[FAQ] TDA4VM: How to build SBL in debug mode j721e RTOS SDK?

Hi,

The size of SBL needs to be restricted due to memory restrictions posed by limited OCMC. Typically, OCMC needs to fit both SBL and firmware. Building in debug mode generally increases the size of binaries and there is a risk it might go beyond available memory. That’s why, by default, debug mode is disabled for SBL

Although, there are some ways to build SBL for debugging:

1) Enabling the debug mode

You can enable the debug mode by modifying the sbl_component.mk at <pdkInstallPath>\packages\ti\boot\sbl\ .  See the patches below:

1. sblComponent_8_0.patch
2. sblComponent_8_1.patch

Save and build the SBL using the command

gmake BOARD=j721e_evm CORE=mcu1_0 BUILD_RPOFILE=debug sbl_{BootMode}_img

where BootMode can be uart, mmcsd, ospi, cust

This approach will give you complete control over SBL during debug, but this may fail in future releases, if the size of SBL increases for some reason This has been tested on j721e RTOS SDK 8.0 and 8.1.

2) Building specific components in debug mode

Instead of building the complete SBL in debug mode, you can build specific components which you need to debug and link them to SBL to keep the size of SBL in check. The easiest way to this is to build the component in debug mode using BUILD_PROFILE flag and then renaming the debug library as release.

For example, if you want to debug “board”:

1. gmake board BOARD=j721e_evm CORE=mcu1_0 BUILD_PROFILE=debug
2. Rename <pdkInstallPath>\packages\ti\board\lib\j721e_evm\r5f\debug to <pdkInstallPath>\packages\ti\board\lib\j721e_evm\r5f\release
3. Build the SBL image using

gmake BOARD=j721e_evm CORE=mcu1_0 sbl_{BootMode}_img

This approach will keep the size of SBL in check and give you more control over the components built in debug mode, but you still won’t be able to single step through SBL code.

3) Removing compiler optimizations and rebuilding specific components

This is similar to previous approach, but it will give you control over SBL code as well. You can remove the compiler optimization by modifying <pdkInstallPath>\packages\ti\build\makerules\rules_ti_cgt_arm.mk . See the patch below.

1. rules_ti_cgt_arm_8_0.patch
2. rules_ti_cgt_arm_8_1.patch

Once the compiler optimization is removed, just rebuild the components you want to debug and the SBL release mode. This will give you control over the component and the SBL during debug.

Please make sure to restore the optimizations once the debug is done, as it may affect the performance of your application.

Regards,
Parth