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feature: allow flashing of uf2s with non-contiguous blocks #23

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feature: allow flashing of uf2s with non-contiguous blocks #23

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55786ed
feature: allowflashing of uf2s with non-contiguous blocks
cathiele Feb 27, 2026
543fba4
Improve alignment handling in FLASH_ERASE
cathiele Mar 3, 2026
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54 changes: 37 additions & 17 deletions ui/uf2.c
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Original file line number Diff line number Diff line change
Expand Up @@ -25,12 +25,12 @@ uintptr_t prog_area_end;
typedef struct
{
const char* filename;
uint32_t prog_addr;
uint32_t num_blks;
uint32_t num_blks_read;
uint32_t num_blks_written;
uint32_t family_id;
bool malformed_uf2; // indicates a badly formed pico2 uf2
uint8_t erased_sectors[512]; // covers up to 16MB of flash (4096 sectors × 4KB)
} prog_state_t;

static struct uf2_block _block_buf __attribute((aligned(256)));
Expand Down Expand Up @@ -71,7 +71,9 @@ bool handle_boot_stage2(const struct uf2_block* b)
uint8_t boot2[BOOT2_SIZE];
memcpy(boot2, (void*)XIP_BASE, BOOT2_SIZE);

FLASH_ERASE(XIP_BASE, b->num_blocks * b->payload_size);
// Only erase sector 0; all other sectors are erased on demand via ensure_sector_erased()
FLASH_ERASE(XIP_BASE, FLASH_SECTOR_SIZE);
s.erased_sectors[0] |= 1; // mark sector 0 as erased in the bitmap
FLASH_PROG(XIP_BASE, boot2, BOOT2_SIZE);

if (b->target_addr != XIP_BASE)
Expand All @@ -98,8 +100,8 @@ static inline int FLASH_ERASE(uintptr_t address, uint32_t size_bytes)
(CFLASH_SECLEVEL_VALUE_SECURE << CFLASH_SECLEVEL_LSB) |
(CFLASH_ASPACE_VALUE_RUNTIME << CFLASH_ASPACE_LSB)};

// Round up size_bytes or rom_flash_op will throw an alignment error
uint32_t size_aligned = (size_bytes + 0x1FFF) & -FLASH_SECTOR_SIZE;
// Round up size_bytes to the next sector boundary
uint32_t size_aligned = (size_bytes + FLASH_SECTOR_SIZE - 1) & -FLASH_SECTOR_SIZE;

return rom_flash_op(cflash_flags, address, size_aligned, NULL);
}
Expand All @@ -118,6 +120,30 @@ bool handle_boot_stage2(const struct uf2_block* b) { return false; }

#endif

// Erase the sector containing 'address', if not already erased.
// Uses a bitmap in prog_state_t to avoid erasing the same sector twice.
static int ensure_sector_erased(uintptr_t address)
{
uintptr_t sector_base = address & ~((uintptr_t)(FLASH_SECTOR_SIZE - 1));
uint32_t sector_idx = (sector_base - XIP_BASE) / FLASH_SECTOR_SIZE;
if (sector_idx >= sizeof(s.erased_sectors) * 8)
{
DEBUG_PRINT("Sector index %d out of bitmap range\n", sector_idx);
return -1;
}

uint32_t byte_idx = sector_idx / 8;
uint8_t bit_mask = 1u << (sector_idx % 8);

if (s.erased_sectors[byte_idx] & bit_mask)
return 0; // already erased

int ret = FLASH_ERASE(sector_base, FLASH_SECTOR_SIZE);
if (ret >= 0)
s.erased_sectors[byte_idx] |= bit_mask;
return ret;
}

char* get_short_path(const char* path)
{
static char sfn_path[512];
Expand Down Expand Up @@ -210,6 +236,12 @@ enum uf2_result_e __attribute__((optimize("-O0"))) load_application_from_uf2(con
// if block contains proginfo area, set it to all 0xFF's
bl_proginfo_clear(b->data, b->target_addr, b->payload_size);

if (ensure_sector_erased(b->target_addr) < 0)
{
DEBUG_PRINT("Erase failed for block %d at address 0x%08x\n", b->block_no, b->target_addr);
return UF2_UNKNOWN;
}

FLASH_PROG(b->target_addr, b->data, FLASH_PAGE_SIZE);

s.num_blks_written++;
Expand All @@ -224,10 +256,9 @@ enum uf2_result_e __attribute__((optimize("-O0"))) load_application_from_uf2(con
continue;
}

text_directory_ui_set_status("Erasing flash...");
if (!handle_boot_stage2(b))
{
if (FLASH_ERASE(b->target_addr, s.num_blks * b->payload_size) < 0)
if (ensure_sector_erased(b->target_addr) < 0)
{
// Don't even attempt to program if the erase fails
return UF2_UNKNOWN;
Expand All @@ -236,7 +267,6 @@ enum uf2_result_e __attribute__((optimize("-O0"))) load_application_from_uf2(con
FLASH_PROG(b->target_addr, b->data, FLASH_PAGE_SIZE);
}

s.prog_addr = b->target_addr;
s.num_blks_written++;
}
}
Expand Down Expand Up @@ -371,12 +401,6 @@ static bool check_1st_block(const struct uf2_block* b)
return false;
}

if (b->target_addr + FLASH_PAGE_SIZE * s.num_blks > prog_area_end)
{
DEBUG_PRINT("Requested range exceeds flash area\n");
return false;
}

return true;
}

Expand All @@ -395,10 +419,6 @@ static bool check_block(const prog_state_t* s, const struct uf2_block* b)
{
return false;
}
if (s->prog_addr + FLASH_PAGE_SIZE * s->num_blks_written != b->target_addr)
{
return false;
}

return true;
}