Build images for RAM-only execution - #26
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Just a proof-of-concept. The new inspect_elf test seems to show that we're building the correct image. We need another commit in order to help the program run in FlexRAM.
The layout, or assignment of FlexRAM banks to memory regions, is more precise than the count. When a user specifies the count, we still apply the same layout as we always have. But now, by default, we prefer the fuse layout for users who have made no choice. This commit supports RAM loading with probe-rs. After probe-rs resets the MCU and uses the fuse FlexRAM layout, firmware can perfectly match that layout without disrupting the data already copied into RAM by the debugger.
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See #4 for details. Use the
from_ramruntime builder constructor to define a RAM-only linker script. Since most section VMAs and LMAs are equal, the MCU skips their copy.A RAM-only program that uses FlexRAM needs to, somehow, have those FlexRAM banks already configured. Furthermore, the layout, or assignment of FlexRAM banks to memory regions, needs to match. Even if the FlexRAM region capacities haven't changed, the MCU can fault if it changes the layout after placement.
This PR lets users specify the layout. If you match the FlexRAM layout to the MCU you're being loaded into, the pre-init configuration is effectively a no-op. (We could also skip the re-configuration entirely, but I still would like to keep this feature).