[U-Boot] [PATCH] arm: pxa: PXA270 D-Cache as ram

Marek Vasut
2013-05-21T19:02:29Z

Dear Sergey Yanovich,

> On Tue, 2013-05-21 at 17:00 +0200, Marek Vasut wrote:
> > > Yes, the patch as it is will only affects relocation speed and preserve
> > > SRAM from corruption.
> >
> > Now this is the right (convincing) argument! What kind of corruption ?
> > When does it occur ?
>
> The whole 256 kB of SRAM could be used for persistent storage with the
> patch. Without it, part of SRAM should be dedicated for U-Boot stack or
> be overwritten on boot.

This won't hold on any PXA that uses SPL, like the vpac270 with OneNAND SPL and
PXA3xx (which is out of tree, none of your concern ;-) )

> > > The speed gain can also be applied to uImage
> > > copying/unpacking, but that requires deeper understanding than I have
> > > at the moment.
> >
> > Uh ... I lost you here. Can you please elaborate some more ?
>
> You are right. After SDRAM is configured, it is enough to turn on data
> caching to receive its speed benefits.

You must make sure anything that uses DMA won't crash. But I don't understand
how locking cachelines as RAM and enabling dcache relate to each other in this
context.

Best regards,
Marek Vasut