arm64: v8.3: Support for weaker release consistency

ARMv8.3 adds new instructions to support Release Consistent
processor consistent (RCpc) model, which is weaker than the
RCsc model.
Signed-off-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Documentation/arm64/cpu-feature-registers.txt

@@ -174,6 +174,8 @@ infrastructure:
      x--------------------------------------------------x
      | Name                         |  bits   | visible |
      |--------------------------------------------------|
+     | LRCPC                        | [23-20] |    y    |
+     |--------------------------------------------------|
      | FCMA                         | [19-16] |    y    |
      |--------------------------------------------------|
      | JSCVT                        | [15-12] |    y    |

arch/arm64/include/asm/sysreg.h

@@ -157,6 +157,7 @@
 #define ID_AA64ISAR0_AES_SHIFT		4
 
 /* id_aa64isar1 */
+#define ID_AA64ISAR1_LRCPC_SHIFT	20
 #define ID_AA64ISAR1_FCMA_SHIFT		16
 #define ID_AA64ISAR1_JSCVT_SHIFT	12
 

arch/arm64/include/uapi/asm/hwcap.h

@@ -34,5 +34,6 @@
 #define HWCAP_ASIMDRDM		(1 << 12)
 #define HWCAP_JSCVT		(1 << 13)
 #define HWCAP_FCMA		(1 << 14)
+#define HWCAP_LRCPC		(1 << 15)
 
 #endif /* _UAPI__ASM_HWCAP_H */

arch/arm64/kernel/cpufeature.c

@@ -98,6 +98,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_LRCPC_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_FCMA_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_JSCVT_SHIFT, 4, 0),
 	ARM64_FTR_END,
@@ -896,6 +897,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_ASIMDHP),
 	HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_JSCVT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_JSCVT),
 	HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FCMA_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FCMA),
+	HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_LRCPC),
 	{},
 };
 

arch/arm64/kernel/cpuinfo.c

@@ -67,6 +67,7 @@ static const char *const hwcap_str[] = {
 	"asimdrdm",
 	"jscvt",
 	"fcma",
+	"lrcpc",
 	NULL
 };