[U-Boot-Users] start.S for mpc85xx and debug via BDI2000

[U-Boot-Users] start.S for mpc85xx and debug via BDI2000

[Armand Ciejak]

I'm having problem in debugging U-boot for a MPC8540 processor.
I'm debugging the very first instructions with the BDI2000. The system 
crash at 2 places in start.S:

1- when clearing debug registers
2- when setting up interrupt vectors

	/* clear registers */
	li	r0,0
	mtspr	SRR0,r0
	mtspr	SRR1,r0
	mtspr	CSRR0,r0
	mtspr	CSRR1,r0
	mtspr	MCSRR0,r0
	mtspr	MCSRR1,r0

	mtspr	ESR,r0
	mtspr	MCSR,r0
	mtspr	DEAR,r0

HERE ->	mtspr	DBCR0,r0
	mtspr	DBCR1,r0
	mtspr	DBCR2,r0
	mtspr	IAC1,r0
	mtspr	IAC2,r0
	mtspr	DAC1,r0
	mtspr	DAC2,r0

	mfspr	r1,DBSR
	mtspr	DBSR,r1		/* Clear all valid bits */

	mtspr	PID0,r0
	mtspr	PID1,r0
	mtspr	PID2,r0
	mtspr	TCR,r0

	mtspr	BUCSR,r0	/* disable branch prediction */
	mtspr   MAS4,r0
	mtspr   MAS6,r0
	isync

	/* Setup interrupt vectors */
HERE ->	lis     r1,0xfff8
	mtspr IVPR, r1

	li      r1,0x0100
	mtspr	IVOR0,r1	/* 0: Critical input */
	li      r1,0x0200
	mtspr	IVOR1,r1	/* 1: Machine check */
	li      r1,0x0300
	mtspr	IVOR2,r1	/* 2: Data storage */
	li      r1,0x0400
	mtspr	IVOR3,r1	/* 3: Instruction storage */
	li	r1,0x0500
	mtspr	IVOR4,r1	/* 4: External interrupt */
	li	r1,0x0600
	mtspr	IVOR5,r1	/* 5: Alignment */
	li	r1,0x0700
	mtspr	IVOR6,r1	/* 6: Program check */
	li	r1,0x0800
	mtspr	IVOR7,r1	/* 7: floating point unavailable */
	li	r1,0x0c00
	mtspr	IVOR8,r1	/* 8: System call */
	/* 9: Auxiliary processor unavailable(unsupported) */
	li	r1,0x1000
	mtspr	IVOR10,r1	/* 10: Decrementer */
	li	r1,0x1400
	mtspr	IVOR13,r1	/* 13: Data TLB error */
	li	r1,0x1300
	mtspr	IVOR14,r1	/* 14: Instruction TLB error */
	li	r1,0x2000
	mtspr	IVOR15,r1	/* 15: Debug */

What should I do to be able to debug this part?

[U-Boot-Users] start.S for mpc85xx and debug via BDI2000

[Kylo Ginsberg]

On 5/25/05, Armand Ciejak <armand.ciejak@free.fr> wrote:
> I'm having problem in debugging U-boot for a MPC8540 processor.
> I'm debugging the very first instructions with the BDI2000. The system
> crash at 2 places in start.S:
> 
> 1- when clearing debug registers
> 2- when setting up interrupt vectors

I'm assuming you mean "the system crashes if I set a breakpoint at
...".  The 85xx is a real pain in this regard, because it wants to
fetch andexecute the debug exception vector first thing, so BDM
debugging only works if the debug exception is enabled and its vector
is fetchable.  So the two points you list below: 1) disable debug
exceptions 2) overwrite the base address for exceptions.

I just work around this by using TI to step through this very early code.

Also, btw, you'll encounter a similar problem when debugging early
linux startup b/c u-boot doesn't currently relocate exception vectors
to ram.  I posted a u-boot patch for this issue a month or so back;
you might want to google for that.

Cheers,
Kylo