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Re: JFFS2 and XIP
> Another thing. If your processor has a I-cache (and the trend even in
> embedded processors is that they do), your cannot cache the FLASH
> space as it can change underneath the OS (things like sector erases
> are difficult to communicate to the OS). Most folks just run with the
> flash not cached. In that case, running out of FLASH will be
> *significantly* slower than DRAM.
You can cache flash space as long as you have sane cache flush mechanisms
and obviously you go through an uncached mapping when you want to do
anything but read¹.
XIP on a writable flash chip is such a PITA already that the extra hassle
of having to flush the icache and dcache is lost in the noise.
¹ Yes, I know that the i386 can't map the same physical region both cached
² No, I don't care about i386 very much.
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