ECC in Nand_write_page

[Thomas Gleixner]

On Thursday, 11. July 2002 12:19, Steve Tsai wrote:
> The board I used will display the message, "nand_write_ecc: Failed ECC
> write", so I try to trace the function nand_write_ecc, I found it can
> not write the ECC code into OOB sometime because the ECC in OOB are not
> set as 0xff. There are two conditions to cause the problem, one
> condition is the erase does not success, another condition is that the
> page  was written before. Nand_write_page could write partial page to
> the flash. Does it cause the ECC in OOB was written and ECC can not be
> written next time. For example, nand_write_page write 100 byte the first
> time and if it want to write 412 bytes to the same page next time, it
> will fail. Does anyone have this problem?

Do you use latest CVS code ?
Which filesystem do you use ?
There's only JFFS2, which can handle the nand problem correct.

Read http://www.linux-mtd.infradead.org/tech/nand.html !

1. If an erase fails, the JFFS2 does not use this block.

2. JFFS2 writes only full pages

3. ECC is definitely not written, if you write 100 bytes

	/* Calculate and write the ECC if we have enough data */
	if ((col < mtd->eccsize) && (last >= mtd->eccsize)) {
		nand_calculate_ecc (&this->data_buf[0], &(ecc_code[0]));
		for (i = 0; i < 3; i++)
			this->data_buf[(mtd->oobblock + oob_config.ecc_pos[i])] = ecc_code[i];
		if (oob_config.eccvalid_pos != -1)
			this->data_buf[mtd->oobblock + oob_config.eccvalid_pos] = 0xf0;
	}

	/* Calculate and write the second ECC if we have enough data */
	if ((mtd->oobblock == 512) && (last == mtd->oobblock)) {
		nand_calculate_ecc (&this->data_buf[256], &(ecc_code[3]));
		for (i = 3; i < 6; i++)
			this->data_buf[(mtd->oobblock + oob_config.ecc_pos[i])] = ecc_code[i];
		if (oob_config.eccvalid_pos != -1)
			this->data_buf[mtd->oobblock + oob_config.eccvalid_pos] &= 0x0f;
	}


-- 
Thomas
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