[RFC PATCH 1/4] arm64: cpufeature: TWED support detection

[Jingyi Wang]

From: Zengruan Ye <yezengruan at huawei.com>

TWE Delay is an optional feature in ARMv8.6 Extentions. This patch
detect this feature.

Signed-off-by: Zengruan Ye <yezengruan at huawei.com>
Signed-off-by: Jingyi Wang <wangjingyi11 at huawei.com>
---
 arch/arm64/Kconfig               | 10 ++++++++++
 arch/arm64/include/asm/cpucaps.h |  3 ++-
 arch/arm64/kernel/cpufeature.c   | 12 ++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..fe66f4fc5f49 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1666,6 +1666,16 @@ config ARCH_RANDOM
 
 endmenu
 
+menu "ARMv8.6 architectural features"
+
+config ARM64_TWED
+	bool "Enable suppot for delayed trapping of WFE"
+	default y
+	help
+	  Delayed Trapping of WFE (part of the ARMv8.6 Extensions)
+
+endmenu
+
 config ARM64_SVE
 	bool "ARM Scalable Vector Extension support"
 	default y
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 07b643a70710..7b8f018d142b 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -64,7 +64,8 @@
 #define ARM64_BTI				54
 #define ARM64_HAS_ARMv8_4_TTL			55
 #define ARM64_HAS_TLB_RANGE			56
+#define ARM64_HAS_TWED				57
 
-#define ARM64_NCAPS				57
+#define ARM64_NCAPS				58
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6424584be01e..d042d32a1144 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2120,6 +2120,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.min_field_value = ID_AA64PFR1_BT_BTI,
 		.sign = FTR_UNSIGNED,
 	},
+#endif
+#ifdef CONFIG_ARM64_TWED
+	{
+		.desc = "Delayed Trapping of WFE",
+		.capability = ARM64_HAS_TWED,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		.sys_reg = SYS_ID_AA64MMFR1_EL1,
+		.field_pos = ID_AA64MMFR1_TWED_SHIFT,
+		.sign = FTR_UNSIGNED,
+		.min_field_value = 1,
+	},
 #endif
 	{},
 };
-- 
2.19.1