[POWERPC] Enable CONFIG_FORCE_MAX_ZONEORDER for all PowerPC, and make selectable

This enables the FORCE_MAX_ZONEORDER Kconfig option for all PowerPC
systems.  Previously, it was enabled only for 64-bit systems.  We also
make the option selectable from the menu, so that the user can specify
different values.  This is useful for 32-bit systems that need to
allocate more than 4MB of physically contiguous memory.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 17 insertions, 6 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f43d82dbc323..625342e1a733 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -211,14 +211,25 @@ source kernel/Kconfig.hz
 source kernel/Kconfig.preempt
 source "fs/Kconfig.binfmt"
 
-# We optimistically allocate largepages from the VM, so make the limit
-# large enough (16MB). This badly named config option is actually
-# max order + 1
 config FORCE_MAX_ZONEORDER
-        int
-        depends on PPC64
+        int "Maximum zone order"
         default "9" if PPC_64K_PAGES
-        default "13"
+        default "13" if PPC64
+        default "11"
+        help
+          The kernel memory allocator divides physically contiguous memory
+          blocks into "zones", where each zone is a power of two number of
+          pages.  This option selects the largest power of two that the kernel
+          keeps in the memory allocator.  If you need to allocate very large
+          blocks of physically contiguous memory, then you may need to
+          increase this value.
+
+          This config option is actually maximum order plus one. For example,
+          a value of 11 means that the largest free memory block is 2^10 pages.
+
+          The page size is not necessarily 4KB.  For example, on 64-bit
+          systems, 64KB pages can be enabled via CONFIG_PPC_64K_PAGES.  Keep
+          this in mind when choosing a value for this option.
 
 config HUGETLB_PAGE_SIZE_VARIABLE
         bool