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The rp2350 executes in place from external QSPI flash, and a NuttX image normally leaves most of that flash unused. This exposes the unused region as an MTD device so it can carry a filesystem, mirroring what the rp2040 port already provides with rp2040_flash_mtd.c. The region is given by RP23XX_FLASH_MTD_OFFSET and RP23XX_FLASH_MTD_SIZE, both multiples of the 4096 byte erase sector. Initialization fails rather than corrupting the running image if the region would overlap the NuttX binary, checked against __flash_binary_end. Erase and program use the bootrom flash routines. Those stall instruction fetch from the same flash, so they run from SRAM with interrupts disabled and, on SMP builds, the other core parked; afterwards the QSPI interface is returned to execute-in-place mode. By default that restores the fast read mode the bootrom configured at boot; RP23XX_FLASH_MTD_SAFE_XIP instead always uses the bootrom flash_enter_cmd_xip routine, which is slower to execute from but depends only on the documented bootrom entry point. The driver answers BIOC_XIPBASE with the memory-mapped address of the region, so a filesystem supporting execute in place can hand out real flash pointers rather than copying into RAM. The common board bringup registers the device as /dev/rpflash. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com> |
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