xtensa: make PLATFORM_DEFAULT_MEM parameters configurable

This allows using xtfpga platform with both MMU and noMMU cores.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -319,6 +319,7 @@ config XTENSA_PLATFORM_S6105
 config XTENSA_PLATFORM_XTFPGA
 	bool "XTFPGA"
 	select ETHOC if ETHERNET
+	select PLATFORM_WANT_DEFAULT_MEM
 	select SERIAL_CONSOLE
 	select XTENSA_CALIBRATE_CCOUNT
 	help
@@ -405,6 +406,41 @@ source "drivers/pcmcia/Kconfig"
 
 source "drivers/pci/hotplug/Kconfig"
 
+config PLATFORM_WANT_DEFAULT_MEM
+	def_bool n
+
+config DEFAULT_MEM_START
+	hex "Physical address of the default memory area start"
+	depends on PLATFORM_WANT_DEFAULT_MEM
+	default 0x00000000 if MMU
+	default 0x40000000 if !MMU
+	help
+	  This is a fallback start address of the default memory area, it is
+	  used when no physical memory size is passed through DTB or through
+	  boot parameter from bootloader.
+
+	  In noMMU configuration the following parameters are derived from it:
+	  - kernel load address;
+	  - kernel entry point address;
+	  - relocatable vectors base address;
+	  - uBoot load address;
+	  - TASK_SIZE.
+
+	  If unsure, leave the default value here.
+
+config DEFAULT_MEM_SIZE
+	hex "Maximal size of the default memory area"
+	depends on PLATFORM_WANT_DEFAULT_MEM
+	default 0x04000000
+	help
+	  This is a fallback size of the default memory area, it is used when
+	  no physical memory size is passed through DTB or through boot
+	  parameter from bootloader.
+
+	  It's also used for TASK_SIZE calculation in noMMU configuration.
+
+	  If unsure, leave the default value here.
+
 endmenu
 
 menu "Executable file formats"

arch/xtensa/platforms/xtfpga/include/platform/hardware.h

@@ -17,8 +17,8 @@
 
 /* Memory configuration. */
 
-#define PLATFORM_DEFAULT_MEM_START 0x00000000
-#define PLATFORM_DEFAULT_MEM_SIZE  0x04000000
+#define PLATFORM_DEFAULT_MEM_START CONFIG_DEFAULT_MEM_START
+#define PLATFORM_DEFAULT_MEM_SIZE  CONFIG_DEFAULT_MEM_SIZE
 
 /* Interrupt configuration. */