[U-Boot-Users] 回复: [U-Boot-Users] U-Boot-NG ?

Songmao Tian
2007-07-06T11:53:38Z

what's the trick to use d-cache as memory?

2007/7/3, Wolfgang Denk <wd@denx.de>:
> In message <20070703000910.GA15081@pengutronix.de> you wrote:
> >
> > > You don't? How do you uncompress an image then?
> >
> > On Arm by default zImages are used to generate the uImage, so the kernel
> > decompresses itself.
>
> For the Linux kernel, maybe. But there are many more things than just
> Linux. Think for example about FPGA images, etc.
>
> > > Do you mean you don't relocate the code any more?
> >
> > It still gets copied from the address U-Boot starts (Flash) to RAM, but
> > pointer offsets are not recalculated. This means that you must not use
> > statically initialized pointers during startup since the code is not
> > running at its link address.
>
> Are you doing this for all architectures now?
>
> > The Arm part has done this for years. On PowerPC we have the luxury of
>
> Yes, and this is my major critique to the ARM (and the MIPS, and
> maybe other) ports. We should fix this. Like on PowerPC, U-Boot
> should always be copied to the upper end of RAM instead of a
> precalculated address, as this cannot cope with different RAM sizes.
>
> > having SRAM, so we can setup a stack and do SDRAM initialization in C
> > before jumping to RAM.
>
> Not all PowerPC processors have on-chip or other static RAM; in some
> cases we use (for example) the data cache as memory. Similar
> techniqes should be possible on all architectures.
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
> If God had a beard, he'd be a UNIX programmer.
>
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