Messages in this thread Patch in this message | | | Subject | Re: [PATCH] PCI fixes for 2.6.9 | Date | Tue, 19 Oct 2004 15:42:19 -0700 | From | Greg KH <> |
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ChangeSet 1.1997.37.57, 2004/10/06 13:53:18-07:00, johnrose@austin.ibm.com
[PATCH] PCI Hotplug: RPA DLPAR - remove error check
Here's a really long explanation for a really short patch! :)
As an unfortunate side effect of runtime addition/removal of PCI Host Bridges, the RPA DLPAR driver can no longer depend on the success of ioremap_explicit() (and therefore remap_page_range()) for the case of DLPAR adding an I/O Slot.
Without addressing this, an attempt to add the first child slot of a newly added PHB will fail when __ioremap_explicit() determines the mappings for that range to already exist.
For a little context, __ioremap_explicit() creates mappings for the range of a newly added slot. Here's why these calls will be expected to fail in some cases. Keep in mind that at boot-time, the PPC64 kernel calls ioremap() for the entire range spanned by each PHB. Consider the following scenarios of DLPAR-adding an I/O slot.
1) Just after boot, one removes an I/O slot. At this point the range associated with the parent PHB is fragmented, and the child range for the slot in question is iounmap()'ed. One then re-adds the slot, at which point remap_page_range()/ioremap_explicit() restores the mappings that were previously removed.
2) One adds a new PHB, at which point the ppc64-specific addition ioremaps the entire PHB range. One then performs a DLPAR-add of a child slot of that PHB. At this point, mappings already exist for the range of the slot to be added. So remap_page_range()/ioremap_explicit() will fail at this point.
The problem is, there's not a good way to distinguish between cases 1 and 2 from the perspective of the DLPAR driver. Because of that, I believe the correct solution to be:
- Removal of relevant error prints from iounmap_explicit(), which is only used for DLPAR. - Removal of error code checks from the RPA driver
Signed-off-by: John Rose <johnrose@austin.ibm.com> Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
drivers/pci/hotplug/rpadlpar_core.c | 8 ++------ 1 files changed, 2 insertions(+), 6 deletions(-)
diff -Nru a/drivers/pci/hotplug/rpadlpar_core.c b/drivers/pci/hotplug/rpadlpar_core.c --- a/drivers/pci/hotplug/rpadlpar_core.c 2004-10-19 15:22:29 -07:00 +++ b/drivers/pci/hotplug/rpadlpar_core.c 2004-10-19 15:22:29 -07:00 @@ -158,12 +158,8 @@ dn->bussubno = child->number; - /* ioremap() for child bus */ - if (remap_bus_range(child)) { - printk(KERN_ERR "%s: could not ioremap() child bus\n", - __FUNCTION__); - return 1; - } + /* ioremap() for child bus, which may or may not succeed */ + remap_bus_range(child); return 0; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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