On 3 Apr 2015, stefan@agner.ch wrote:
I will remove the page read on NAND_CMD_SEQIN, since we memcpy the full page anyway. I also just realized that the page read actually happens always and hence slows down even full page writes...
Yes, I remove this in Linux (4.0) and it corrupted things when writing. I think your previous conclusion about we never use 'write caching' was wrong.
This one is for writes,
case NAND_CMD_SEQIN: /* Pre-read for partial writes. */
This one is for reads,
case NAND_CMD_READ0:
The interface between 'nand_base' and the MTD driver is hard to decipher. Does Scott (or anyone) know if there is any documentation on this?
Stefan is completely correct that if a full page is being written, then the 'SEQIN' should not read a page. However, I only see 'column' being passed. How is 'SEQIN' and 'PAGEPROG' to detect if a full page is being written or not?
The other way to handle things would to be to investigate the NFC_CFG[PAGE_CNT] and NFC_SECSZ to have the virtual pages support sub-pages. I think the OOB mapping would be non-standard in such cases. The buffer management in the driver is most simple in it's current form. The other versions that I found seemed to be buggy to me. However, the current driver doesn't use all of the NFC SRAM buffer space.
Btw, the READ_OOB is very nice for Linux as well. It is a much faster mount of UBI/UbiFs as well.
Fwiw, Bill Pringlemeir.