tmedicci opened a new pull request, #18874:
URL: https://github.com/apache/nuttx/pull/18874
## Summary
* [arch|board]/risc-v: Allow BSS segments on PSRAM for ESP32-P4
* Enables moving BSS data segments to the external PSRAM on ESP32-P4. This
is controlled by a Kconfig option.
## Impact
Impact on user: No.
Impact on build: Yes. Allows .bss specific segments to the external PSRAM.
Impact on hardware: No.
Impact on documentation: No.
Impact on security: No.
Impact on compatibility: No.
## Testing
We need to force a specific segment to check if it's being properly moved to
the external PSRAM. `ext_ram.bss.*` segments are located at the external PSRAM.
To test it, it's possible to enable the `FS_HEAPSIZE` and set
`FS_HEAPBUF_SECTION=".ext_ram.bss.buf"`. Considering the
`esp32p4-function-ev-board:psram_usrheap` defconfig as a starting point:
### Building
```
make -j distclean
./tools/configure.sh -S esp32p4-function-ev-board:psram_usrheap
kconfig-tweak -e ESPRESSIF_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY
kconfig-tweak -e FS_TMPFS
kconfig-tweak --set-val FS_HEAPSIZE 2097152
kconfig-tweak --set-str FS_HEAPBUF_SECTION ".ext_ram.bss.buf"
make olddefconfig
make flash ESPTOOL_PORT=/dev/ttyACM0
picocom -b 115200 /dev/ttyUSB1
```
### Running
Check `free` to ensure that the fs_heap has 2MiB and user heap is less than
the expected 32MiB - 2MiB (the difference is now part of the fs heap).
Also, check NuttX's `nuttx.map` to check if `.ext_ram.bss.buf` is properly
assigned to the external RAM.
### Results
#### `free`
```
nsh> free
total used free maxused maxfree nused nfree name
2097148 1564 2095584 1944 2095584 17 1 heapfs
601860 5452 596408 8088 594152 24 2 Kmem
31457276 4276 31453000 4656 31453000 8 1 Umem
```
#### `nuttx.map`
```
.ext_ram.bss 0x48000000 0x200000
0x48000000 _ext_ram_bss_start =
ABSOLUTE (.)
*(.ext_ram.bss .ext_ram.bss.*)
.ext_ram.bss.buf
0x48000000 0x200000
/home/tiago/Documents/work/espressif/projects/nuttx/nuttxspace/nuttx/staging/libfs.a(fs_heap.o)
0x48200000 . = ALIGN (0x4)
0x48200000 _ext_ram_bss_end =
ABSOLUTE (.)
```
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