MMU Problem bringing up kernel with PPC 603 chip

Bob Beck beck at
Fri Feb 27 08:23:13 EST 2004


I'm bringing up my 1st kernel on a proprietary board
using a PPC 603E chip.

The kernel is configured using the 6xx/7xx ppc selection.

The kernel starts executing at __start in head.S and
branches to early_init(). I have stubbed out the call
to prom_init() since this is an embedded system and
not a power mac (as the comments at the top of the
prom.c file indicate).

The code returns to head.S and branches to mmu_off.
Here is the code for mmu_off.

	addi	r4, r3, __after_mmu_off - _start
	mfmsr	r3
	andi.	r0,r3,MSR_DR|MSR_IR		/* MMU enabled? */
	andc	r3,r3,r0
	mtspr	SRR0,r4
	mtspr	SRR1,r3

This executes all the way to the "RFI" instruction,
but never comes back to the place in the code that
called mmu_off.

Why is the "return from interrupt" going out into
space ? Any suggestions ?

Best Regards,

Bob Beck
beck at

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