UlasSertan opened a new pull request, #20105:
URL: https://github.com/apache/nuttx/pull/20105
### Summary
* Marking the DDR region Shareable makes `LDREX`/`STREX` to it take an
external data abort on this Cortex-R5F: there is no external exclusive
monitor on the path to DDR.
* Non-shareable makes exclusives use the core-local monitor instead.
* Every atomic on this chip compiles to inline LDREX/STREX: it selects no
`LIBC_ATOMIC_*` backend and falls back to `LIBC_ATOMIC_TOOLCHAIN`. The
abort
therefore lands during early startup, before the console is up.
* Drops `MPU_RACR_S` from `am67_ddr_region`.
### Impact
* Is new feature added? Is existing feature changed? **YES** — changes the
MPU
attributes of the AM67 DDR region.
* Impact on user? **NO** — AM67 only, and the previous setting was
unusable.
* Impact on build? **NO**.
* Impact on hardware? **YES** — arch/arm/am67 only.
* Impact on documentation? **NO**.
* Impact on security? **NO**.
* Impact on compatibility? **NO** — no external API or Kconfig change.
* Anything else? No dependency on other PRs in this series.
### Testing
```
Build Host(s): Pardus GNU/Linux 25 (Debian 13 base), x86_64, host gcc 14
Toolchain: arm-none-eabi-gcc 14.2.1 20241119 (15:14.2.rel1-1)
Target: arm / TI AM67 (J722S) Cortex-R5F, board t3-gem-o1:nsh
nuttx-apps: 5a7ab4200
Loaded on the main-domain R5F by Linux remoteproc; console on UART-MAIN1.
```
Testing logs before change: the image loads and remoteproc reports the core
running, but the console stays silent — the abort happens before it comes up,
so there is no output to capture:
```
$ ssh <board> 'cat /sys/class/remoteproc/remoteprocN/state'
running
$ # UART-MAIN1: no output at all
```
The version string in the logs is from the tested build; the commits were
GPG-signed afterwards, which rewrites hashes. The code is unchanged.
Testing logs after change:
```
make distclean && ./tools/configure.sh t3-gem-o1:nsh && make -j
-> nuttx ELF 511900 bytes, 0 compiler warnings
Console:
user_main: Exiting
ostest_main: Exiting with status 0
Test plan result:
console_alive PASS prompt responsive
version PASS NuttX version 0.0.0 3b52393af4 Sep 10 2026
13:47:18 t3-gem-o1:nsh
procfs PASS procfs readable
tasks PASS 2 task lines
heap_baseline PASS used=6672
ostest PASS clean, status 0
heap_after_ostest PASS delta +232 bytes
PASS=7
```
### PR verification Self-Check
* [x] This PR introduces only one functional change.
* [x] I have updated all required description fields above.
* [x] My PR adheres to Contributing Guidelines and Documentation.
* [ ] My PR is still work in progress (not ready for review).
* [x] My PR is ready for review and can be safely merged into a codebase.
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