[U-Boot] SPL broken on i.mx31 platforms

Helmut Raiger
2014-07-08T12:32:20Z

On 07/08/2014 10:05 AM, Helmut Raiger wrote:
>
> I meant, that the SPL is now doing the RAM init and copying of the SPL
> code
> correctly. RAM is working, the SPL code is at 0x87dc0000 after that
> (CRCed it via JTAG).
> I could not track it further (I have very limited development time
> right now ... repeating myself).
>
> After all I need to debug further. If someone could test the current
> state on the
> mx31pdk, this still would be great. Just to rule out any other board
> specific issues.
>
> Helmut

Ok, I've got some new input and I have no clue what's going on.

1) I fixed the first branch to reset (uses b reset instead of ldr pc,
_reset)
2) The startup does:

b reset
...

reset:
- set the cpu to SVC32 mode
- bl cpu_init_crit (cache and MMU stuff, calls low_level_init)
- bl _main

low_level_init:
unlike in mx31pdk this only does:

ldr r0, =ARM_PPMRR /* start from AIPS 2GB region */
mcr p15, 0, r0, c15, c2, 4
mov pc, lr

_main:
- set up stack pointer to internal SRAM
- bl board_init_f

As I can't break right after reset with peedi, I do:

- reset stop
- set pc 0xb8000000
- go -> system never returns

next:
reset stop
- set pc 0xb8000000
- break add hard 0xb80000c8 // set hardware breakpoint to the
'bl board_init_f' instruction
- go
... it stops at the breakpoint
- go
... I'm at the u-boot command prompt

If I set the breakpoint somewhere after the bl board_init_f it fails, if
I break a few instructions
early and go from there it also fails. Tracking down the location
in-between I end up at:

at the end of cpu_init_crit():

mov ip, lr /* persevere link reg across call */
bl lowlevel_init /* go setup pll,mux,memory */
-> mov lr, ip /* restore link */
mov pc, lr /* back to my caller */

That is, if I set the breakpoint to mov lr, ip it works, if I set it one
instruction later it ends working.

Could be struggling with the debugger here, as the SPL probably ran a
few instruction before it
was stopped. Might this be a cache issue? But it is invalidated in
cpu_init_crit() anyway ...

Feeling a little dumbstruck right now ...

Sorry for the mess, but it's hard to describe.

Any ideas?
Helmut

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