Nick Thompson wrote:
On 01/12/09 10:13, Nick Thompson wrote:
On 01/12/09 00:55, Scott Wood wrote:
This change will break drivers that support large page and use the default read_page functions, but do not implement cmd_ctrl (they replace cmdfunc instead). This includes fsl_elbc_nand, mxc_nand, and mpc5121_nfc. While I'd like to move them to implementing their own read_page-type functions instead of cmdfunc, is there any way to make it a smoother transition?
Yes, as it stands they would need modifying simultaneously and I have no way to test such a change myself. The only required change in cmdfunc is not to wait after a read0 request. You maybe in a better position to decide if this has wider repercussions, but I will take a look at the above drivers as well. [This is the main reason I made this an RFC].
How about, if nand_wait_cache_load was replaceable (by a no-op in your case)
Or it could be off by default, and enabled only on those platforms where it works and is beneficial.
and the pre-fetch optimisation could be disabled by setting rstate to (INIT | NO_REQ) on every page read function call #ifdef CONFIG_NAND_NO_PREFETCH_READS?
This leaves a problem with NAND_CMD_RNDOUT which is used by oob_first page reads but not supported by fsl_elbc_cmdfunc. I expect you don't use oob_first though..?
Right. It's also used on swecc, but we don't use that either.
I believe this would allow you to restore the original sequences and keep you going until you can define your own page read functions.
[BTW these changes applied quite cleanly to my Linux tree and give similar performance gains there as well. If we can reach agreement here, I will make patches for Linux as well. Unfortunately, my tree is 2.6.18 with backported NAND support from 2.6.32rc1, but I can deal with that.]
If possible, it would be nice to run these patches by the Linux list now, so we get their feedback earlier rather than later.
-Scott