MIPS: Add CP0 CMGCRBase definitions & accessor

The CMGCRBase register is defined by the PRA specification as an optional
register which indicates the physical base of the MIPS Coherence Manager
Global Control Register block. This patch simply adds a definition for
the base address field within the register, along with an accessor
function for reading the register.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6356/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mipsregs.h

@@ -671,6 +671,10 @@
 /*  EntryHI bit definition */
 #define MIPS_ENTRYHI_EHINV	(_ULCAST_(1) << 10)
 
+/* CMGCRBase bit definitions */
+#define MIPS_CMGCRB_BASE	11
+#define MIPS_CMGCRF_BASE	(~_ULCAST_((1 << MIPS_CMGCRB_BASE) - 1))
+
 /*
  * Bits in the MIPS32/64 coprocessor 1 (FPU) revision register.
  */
@@ -1025,6 +1029,8 @@ do {									\
 
 #define read_c0_prid()		__read_32bit_c0_register($15, 0)
 
+#define read_c0_cmgcrbase()	__read_ulong_c0_register($15, 3)
+
 #define read_c0_config()	__read_32bit_c0_register($16, 0)
 #define read_c0_config1()	__read_32bit_c0_register($16, 1)
 #define read_c0_config2()	__read_32bit_c0_register($16, 2)