[PATCH] pxa/vpac270: Enable SparseMEM for 256 MB of RAM

[Marek Vasut]

This patch enables SparseMEM for the Voipac PXA270 board. To work around the
PHYS_OFFSET being set to 0xa0000000 and disallowing us to map the other
partition at 0x80000000, the physical-to-virtual mapping of SDRAM was altered
and the partition at 0x80000000 was moved to 0x10000000 in virtual memory (past
the first SDRAM partition). As the Voipac PXA270 is probably the only PXA270
device which utilizes 256 MB of RAM, adding the following code into memory.h
seems much less painful than tinkering with PHYS_OFFSET.

NOTE: Once the PHYS_OFFSET can be dynamically configured, this code can
probably be removed.

Signed-off-by: Marek Vasut <marek.vasut at gmail.com>
---
 arch/arm/mach-pxa/Kconfig               |    1 +
 arch/arm/mach-pxa/include/mach/memory.h |   21 +++++++++++++++++++++
 arch/arm/mach-pxa/vpac270.c             |    2 ++
 3 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
index 2ff0b32..73d7a0a 100644
--- a/arch/arm/mach-pxa/Kconfig
+++ b/arch/arm/mach-pxa/Kconfig
@@ -264,6 +264,7 @@ config MACH_VPAC270
 	bool "Voipac PXA270"
 	select PXA27x
 	select HAVE_PATA_PLATFORM
+	select ARCH_SPARSEMEM_ENABLE
 	help
 	  PXA270 based Single Board Computer.
 
diff --git a/arch/arm/mach-pxa/include/mach/memory.h b/arch/arm/mach-pxa/include/mach/memory.h
index f626730..705c7a0 100644
--- a/arch/arm/mach-pxa/include/mach/memory.h
+++ b/arch/arm/mach-pxa/include/mach/memory.h
@@ -40,4 +40,25 @@ void cmx2xx_pci_adjust_zones(int node, unsigned long *size,
 #define MAX_DMA_ADDRESS		(PAGE_OFFSET + SZ_64M)
 #endif
 
+/*
+ * Voipac PXA270/PXA270M is probably the only board in the world with PXA27x
+ * that uses more than 128MB or SDRAM (256MB in the 'max configuration'). This
+ * hack should be removed once the PHYS_OFFSET can be configured dynamically.
+ *
+ * The two 128MB SDRAM banks are at addresses 0xa0000000 and 0x80000000. The
+ * following code moves the block of SDRAM at 0x80000000 past the block at
+ * 0xa0000000 in virtual memory and vice versa. We use SparseMEM to map the
+ * pages properly.
+ */
+#ifdef	CONFIG_MACH_VPAC270
+#define	MAX_PHYSMEM_BITS	32
+#define	SECTION_SIZE_BITS	28
+#define	__phys_to_virt(p) \
+	(((p) & 0x0fffffff) | \
+	(((p) & 0x20000000) ? 0 : 0x10000000) | PAGE_OFFSET)
+#define	__virt_to_phys(v) \
+	(((v) & 0x0fffffff) | \
+	(((v) & 0x10000000) ? 0x80000000 : 0xa0000000))
+#endif
+
 #endif
diff --git a/arch/arm/mach-pxa/vpac270.c b/arch/arm/mach-pxa/vpac270.c
index 207a1e5..a2fe43a 100644
--- a/arch/arm/mach-pxa/vpac270.c
+++ b/arch/arm/mach-pxa/vpac270.c
@@ -44,6 +44,8 @@
 #include "generic.h"
 #include "devices.h"
 
+#warning "You have enabled SparseMEM support by selecting a Voipac PXA270 platform. SparseMEM may cause issues with other platforms, so in case you experience such problems, try disabling Voipac PXA270. This applies to kernels that support multiple pxa2xx machines only."
+
 /******************************************************************************
  * Pin configuration
  ******************************************************************************/
-- 
1.7.0