command line and the boot process of U-Boot for secure scenarios. These are
not in scope here.

Build U-Boot
^^^^^^^^^^^^

See related section above.

Sign flash-pgX.bin
^^^^^^^^^^^^^^^^^^

In the build folder still containing artifacts from step 3, invoke:

.. code-block:: text

 tools/iot2050-sign-fw.sh /path/to/key.pem

Flash signed flash-pgX.bin
^^^^^^^^^^^^^^^^^^^^^^^^^^

The signing has happen in-place in flash-pgX.bin, thus the flashing procedure
described above.

M.2 slot configuration
----------------------

The M.2 variant of the IOT2050 comes with one B-keyed and one E-keyed slot.
These are configured by U-Boot depending on the detected usage (auto
configuration). The device tree loaded later on for the OS will be fixed up
by U-Boot according to this configuration.

For the case auto configuration does not work reliably, it is possible to set
the U-Boot environment variable "m2_manual_config" to select the mode manually:

"0"  -  B-key: PCIe x2, USB 2.0
        E-key: USB 2.0
"1"  -  B-key: PCIe, USB 2.0
        E-key: PCIe, USB 2.0
"2"  -  B-key: USB 3.0,
        E-key: PCIe, USB 2.0
