Merge branch 'mxc-pu-imxfb' of git://pasiphae.extern.pengutronix.de/git/imx/linux...

[linux-2.6-omap-h63xx.git] / arch / arm / mach-footbridge / include / mach / memory.h

diff --git a/arch/arm/mach-footbridge/include/mach/memory.h b/arch/arm/mach-footbridge/include/mach/memory.h
index 6ae2f1a07ab90b585e122ee8596cbd4f3f7b4b6a..cb16e59d87b63c81f807b67c65b013fa7c11e763 100644 (file)
--- a/arch/arm/mach-footbridge/include/mach/memory.h
+++ b/arch/arm/mach-footbridge/include/mach/memory.h
@@ -30,9 +30,18 @@
 extern unsigned long __virt_to_bus(unsigned long);
 extern unsigned long __bus_to_virt(unsigned long);
 #endif
+#define __virt_to_bus  __virt_to_bus
+#define __bus_to_virt  __bus_to_virt
 
 #elif defined(CONFIG_FOOTBRIDGE_HOST)
 
+/*
+ * The footbridge is programmed to expose the system RAM at the corresponding
+ * address.  So, if PAGE_OFFSET is 0xc0000000, RAM appears at 0xe0000000.
+ * If 0x80000000, then its exposed at 0xa0000000 on the bus. etc.
+ * The only requirement is that the RAM isn't placed at bus address 0 which
+ * would clash with VGA cards.
+ */
 #define __virt_to_bus(x)       ((x) - 0xe0000000)
 #define __bus_to_virt(x)       ((x) + 0xe0000000)