Introduction:
-------------
The AM65x family of SoCs is the first device family from K3 Multicore
SoC architecture, targeted for broad market and industrial control with
aim to meet the complex processing needs of modern embedded products.

The device is built over three domains, each containing specific processing
cores, voltage domains and peripherals:
1. Wake-up (WKUP) domain:
	- Device Management and Security Controller (DMSC)
2. Microcontroller (MCU) domain:
	- Dual Core ARM Cortex-R5F processor
3. MAIN domain:
	- Quad core 64-bit ARM Cortex-A53

More info can be found in TRM: http://www.ti.com/lit/pdf/spruid7

Boot Flow:
----------
On AM65x family devices, ROM supports boot only via MCU(R5). This means that
bootloader has to run on R5 core. In order to meet this constraint, and for
the following reasons the boot flow is designed as mentioned:
1. Need to move away from R5 asap, so that we want to start *any*
firmware on the r5 cores like.... autosar can be loaded to receive CAN
response and other safety operations to be started. This operation is
very time critical and is applicable for all automotive use cases.
2. U-Boot on A53 should start other remotecores for various
applications. This should happen before running Linux.
3. In production boot flow, we might not like to use full u-boot,
instead use Flacon boot flow to reduce boot time.

+------------------------------------------------------------------------+
|        DMSC            |         R5            |        A53            |
+------------------------------------------------------------------------+
|    +--------+          |                       |                       |
|    |  Reset |          |                       |                       |
|    +--------+          |                       |                       |
|         :              |                       |                       |
|    +--------+          |   +-----------+       |                       |
|    | *rom*  |----------|-->| Reset rls |       |                       |
|    +--------+          |   +-----------+       |                       |
|    |        |          |         :             |                       |
|    |  rom   |          |         :             |                       |
|    |services|          |         :             |                       |
|    |        |          |   +-------------+     |                       |
|    |        |          |   |  *R5 rom*   |     |                       |
|    |        |          |   +-------------+     |                       |
|    |        |<---------|---|Load and auth|     |                       |
|    |        |          |   | tiboot3.bin |     |                       |
|    |        |          |   +-------------+     |                       |
|    |        |          |         :             |                       |
|    |        |          |         :             |                       |
|    |        |          |         :             |                       |
|    |        |          |   +-------------+     |                       |
|    | Start  |          |   |  *R5 SPL*   |     |                       |
|    | System |          |   +-------------+     |                       |
|    |Firmware|<---------|---|Load and auth|     |                       |
|    +--------+          |   |  sysfw bin  |     |                       |
|        :               |   +-------------+     |                       |
|    +---------+         |   |     DDR     |     |                       |
|    | *SYSFW* |         |   |    config   |     |                       |
|    +---------+         |   +-------------+     |                       |
|    |         |<--------|---|    Load     |     |                       |
|    |         |         |   |  tispl.bin  |     |                       |
|    |         |         |   +-------------+     |                       |
|    |         |<--------|---| Start A53   |     |                       |
|    |         |         |   |  and Reset  |     |                       |
|    |         |         |   +-------------+     |                       |
|    |         |         |                       |     +-----------+     |
|    |         |---------|-----------------------|---->| Reset rls |     |
|    |         |         |                       |     +-----------+     |
|    |  DMSC   |         |                       |          :            |
|    |Services |         |                       |     +-----------+     |
|    |         |<--------|-----------------------|---->|*ATF/OPTEE*|     |
|    |         |         |                       |     +-----------+     |
|    |         |         |                       |          :            |
|    |         |         |                       |     +-----------+     |
|    |         |<--------|-----------------------|---->| *A53 SPL* |     |
|    |         |         |                       |     +-----------+     |
|    |         |         |                       |     |   Load    |     |
|    |         |         |                       |     | u-boot.img|     |
|    |         |         |                       |     +-----------+     |
|    |         |         |                       |          :            |
|    |         |         |                       |     +-----------+     |
|    |         |<--------|-----------------------|---->| *u-boot*  |     |
|    |         |         |                       |     +-----------+     |
|    |         |         |                       |     |  prompt   |     |
|    |         |         |                       |     +-----------+     |
|    +---------+         |                       |                       |
|                        |                       |                       |
+------------------------------------------------------------------------+

- Here DMSC acts as master and provides all the critical services. R5/A53
requests DMSC to get these services done as shown in the above diagram.

Sources:
--------
1. SYSFW:
	System Firmware repo is closed source and the binaries are delivered
	to users with NDA. Please contact TI to get the System Firmware
	Binary named ti-sci-firmware-am6x.bin that runs on AM65x SoC.

2. ATF:
	Tree: https://github.com/ARM-software/arm-trusted-firmware.git
	Branch: master

3. OPTEE:
	Tree: https://github.com/OP-TEE/optee_os.git
	Branch: master

4. U-Boot:
	Tree: http://git.denx.de/u-boot.git
	Branch: master

Build procedure:
----------------
1. SYSFW:
	ROM expects a signed binary that contains the X509 certificate. So
the binary ti-sci-firmware-am6x.bin cannot be uses as-is and needs to be signed.
Contact TI on the procedure to sign the system firmware binary.

2. ATF:
$ make CROSS_COMPILE=aarch64-linux-gnu- ARCH=aarch64 PLAT=k3 TARGET_BOARD=generic SPD=opteed

3. OPTEE:
$ make PLATFORM=k3-am65x CFG_ARM64_core=y

4. U-Boot:

4.1. R5:
	TBD.

4.2. A53:
$ make ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- am65x_evm_a53_defconfig O=/tmp/a53
$ make ARCH=arm CROSS_COMPILE=aarch64-linux-gnu-  ATF=<path to ATF dir>/build/k3/generic/release/bl31.bin TEE=<path to OPTEE OS dir>/out/arm-plat-k3/core/tee-pager.bin O=/tmp/a53

Target Images
--------------
Copy the below images to an SD card and boot:
- tiboot3.bin from step 4.1
- tispl.bin, u-boot.img from 4.2