From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Schwingen Date: Mon, 31 Jan 2011 10:45:26 +0100 Subject: [U-Boot] calling pci_init before relocation? In-Reply-To: <4D45EDC4.9020605@free.fr> References: <4D45DA9F.5000903@discworld.dascon.de> <4D45E10D.4020302@free.fr> <4D45EA43.3070108@discworld.dascon.de> <4D45EDC4.9020605@free.fr> Message-ID: <4D4684B6.3040407@discworld.dascon.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Albert ARIBAUD wrote: > Le 30/01/2011 23:46, Michael Schwingen a ?crit : >> Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD: >>> Hi Michael, >>> >>> Le 30/01/2011 22:39, Michael Schwingen a ?crit : >>>> 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