[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD:
> Hi Michael,
>
> Le 30/01/2011 22:39, Michael Schwingen a écrit :
>> Hi,
>>
>> ist it allowed to call pci_init before relocation?
>>
>> The code looks like this is not supposed to happen. However, on ARM,
>> arm_pci_init (which calls pci_init in turn) is called from
>> init_sequence, which happens before relocation.
>>
>> Am I overlooking some way in which this can actually work? Are there
>> boards using this?
>>
>> If I move pci_init down into board_init_r, I can get PCI working on
>> IXP42x, but I am worried if this will cause problems on other boards.
> I cannot see a reason why pci_init should not work before relocation as 
> long as it does not read or write BSS variables or write non-const 
> initialized data -- or overflow the (admittedly limited) C stack.
Because it does just that - from drivers/pci/pci.c:

static struct pci_controller* hose_head;

void pci_init(void)
{
[...]
    hose_head = NULL;

    /* now call board specific pci_init()... */
    pci_init_board();
}

pci_init_board will then call code that ends up calling
pci_register_hose, which adds elements into the list at hose_head.

> Are you asking because you discovered that pci_init does not work when 
> called from board_init_f? If so, did you determine exactly what goes wrong?
The system hangs during early init, and does not get past relocation.

Note that I can only *test* PCI on IXP42x, however, this is common code,
so I do not see how this could behave different on other ARM systems.

If I interpret the code correct, the PCI code is called from
board_init_r on PowerPC platforms.

cu
Michael