Re: XIP aware file system

Nicolas Pitre
2005-02-15T18:05:23Z

On Tue, 15 Feb 2005, David Woodhouse wrote:

> On Tue, 2005-02-15 at 11:38 -0500, Nicolas Pitre wrote:
> > Please study carefully xip_udelay() and try to understand _when_ it is
> > OK to call other functions and when it is not. This function is really
> > where all the magic is happening.
>
> Out of interest, how do we guarantee that there won't be speculative
> prefetching of icache? If you're relying on hardware-specific knowledge
> that it doesn't happen, please document that so that it doesn't bite
> people implementing the XIP primitives on other platforms.

See xip_enable(). You'll find:

(void) map_read(map, adr);
asm volatile (".rep 8; nop; .endr"); /* fill instruction prefetch */

Hopefully that should be suficient to avoid this problem.

Nicolas