powerpc/44x: Support 16K/64K base page sizes on 44x

This adds support for 16k and 64k page sizes on PowerPC 44x processors.

The PGDIR table is much smaller than a page when using 16k or 64k
pages (512 and 32 bytes respectively) so we allocate the PGDIR with
kzalloc() instead of __get_free_pages().

One PTE table covers rather a large memory area when using 16k or 64k
pages (32MB or 512MB respectively), so we can easily put FIXMAP and
PKMAP in the area covered by one PTE table.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Vladimir Panfilov <pvr@emcraft.com>
Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 44 insertions, 14 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f7f5448..1af2257 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -405,23 +405,53 @@ config PPC_HAS_HASH_64K
 	depends on PPC64
 	default n
 
-config PPC_64K_PAGES
-	bool "64k page size"
-	depends on PPC64
-	select PPC_HAS_HASH_64K
+choice
+	prompt "Page size"
+	default PPC_4K_PAGES
 	help
-	  This option changes the kernel logical page size to 64k. On machines
-	  without processor support for 64k pages, the kernel will simulate
-	  them by loading each individual 4k page on demand transparently,
-	  while on hardware with such support, it will be used to map
-	  normal application pages.
+	  Select the kernel logical page size. Increasing the page size
+	  will reduce software overhead at each page boundary, allow
+	  hardware prefetch mechanisms to be more effective, and allow
+	  larger dma transfers increasing IO efficiency and reducing
+	  overhead. However the utilization of memory will increase.
+	  For example, each cached file will using a multiple of the
+	  page size to hold its contents and the difference between the
+	  end of file and the end of page is wasted.
+
+	  Some dedicated systems, such as software raid serving with
+	  accelerated calculations, have shown significant increases.
+
+	  If you configure a 64 bit kernel for 64k pages but the
+	  processor does not support them, then the kernel will simulate
+	  them with 4k pages, loading them on demand, but with the
+	  reduced software overhead and larger internal fragmentation.
+	  For the 32 bit kernel, a large page option will not be offered
+	  unless it is supported by the configured processor.
+
+	  If unsure, choose 4K_PAGES.
+
+config PPC_4K_PAGES
+	bool "4k page size"
+
+config PPC_16K_PAGES
+	bool "16k page size" if 44x
+
+config PPC_64K_PAGES
+	bool "64k page size" if 44x || PPC_STD_MMU_64
+	select PPC_HAS_HASH_64K if PPC_STD_MMU_64
+
+endchoice
 
 config FORCE_MAX_ZONEORDER
 	int "Maximum zone order"
-	range 9 64 if PPC_64K_PAGES
-	default "9" if PPC_64K_PAGES
-	range 13 64 if PPC64 && !PPC_64K_PAGES
-	default "13" if PPC64 && !PPC_64K_PAGES
+	range 9 64 if PPC_STD_MMU_64 && PPC_64K_PAGES
+	default "9" if PPC_STD_MMU_64 && PPC_64K_PAGES
+	range 13 64 if PPC_STD_MMU_64 && !PPC_64K_PAGES
+	default "13" if PPC_STD_MMU_64 && !PPC_64K_PAGES
+	range 9 64 if PPC_STD_MMU_32 && PPC_16K_PAGES
+	default "9" if PPC_STD_MMU_32 && PPC_16K_PAGES
+	range 7 64 if PPC_STD_MMU_32 && PPC_64K_PAGES
+	default "7" if PPC_STD_MMU_32 && PPC_64K_PAGES
 	range 11 64
 	default "11"
 	help
@@ -441,7 +471,7 @@ config FORCE_MAX_ZONEORDER
 
 config PPC_SUBPAGE_PROT
 	bool "Support setting protections for 4k subpages"
-	depends on PPC_64K_PAGES
+	depends on PPC_STD_MMU_64 && PPC_64K_PAGES
 	help
 	  This option adds support for a system call to allow user programs
 	  to set access permissions (read/write, readonly, or no access)