Re: flash read performance

Jamie Lokier
2008-11-07T05:57:14Z

Trent Piepho wrote:
> On Fri, 7 Nov 2008, Jamie Lokier wrote:
> > Based on Andre's observation, I will soon try enabling cache for my
> > NOR, and see if it makes a difference to cold-cache read performance.
> > I don't expect it, but it's worth a try.
>
> It possible it could help by efficiently doing the reads back-to-back with
> no wasted cycles between them. I think it's necessary if you want to
> benefit from page mode, but that's something I haven't tried yet.
>
> > You might also find the write operation to be unreliable, if the
> > caching mode is write-back rather than write-through.
>
> Proper use of "sync" instructions, or whatever the arch uses to insure that
> writel() is strictly ordered should fix that.

I think that won't work because strongly ordered writes don't
translate directly to bus transactions when the region is mapped with
ioremap_cached(). The flash wants exact bus transactions.

-- Jamie