arm64: add kconfig symbol to configure physical address size

ARMv8.2 introduces support for 52-bit physical addresses. To prepare for
supporting this, add a new kconfig symbol to configure the physical
address space size. The symbols will be used in subsequent patches.
Currently the only choice is 48, a later patch will add the option of 52
once the required code is in place.

Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Bob Picco <bob.picco@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[catalin.marinas@arm.com: folded minor patches into this one]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -646,6 +646,22 @@ config ARM64_VA_BITS
 	default 47 if ARM64_VA_BITS_47
 	default 48 if ARM64_VA_BITS_48
 
+choice
+	prompt "Physical address space size"
+	default ARM64_PA_BITS_48
+	help
+	  Choose the maximum physical address range that the kernel will
+	  support.
+
+config ARM64_PA_BITS_48
+	bool "48-bit"
+
+endchoice
+
+config ARM64_PA_BITS
+	int
+	default 48 if ARM64_PA_BITS_48
+
 config CPU_BIG_ENDIAN
        bool "Build big-endian kernel"
        help

arch/arm64/include/asm/pgtable-hwdef.h

@@ -196,7 +196,7 @@
 /*
  * Highest possible physical address supported.
  */
-#define PHYS_MASK_SHIFT		(48)
+#define PHYS_MASK_SHIFT		(CONFIG_ARM64_PA_BITS)
 #define PHYS_MASK		((UL(1) << PHYS_MASK_SHIFT) - 1)
 
 /*

arch/arm64/include/asm/sparsemem.h

@@ -17,7 +17,7 @@
 #define __ASM_SPARSEMEM_H
 
 #ifdef CONFIG_SPARSEMEM
-#define MAX_PHYSMEM_BITS	48
+#define MAX_PHYSMEM_BITS	CONFIG_ARM64_PA_BITS
 #define SECTION_SIZE_BITS	30
 #endif