[BUG] [ESP32-S3] Enabling CONFIG_SMP prevents mounting the /data directory at startup using MTD/LittleFS

[engdavidiogo]

Description / Steps to reproduce the issue

Description

I noticed a recent issue on ESP32-S3 board configurations related to Wi-Fi (STA/AP): the default esp32s3-devkit:sta_softap configuration does not enable SMP.

When CONFIG_SMP is enabled, board bringup fails during SPI flash storage initialization, and /data (mounted from MTD as non-volatile storage) is not created.

The bringup consistently fails in the flash filesystem setup path.

Base configuration used

./tools/configure.sh esp32s3-devkit:sta_softap

Then SMP was enabled (CONFIG_SMP=y).

Steps to reproduce

1. Configure with:

   ./tools/configure.sh esp32s3-devkit:sta_softap

2. Enable SMP (CONFIG_SMP=y).
3. Build and flash.
4. Boot and run:

   ls /

5. Try manual mount:

   mount -t littlefs -o forceformat /dev/esp32s3flash /data

Expected behavior

• Bringup completes normally.
• /data is created/mounted from SPI flash MTD.
• Manual mount with forceformat succeeds if media is empty/corrupted.

Actual behavior

• Bringup fails in SPI flash filesystem setup.
• /data is not created.
• Manual mount fails with error 28.

Relevant logs

littlefs: lfs_mount failed ret=-14
nx_mount: ERROR: Bind method failed: -14

littlefs: forceformat requested
lfs_dir_commitcrc: commitcrc mismatch at crc-tag block=0x0 off=0x30 ...
lfs_dir_compact: Superblock 0x0 has become unwritable
littlefs: lfs_format failed ret=-28
nx_mount: ERROR: Bind method failed: -28

ERROR: Failed to setup littlefs
ERROR: Failed to initialize SPI Flash: -28

Notes

• Board: ESP32-S3 DevKit
• Wi-Fi mode: STA + AP
• Reproducible when SMP is enabled
• Without SMP, storage bringup path works as expected

On which OS does this issue occur?

[OS: Linux]

What is the version of your OS?

Ubuntu 24

NuttX Version

release 12.12

Issue Architecture

[Arch: xtensa]

Issue Area

[Area: File System]

Host information

No response

Verification

• I have verified before submitting the report.

[chenglogic]

The lfs_format failure with commitcrc mismatch under CONFIG_SMP=y exposes a fatal cross-core cache collision on the ESP32-S3's eXecute-In-Place (XIP) bus. When Core 0 initiates a physical SPI flash Erase/Write, the flash controller temporarily disables the MMU cache; without a symmetric Inter-Processor Call (IPC) barrier, Core 1 continues fetching instructions from the invalidated XIP memory space, causing bus contention that physically corrupts the LittleFS superblock write stream.

// Architected Fix: nuttx/arch/xtensa/src/esp32s3/esp32s3_spiflash.c
// Strict SMP cross-core halting and cache invalidation before MTD flash transactions.

static void esp32s3_spiflash_oplock(void)
{
#ifdef CONFIG_SMP
  // 1. Force hardware-level pause on the sibling CPU via IPC to prevent XIP fetches
  int sibling_cpu = (this_cpu() == 0) ? 1 : 0;
  up_cpu_pause(sibling_cpu);
#endif
  
  // 2. Safely disable cache for the active CPU accessing the SPI Flash Controller
  cache_hal_disable(CACHE_TYPE_ALL);
}

static void esp32s3_spiflash_opunlock(void)
{
  // 1. Restore MMU cache mapping
  cache_hal_enable(CACHE_TYPE_ALL);
  
#ifdef CONFIG_SMP
  // 2. Release the sibling CPU to resume execution
  int sibling_cpu = (this_cpu() == 0) ? 1 : 0;
  up_cpu_resume(sibling_cpu);
#endif
}

[fdcavalcanti]

Hi @engdavidiogo the default file system for this defconfig is ESP32S3_SPIFLASH_SPIFFS.

To use LittleFS you must enable support for it. Did you do it?
Board Selection → Board common logic → Mount SPI Flash MTD on bring-up

Here is the output on master, which works fine with the default SPIFFS:

nsh> echo "Hi there" > /data/hello.txt
nsh> cat /data/hello.txt
Hi there
nsh> 
nsh> mount
  /data type spiffs
  /proc type procfs
nsh> ls /
/:
 data/
 dev/
 proc/
 var/
nsh> ps
  TID   PID  PPID CPU PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK COMMAND
    0     0     0   0   0 FIFO     Kthread   - Assigned           0000000000000000 0003040 CPU0 IDLE
    1     0     0   1   0 FIFO     Kthread   - Running            0000000000000000 0003032 CPU1 IDLE
    2     0     0 --- 100 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001968 lpwork 0x3fca7020 0x3fca706c
    3     3     0   0 100 RR       Task      - Running            0000000000000000 0003000 nsh_main
    4     0     0 --- 255 RR       Kthread   - Waiting  Semaphore 0000000000000000 0000688 spiflash_op 0x3fcadb5c
    5     0     0 --- 255 RR       Kthread   - Waiting  Semaphore 0000000000000000 0000688 spiflash_op 0x3fcadb5c
    6     0     0 --- 223 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001984 rt_timer
    7     0     0 --- 253 RR       Kthread   - Waiting  MQ empty  0000000000000000 0006600 wifi
    8     0     0 --- 100 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001968 netdev-wlan0 0x3fcb8028 0
nsh> 

Output using littlefs:

nsh> mount
  /data type littlefs
  /proc type procfs
nsh> echo "Hello littlefs" > /data/hello.txt
nsh> cat /data/hello.txt
Hello littlefs
nsh> 
nsh> ps
  TID   PID  PPID CPU PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK COMMAND
    0     0     0   0   0 FIFO     Kthread   - Assigned           0000000000000000 0003040 CPU0 IDLE
    1     0     0   1   0 FIFO     Kthread   - Running            0000000000000000 0003032 CPU1 IDLE
    2     0     0 --- 100 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001968 lpwork 0x3fca7130 0x3fca717c
    3     3     0   0 100 RR       Task      - Running            0000000000000000 0003000 nsh_main
    4     0     0 --- 255 RR       Kthread   - Waiting  Semaphore 0000000000000000 0000688 spiflash_op 0x3fcadd9c
    5     0     0 --- 255 RR       Kthread   - Waiting  Semaphore 0000000000000000 0000688 spiflash_op 0x3fcadd9c
    6     0     0 --- 223 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001984 rt_timer
    7     0     0 --- 253 RR       Kthread   - Waiting  MQ empty  0000000000000000 0006600 wifi
    8     0     0 --- 100 RR       Kthread   - Waiting  Semaphore 0000000000000000 0001968 netdev-wlan0 0x3fcb7c48 0
nsh> 

[engdavidiogo]

Thank you for the feedback, @fdcavalcanti.

Regarding your question about enabling LittleFS support:

Yes, I have enabled LittleFS support and, when CONFIG_SMP is disabled, the behavior is correct —/data is mounted normally during bringup.

However, the issue appears when CONFIG_SMP is enabled in this context.

Enabling dual-core support on the ESP32-S3 (CONFIG_SMP=y) causes the bringup process to fail while attempting to mount the /data directory.

[fdcavalcanti]

If you look at the ps output I added, you will see both cores available, which means SMP is on.

Steps to reproduce:

$ ntxbuild start esp32s3-devkit sta_softap --apps-dir apps
$ ntxbuild kconfig --enable CONFIG_SMP
$ ntxbuild kconfig --enable CONFIG_ESP32S3_SPIFLASH_LITTLEFS
$ ntxbuild build -j10

Tested on NuttX e2f3950d45946eb765dd5fab13a67b7bc70b8a51 and apps e4b84b29d47b98a666df524d6f2d38904c972de5.

Could you erase your entire flash and try again?
Use this to erase:

$ esptool.py erase_flash

Then flash. If you had a different file system before using Little FS, it could cause this issue.

[fdcavalcanti]

Hi @engdavidiogo did you solve the problem?

[engdavidiogo]

Hi @fdcavalcanti
Thank you again for your reply, and sorry for the delay in getting back to you!

I am not exactly sure what may have happened earlier, but everything seems to be working correctly now

My guess is that there may have been some issue during the checkout of version 12.12, since esptool.py erase_flash was used during my tests

As I am no longer able to reproduce the behavior, I am closing this issue