[PATCH] PPC64 remove __ioremap_explicit() error message

This patch, from John Rose, is the counterpart of one recently
forwarded by Greg KH.  It has the same description, but isn't the same
patch - this is the arch/ppc64 part of the change.

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

Here's the first of these.

Signed-off-by: John Rose <johnrose@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/ppc64/mm/init.c b/arch/ppc64/mm/init.c
index cf0c57a7d2e1d52c19f76f884bcd8a5c29a1f3c9..74f517f6b5f0bf7b74a461e7a4153c20959a7280 100644 (file)
--- a/arch/ppc64/mm/init.c
+++ b/arch/ppc64/mm/init.c
@@ -265,7 +265,7 @@ int __ioremap_explicit(unsigned long pa, unsigned long ea,
        } else {
                area = im_get_area(ea, size, IM_REGION_UNUSED|IM_REGION_SUBSET);
                if (area == NULL) {
-                       printk(KERN_ERR "could not obtain imalloc area for ea 0x%lx\n", ea);
+                       /* Expected when PHB-dlpar is in play */
                        return 1;
                }
                if (ea != (unsigned long) area->addr) {