Albert ARIBAUD wrote:
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.
The new hose pointer is passed into that function - the calling code would have to either malloc that, or use a static struct (as it is done on IXP, because there is only one PCI bus). Both will fail before relocation - the hose structure would have to be embedded into the global data struct.
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?
I don't see a reason to do that - my vote would be to do the PCI initialization after relocation, but I am not sure if there are any ARM boards that need this for whatever reason. If there are any, I would expect them to be broken anyway since relocation was added, but I can't be sure.
cu Michael