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@denx.de If God had a beard, he'd be a UNIX programmer.
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