Neha Francis <n-francis@ti.com>
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:
- Wake-up (WKUP) domain:
- Device Management and Security Controller (DMSC)
- Microcontroller (MCU) domain:
- Dual Core ARM Cortex-R5F processor
- MAIN domain:
- Quad core 64-bit ARM Cortex-A53
More info can be found in TRM: https://www.ti.com/lit/pdf/spruid7
Platform information:
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 for example 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 Falcon boot flow to reduce boot time.
- 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.
- Setup the environment variables:
Set the variables corresponding to this platform:
bash $
export UBOOT_CFG_CORTEXR=am65x_evm_r5_defconfig export UBOOT_CFG_CORTEXA=am65x_evm_a53_defconfig export TFA_BOARD=generic # we dont use any extra TFA parameters unset TFA_EXTRA_ARGS export OPTEE_PLATFORM=k3-am65x # we dont use any extra OP-TEE parameters unset OPTEE_EXTRA_ARGS
- Trusted Firmware-A:
- OP-TEE:
- U-Boot:
- 3.1 R5:
- 3.2 A53:
In order to boot we need tiboot3.bin, sysfw.itb, tispl.bin and u-boot.img. Each SoC variant (GP and HS) requires a different source for these files.
GP
- tiboot3-am65x_sr2-gp-evm.bin, sysfw-am65x_sr2-gp-evm.itb from step 3.1
- tispl.bin_unsigned, u-boot.img_unsigned from step 3.2
HS
- tiboot3-am65x_sr2-hs-evm.bin, sysfw-am65x_sr2-hs-evm.itb from step 3.1
- tispl.bin, u-boot.img from step 3.2
- tiboot3.bin
- tispl.bin
- sysfw.itb
ROM supports booting from eMMC from boot0 partition offset 0x0
Flashing images to eMMC:
The following commands can be used to download tiboot3.bin, tispl.bin, u-boot.img, and sysfw.itb from an SD card and write them to the eMMC boot0 partition at respective addresses.
bash =>
mmc dev 0 1 fatload mmc 1 ${loadaddr} tiboot3.bin mmc write ${loadaddr} 0x0 0x400 fatload mmc 1 ${loadaddr} tispl.bin mmc write ${loadaddr} 0x400 0x1000 fatload mmc 1 ${loadaddr} u-boot.img mmc write ${loadaddr} 0x1400 0x2000 fatload mmc 1 ${loadaddr} sysfw.itb mmc write ${loadaddr} 0x3600 0x800
To give the ROM access to the boot partition, the following commands must be used for the first time:
bash =>
mmc partconf 0 1 1 1 mmc bootbus 0 1 0 0
To create a software partition for the rootfs, the following command can be used:
bash =>
gpt write mmc 0 ${partitions}
eMMC layout:
Kernel image and DT are expected to be present in the /boot folder of rootfs. To boot kernel from eMMC, use the following commands:
bash =>
setenv mmcdev 0 setenv bootpart 0 boot
ROM supports booting from OSPI from offset 0x0.
Flashing images to OSPI:
Below commands can be used to download tiboot3.bin, tispl.bin, u-boot.img, and sysfw.itb over tftp and then flash those to OSPI at their respective addresses.
bash =>
sf probe tftp ${loadaddr} tiboot3.bin sf update $loadaddr 0x0
Flash layout for OSPI:
Kernel Image and DT are expected to be present in the /boot folder of UBIFS ospi.rootfs just like in SD card case. U-Boot looks for UBI volume named "rootfs" for rootfs.
To boot kernel from OSPI, at the U-Boot prompt:
bash =>
setenv boot ubi boot
ROM supports booting from MCU_UART0 via X-Modem protocol. The entire UART-based boot process up to U-Boot (proper) prompt goes through different stages and uses different UART peripherals as follows:
ROM UART Boot Responsibilities| Who | Loading What | Hardware Module | Protocol |
|---|---|---|---|
| Boot ROM | tiboot3.bin | MCU_UART0 | X-Modem(*) |
| R5 SPL | sysfw.itb | MCU_UART0 | Y-Modem(*) |
| R5 SPL | tispl.bin | MAIN_UART0 | Y-Modem |
| A53 SPL | u-boot.img | MAIN_UART0 | Y-Modem |
Note that in addition to X/Y-Modem related protocol timeouts the DMSC watchdog timeout of 3min (typ.) needs to be observed until System Firmware is fully loaded (from sysfw.itb) and started.
Example bash script sequence for running on a Linux host PC feeding all boot artifacts needed to the device:
bash $
MCU_DEV=/dev/ttyUSB1 MAIN_DEV=/dev/ttyUSB0
stty -F $MCU_DEV 115200 cs8 -cstopb -parenb stty -F $MAIN_DEV 115200 cs8 -cstopb -parenb
sb --xmodem tiboot3.bin > $MCU_DEV < $MCU_DEV sb --ymodem sysfw.itb > $MCU_DEV < $MCU_DEV sb --ymodem tispl.bin > $MAIN_DEV < $MAIN_DEV sleep 1 sb --xmodem u-boot.img > $MAIN_DEV < $MAIN_DEV
See Common Debugging environment - OpenOCD<k3_rst_refer_openocd>: for detailed setup information.
Warning
OpenOCD support since: v0.12.0
If the default package version of OpenOCD in your development environment's distribution needs to be updated, it might be necessary to build OpenOCD from the source.
To start OpenOCD and connect to the board
bash $
openocd -f board/ti_am654evm.cfg