[U-Boot] [PATCH] [nand] Implement nand_extent_skip_bad

[Pantelis Antoniou]

Hi Scott,

On Dec 11, 2012, at 12:53 AM, Scott Wood wrote:

> On 12/10/2012 09:24:24 AM, Pantelis Antoniou wrote:
>> When accessing nand any bad blocks encountered are skipped, with no
>> indication about the amount of bad blocks encountered.
>> While this is normally fine, when you have to write a large amount
>> of data in chunks, you need to account for the skipped amount due
>> to the presence of the bad blocks.
>> nand_extend_skip_bad() returns the offset where the next access
>> should occur.
> 
> s/extend/extent/
> 

Yeah.

>> Signed-off-by: Pantelis Antoniou <panto at antoniou-consulting.com>
>> ---
>> drivers/mtd/nand/nand_util.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
>> include/nand.h               |  2 ++
>> 2 files changed, 52 insertions(+)
>> diff --git a/drivers/mtd/nand/nand_util.c b/drivers/mtd/nand/nand_util.c
>> index 2ba0c5e..a25a4cb 100644
>> --- a/drivers/mtd/nand/nand_util.c
>> +++ b/drivers/mtd/nand/nand_util.c
>> @@ -684,6 +684,56 @@ int nand_read_skip_bad(nand_info_t *nand, loff_t offset, size_t *length,
>> 	return 0;
>> }
>> +/**
>> + * nand_extent_skip_bad:
>> + *
>> + * Find the extent of a chunk, return the offset where it ends
>> + * Blocks that are marked bad are skipped and the next block is examined
>> + * instead as long as the extend is short enough to fit even after skipping the
>> + * bad blocks.
>> + *
>> + * @param nand NAND device
>> + * @param offset offset in flash
>> + * @param length extend length
>> + * @return next offset in case of success (loff_t)-1 on error
>> + */
> 
> Would it be better to return this information from existing read/write functions -- either instead of or in addition to exporting this functionality?
> 

Yes it would. However that would require modifying all callers, which would be a hard sell when there's only one user of it.

>> +loff_t nand_extent_skip_bad(nand_info_t *nand, loff_t offset, size_t length)
>> +{
>> +	size_t block_len, block_off;
>> +	loff_t block_start;
>> +
>> +	if ((offset & (nand->writesize - 1)) != 0) {
>> +		printf ("%s: Attempt to check extend non page aligned data\n",
>> +				__func__);
>> +		return (loff_t)-1;
>> +	}
>> +
>> +	while (length > 0) {
>> +
>> +		if (offset >= nand->size) {
>> +			printf("%s: offset >= nand->size (%llx >= %llx)\n",
>> +					__func__, offset, nand->size);
>> +			return (loff_t)-1;
>> +		}
>> +
>> +		block_start = offset & ~(loff_t)(nand->erasesize - 1);
>> +		block_off = offset & (nand->erasesize - 1);
>> +		block_len = nand->erasesize - block_off;
>> +		if (block_len > length)		/* left over */
>> +			block_len = length;
>> +
>> +		if (!nand_block_isbad(nand, block_start))
>> +			length -= block_len;
>> +		else
>> +			debug("%s: bad block at %llx (left %x)\n",
>> +					__func__, block_start, length);
>> +
>> +		offset += block_len;
>> +	}
>> +
>> +	return offset;
>> +}
> 
> This seems duplicative of check_skip_len().
> 

It is. check_skip_len doesn't return the information I need. I could modify check_skip_len with
an extra parameter if that's going to be OK with you.

> -Scott

Regards

-- Pantelis