[U-Boot] calling pci_init before relocation?

[Albert ARIBAUD]

Le 30/01/2011 23:46, Michael Schwingen a écrit :
> 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.

Tough luck -- BTW, how does this code allocate the memory? The heap is 
obviously not going to work before relocation.

>> 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.

Hmm... Now let's reverse the question: why should PCI be initialized 
before relocation? At this point the only goal of the init_board_f code 
is to get the RAM working for relocation, and the only useful device is 
the serial console. Does pci_init() help for either RAM or console?

> cu
> Michael

Amicalement,
-- 
Albert.