JFFS2 on 8MB Flash-Chip conneted to MPC850 works extremly slow:(

[David Woodhouse]

krom at dgt-lab.com.pl said:
>  OK, now I'm testing the ocelot's trick. But I do not understand it.

The idea is that read{8,16,32} and write{8,16,32} are used for commands and 
reading status, and should be uncached. copy_from() is used for copying 
data from the flash, and can be cached. We have to flush the cache any 
time a command is sent, because it could be a write or erase command.

This means that we don't get a lot of benefit from storing data in the 
cache for long periods of time (except maybe on read-only flashes), but at 
least we can burst-read to fill a cache line, if the hardware can 
do it.

Flushing the cache on every write cycle to the flash chip may be a little
excessive - perhaps the chip driver itself should have to explicitly flush
the cache when the data are actually likely to change - I'm not sure if
that'd be a win though.

--
dwmw2