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

Marek Vasut
2013-05-21T10:54:59Z

Dear Sergey Yanovich,

> Dear Marek Vasut,
>
> On Tue, 2013-05-21 at 12:39 +0200, Marek Vasut wrote:
> > > 2.2.5.2 of Marvell PXA27x Processor Family Developers Manual says:
> > > "The PXA27x processor cache configuration is identical to that of
> > > the PXA255 processor."
> > >
> > > As a result, it is perfectly legitimate to use PXA25X
> > > 'lock_cache_for_stack' on PXA27X as well.
> >
> > Why would you need this on PXA27x ? Is SRAM not enough?
>
> SRAM is battery-backup.

SRAM is just the in-CPU bit of fast RAM. What do you mean by "battery-backup" ?

> It can be used as a ultra-fast persistent
> storage in OS. Wasting a quater of it just to boot the system isn't the
> best choice.

The SRAM is used for stack in U-Boot until you leave board_init_f, then the
stack is relocated to DRAM. The OS can use SRAM as needed, U-Boot is no longer
operational once you load subsequent OS. What's the problem?

Best regards,
Marek Vasut