arm64: Generalise msr_s/mrs_s operations

The system register encoding generated by sys_reg() works only
for MRS/MSR(Register) operations, as we hardcode Bit20 to 1 in
mrs_s/msr_s mask. This makes it unusable for generating instructions
accessing registers with Op0 < 2(e.g, PSTATE.x with Op0=0).

As per ARMv8 ARM, (Ref: ARMv8 ARM, Section: "System instruction class
encoding overview", C5.2, version:ARM DDI 0487A.f), the instruction
encoding reserves bits [20-19] for Op0.

This patch generalises the sys_reg, mrs_s and msr_s macros, so that
we could use them to access any of the supported system register.

Cc: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/sysreg.h

@@ -23,8 +23,18 @@
 #define SCTLR_EL1_CP15BEN	(0x1 << 5)
 #define SCTLR_EL1_SED		(0x1 << 8)
 
+/*
+ * ARMv8 ARM reserves the following encoding for system registers:
+ * (Ref: ARMv8 ARM, Section: "System instruction class encoding overview",
+ *  C5.2, version:ARM DDI 0487A.f)
+ *	[20-19] : Op0
+ *	[18-16] : Op1
+ *	[15-12] : CRn
+ *	[11-8]  : CRm
+ *	[7-5]   : Op2
+ */
 #define sys_reg(op0, op1, crn, crm, op2) \
-	((((op0)-2)<<19)|((op1)<<16)|((crn)<<12)|((crm)<<8)|((op2)<<5))
+	((((op0)&3)<<19)|((op1)<<16)|((crn)<<12)|((crm)<<8)|((op2)<<5))
 
 #ifdef __ASSEMBLY__
 
@@ -34,11 +44,11 @@
 	.equ	__reg_num_xzr, 31
 
 	.macro	mrs_s, rt, sreg
-	.inst	0xd5300000|(\sreg)|(__reg_num_\rt)
+	.inst	0xd5200000|(\sreg)|(__reg_num_\rt)
 	.endm
 
 	.macro	msr_s, sreg, rt
-	.inst	0xd5100000|(\sreg)|(__reg_num_\rt)
+	.inst	0xd5000000|(\sreg)|(__reg_num_\rt)
 	.endm
 
 #else
@@ -50,11 +60,11 @@ asm(
 "	.equ	__reg_num_xzr, 31\n"
 "\n"
 "	.macro	mrs_s, rt, sreg\n"
-"	.inst	0xd5300000|(\\sreg)|(__reg_num_\\rt)\n"
+"	.inst	0xd5200000|(\\sreg)|(__reg_num_\\rt)\n"
 "	.endm\n"
 "\n"
 "	.macro	msr_s, sreg, rt\n"
-"	.inst	0xd5100000|(\\sreg)|(__reg_num_\\rt)\n"
+"	.inst	0xd5000000|(\\sreg)|(__reg_num_\\rt)\n"
 "	.endm\n"
 );