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zephyrproject-rtos / zephyr

Primary Git Repository for the Zephyr Project. Zephyr is a new generation, scalable, optimized, secure RTOS for multiple hardware architectures.
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using both retram and mcusram for code on stm32mp1 platforms #64793

Closed shlomow closed 9 months ago

shlomow commented 9 months ago

Currently, zephyr uses retram for code for stm32mp1 platforms, which is limited to 64 KB. Is there a way to add also mcusram for code?

erwango commented 9 months ago

^^@arnopo

arnopo commented 9 months ago

@shlomow The main issue is that the RETRAM and the MCU SRAM are not contigious RETRAM @ address 0, size 64 kB MCU SRAM address 0x10000000 (aliased at 0x30000000) size 384 kB

The 2nd constraint is that the Cortex-M4 boots at address 0x00000000 of the RETRAM so at least the vector table should be linked at address 0x00000000

You will need a custom linker to adapt the memory mapping

shlomow commented 9 months ago

Thanks @arnopo! Can you please share where in zephyr linker scripts I need to make this change?

arnopo commented 9 months ago

I created a POC a long time ago. That define the vectore table in the RETRAM and then use only MCU SRAM for code and data. Perhaps it could inspire you. https://github.com/arnopo/zephyr_stm32mp1/commits/linker_poc This POC is probably not up to date but I have nothing more recent.

Another approach is to use --enable-non-contiguous-regions option that has been introduced in GNU GCC to support of non-contiguous regions. I did not test it but should help to split code between RETRAM and MCU SRAM: https://manpages.ubuntu.com/manpages/jammy/man1/ld.1.html#:~:text=%2D%2Denable%2Dnon%2Dcontiguous%2D,output%20section%20is%20large%20enough.

shlomow commented 9 months ago

Thanks @arnopo! Your branch from 2019 does exactly the changes I need. The only change I made is renaming _image_rom_start to __rom_region_start. Thanks again!