On 2010-08-16, Scott Wood scottwood@freescale.com wrote:
On Fri, Aug 13, 2010 at 09:22:21PM +0000, Grant Edwards wrote:
At one point in the legacy NAND code, a distinction was made when reading between completely skipping bad blocks, and filling the buffer with zeroes in place of the bad blocks. It looks like ".jffs2" or ".e" would get you zeroes, and ".jffs2s" or ".i" would get you block skipping.
The zero-fill mode is no longer supported. In 1.3.4, assuming you're not using the legacy NAND code, you need to specify one of ".jffs2", ".e", or ".i" to get block skipping. It doesn't matter which one. In current u-boot these suffixes are accepted and ignored as legacy (bad blocks are always skipped), except for "jffs2s" which apparently never made an appearance outside the legacy code.
OK, that clears up quite a bit of my confusion.
Yes, it's a bit of a mess.
It does appear to be improving. :)
- In the 1.3.4 source code, there are lots of instances where there are boolean flags with names like "jffs2". AFAICT those flags have nothing to do with the JFFS2 filesystem, but simply control whether or not bad flash blocks are skipped during read/write operations. Am I reading the code correctly?
The user interface .jffs2 suffix was to indicate bad block skipping, but opts->jffs2 (which is still around) refers to writing JFFS2 cleanmarkers after erasing a block.
Thanks, that helps.
If in a custom command, I want to read/write a large block of data to/from nand flash while skipping bad blocks what functions do I call? Right now I'm doing something like this:
nand_info[0].read(nand_info+0, offset, sizeof(buffer), &len, buffer)
nand_info[0].write(nand_info+0, offset, bytecount, &len, buffer)
but, I have a feeling that's not right (though it seems to work, I suspect it's not going to skip bad blocks).
You suspect correctly.
In current code there is nand_write_skip_bad() and nand_read_skip_bad() in drivers/mtd/nand/nand_util.c.
Yup, I found those, and the read version is exactly what I need.
I've still got to figure out how to write.
The problem is that the data to be written is streaming. I don't know how much there is, and I don't want to allocate arbitrarily large buffers. So I want to write it one erase-block at a time as it arrives. AFAICT nand_write_skip_bad() can't be used in that situation. Since it provides no indication of how many blocks were skipped, I have no way of knowing where the next block should be written.
I guess that means I need to use the same lower-level API that is being used by nand_write_skip_bad().
In 1.3.4 use nand_read_opts()/nand_write_opts(). Or convince Atmel to support something more recent. :-)
It turns out that Atmel's patches have been merged into the main sources and 2010.6 works fine for the board in question. I don't know why the official Atmel web-page still instructs you to use 1.3.4+patches.