[U-Boot-Users] PCI stopped working on MPC8343

[Larry Johnson <lrj@acm.org>]

Andre Schwarz wrote:
> Last week 
> my PCI bus has been running fine showing all devices.
> Right now no devices are shown on the bus.
> 
> I'm using CONFIG_83XX_GENERIC_PCI with common setup code for PCI.
> 
> Nothing changed from my side during the last 2 weeks.
> 
> 
> Did I miss any changes in u-boot ?
> 
> 
> regards,
> Andre Schwarz
> Matrix Vision

Hi Andre and everyone,

I was just about to post on I problem I belatedly found with PCI on our
Korat PPC400EPx board.  (I believe the same problem exists on the
Sequoia board, but have not proved it.)  What appears to have broken it
was the following patch (I got to use "git bisect" for the first time):

<patch>
commit 55774b512fdf63c0516d441cc5da7c54bbffb7f2
Author: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Date:   Fri Mar 7 16:04:25 2008 +0900

    pci: Add CONFIG_PCI_SKIP_HOST_BRIDGE config option
    
    In current source code, when the device number of PCI is 0, process PCI
    bridge without fail. However, when the device number is 0, it is not PCI
    always bridge. There are times when device of PCI allocates.
    
    When CONFIG_PCI_SKIP_HOST_BRIDGE is enable, this problem is solved when
    use this patch.
    
    Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
    Acked-by: Stefan Roese <sr@denx.de>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 50ca6b0..7944b66 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -425,6 +425,9 @@ int pci_hose_scan_bus(struct pci_controller *hose, int bus)
 	     dev <  PCI_BDF(bus,PCI_MAX_PCI_DEVICES-1,PCI_MAX_PCI_FUNCTIONS-1);
 	     dev += PCI_BDF(0,0,1))
 	{
+
+	/* Bus 0 is not necessarily PCI bridge. */
+#if defined(CONFIG_PCI_SKIP_HOST_BRIDGE)
 		/* Skip our host bridge */
 		if ( dev == PCI_BDF(hose->first_busno,0,0) ) {
 #if defined(CONFIG_PCI_CONFIG_HOST_BRIDGE)              /* don't skip host bridge */
@@ -434,10 +437,11 @@ int pci_hose_scan_bus(struct pci_controller *hose, int bus)
 			if (getenv("pciconfighost") == NULL) {
 				continue; /* Skip our host bridge */
 			}
-#else
+#else /* CONFIG_PCI_CONFIG_HOST_BRIDGE */
 			continue; /* Skip our host bridge */
-#endif
+#endif /* CONFIG_PCI_CONFIG_HOST_BRIDGE */
 		}
+#endif /* CONFIG_PCI_SKIP_HOST_BRIDGE */
 
 		if (PCI_FUNC(dev) && !found_multi)
 			continue;
@@ -473,8 +477,11 @@ int pci_hose_scan_bus(struct pci_controller *hose, int bus)
 				hose->fixup_irq(hose, dev);
 
 #ifdef CONFIG_PCI_SCAN_SHOW
+#if defined(CONFIG_PCI_SKIP_HOST_BRIDGE)
 			/* Skip our host bridge */
-			if ( dev != PCI_BDF(hose->first_busno,0,0) ) {
+			if ( dev != PCI_BDF(hose->first_busno,0,0) )
+#endif
+			{
 			    unsigned char int_line;
 
 			    pci_hose_read_config_byte(hose, dev, PCI_INTERRUPT_LINE,

</patch>

The patch changes the behavior of the code _unless_
CONFIG_PCI_SKIP_HOST_BRIDGE is defined.  Defining that switch in the
Korat configuration fixes the problem.  The MPC8323ERDB configuration
has also been patched to add the switch, so maybe this is is the cause
of your problem as well.

I was going to submit the patch for Korat, but then decided I'd first
like to ask Nobuhiro and the group whether it might not be better to
change the occurrences of

#if defined(CONFIG_PCI_SKIP_HOST_BRIDGE)

in "drivers/pci/pci.c" to

#if !defined(CONFIG_PCI_NO_SKIP_HOST_BRIDGE)

That would allow those boards that need to patch to specify it
explicity, while leaving the default functionality unchanged.

Comments?

Best regards,
Larry