[PATCH v2 1/6] arm64: Detect the ARMv8.4 TTL feature

[Zhenyu Ye]

From: Marc Zyngier <maz@xxxxxxxxxx>

In order to reduce the cost of TLB invalidation, the ARMv8.4 TTL
feature allows TLBs to be issued with a level allowing for quicker
invalidation.

The TTL field indicates the level of page table walk
holding the leaf entry for the address being invalidated.

Let's detect the feature for now. Further patches will implement
its actual usage.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Zhenyu Ye <yezhenyu2@xxxxxxxxxx>
---
 arch/arm64/include/asm/cpucaps.h |  3 ++-
 arch/arm64/include/asm/sysreg.h  |  1 +
 arch/arm64/kernel/cpufeature.c   | 11 +++++++++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 8eb5a088ae65..cabb0c49a1d1 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -61,7 +61,8 @@
 #define ARM64_HAS_AMU_EXTN			51
 #define ARM64_HAS_ADDRESS_AUTH			52
 #define ARM64_HAS_GENERIC_AUTH			53
+#define ARM64_HAS_ARMv8_4_TTL			54
 
-#define ARM64_NCAPS				54
+#define ARM64_NCAPS				55
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index ebc622432831..df02a57fc329 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -723,6 +723,7 @@
 
 /* id_aa64mmfr2 */
 #define ID_AA64MMFR2_E0PD_SHIFT		60
+#define ID_AA64MMFR2_TTL_SHIFT		48
 #define ID_AA64MMFR2_FWB_SHIFT		40
 #define ID_AA64MMFR2_AT_SHIFT		32
 #define ID_AA64MMFR2_LVA_SHIFT		16
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9fac745aa7bb..d993dc6dc7d5 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -244,6 +244,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = {
 
 static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_E0PD_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_TTL_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_FWB_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_AT_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_LVA_SHIFT, 4, 0),
@@ -1622,6 +1623,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		.cpu_enable = cpu_has_fwb,
 	},
+	{
+		.desc = "ARMv8.4 Translation Table Level",
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.capability = ARM64_HAS_ARMv8_4_TTL,
+		.sys_reg = SYS_ID_AA64MMFR2_EL1,
+		.sign = FTR_UNSIGNED,
+		.field_pos = ID_AA64MMFR2_TTL_SHIFT,
+		.min_field_value = 1,
+		.matches = has_cpuid_feature,
+	},
 #ifdef CONFIG_ARM64_HW_AFDBM
 	{
 		/*
-- 
2.19.1