Comparing the Samsung K9F1G08U0D (2048 + 64 page size) datasheet with that of
K9F1G08U0C (512 + 16 page size), you can realize the significant difference of
spare data handling.
- For the 2048 page size NAND flash, the spare area is selected by the highest
column address.
- For the 512 page size NAND, there's no such a bit in the address sequence,
but the spare area can be read by the `NAND_CMD_READOOB` command. The page
program command supports loading 512 + 16 bytes at once, writing the page data
with OOB, this means the OOB (spare area) cannot be handled alone here.
This probably means this operation cannot be supported for 512 page size
devices, and we need something like this to be added in `nand_page_command`,
`flash/nand/core.c`:
```c
if (oob_only && NAND_CMD_SEQIN == cmd && nand->page_size <= 512) {
LOG_ERROR("writing with oob_only option is not supported for
NAND flashes with 512 byte pagesize");
return ERROR_NAND_OPERATION_FAILED;
}
```
Still, I might need to figure out why the first block at the specific write
offset is damaged in a K9F1G08U0C chip: some garbage data is written into the
main area of the first page as well as the spare area, so it's marked bad
because of the garbage data in the spare area; the erasure operation returned
status 0xC1 which means a failure according to the chip datasheet. Before this
failure, I have erased some false bad blocks (produced because of some
misoperation of U-boot `nand write.yaffs` caused by wrong data+oob input
format) successfully.
---
**[tickets:#464] Unexpected behavior of writing 512 page size NAND with
`oob_only` mode**
**Status:** new
**Milestone:** 0.12.0
**Labels:** nand flash
**Created:** Wed Feb 11, 2026 10:28 PM UTC by wuwbobo2021
**Last Updated:** Wed Feb 11, 2026 10:28 PM UTC
**Owner:** nobody
As far as I know, the `nand write` command is handled by
`handle_nand_write_command` in `flash/nand/tcl.c`, which initializes the input
data structure through `fileio` module and calls `nand_write_page` which calls
`nand_write_page_raw` under raw access mode (currrently the only available mode
for S3C series MPUs), which simply calls `nand_page_command` before
`nand_write_data_page`, and in `nand_page_command` there seems no support for
writing 512 page size NAND with `oob_only` mode, while it supports reading with
`oob_only` mode. But it does something without any warning.
Actually, this has caused a strange problem of damaging the first block at the
specific write offset.
---
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