RE: Booting Linux from an ACE File

-----Original Message-----
From: <redacted>

[mailto:linuxppc-embedded-

bounces+stephen=3Dneuendorffer.name@ozlabs.org] On Behalf Of mojtaba
Sent: Friday, May 16, 2008 4:58 AM
To: <redacted>
Subject: Booting Linux from an ACE File
=

Dear all,
=

Could you please explain what happens exactly when Linux is booting

from a

compact flash?

The systemAce file is essentially a script of JTAG commands, some of
which target the FPGA with configuration data and some target the
PowerPC/microblaze with memory write commands.

To my few knowledge, the Linux compressed image will be copied

somewhere in

memory, will be uncompressed and the control will jump to the

beginning

address of the Linux kernel.
=

Is there any boot loader that copies the Linux compressed image to the
memory?

Essentially SystemAce does this for you and jumps to the Linux
bootwrapper code which begins decompressing the kernel.

Where in memory does it put the Linux kernel? For example, if I have 2

DDRs

in my hardware, in which of them it will be put the kernel?

The kernel is compiled at a particular address, typically targetting
whatever memory is low in the system.  I believe the default target
address is 0x40000.  So whatever DDR memory lives at this address will
be targetted.

Can I set the kernel location in memory manually?

If you change how the bootwrapper code and linker script work, yes.

Might be an stupid question but: Is it possible for the kernel to be

half in

BRAMS and half in DDR?

There have been some recent patches on the microblaze mailing lists that
attempt to put some of the latency-critical code (exception handlers and
the like) in BRAM.  Doing this is likely pretty architecture specific,
since you probably have a particular goal in mind.

Steve

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