[RFC PATCH v2 1/8] arm64: cpufeature: Add API to report system support of HWDBM

[Shameer Kolothum]

From: Keqian Zhu <zhukeqian1 at huawei.com>

Though we already has a cpu capability named ARM64_HW_DBM, it's a
LOCAL_CPU cap and conditionally compiled by CONFIG_ARM64_HW_AFDBM.

This reports the system wide support of HW_DBM.

Signed-off-by: Keqian Zhu <zhukeqian1 at huawei.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
---
 arch/arm64/include/asm/cpufeature.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 96e50227f940..edb04e45e030 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -733,6 +733,21 @@ static inline bool system_supports_mixed_endian(void)
 	return val == 0x1;
 }
 
+static inline bool system_supports_hw_dbm(void)
+{
+	u64 mmfr1;
+	u32 val;
+
+	if (!IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
+		return false;
+
+	mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+	val = cpuid_feature_extract_unsigned_field(mmfr1,
+						ID_AA64MMFR1_EL1_HAFDBS_SHIFT);
+
+	return val == ID_AA64MMFR1_EL1_HAFDBS_DBM;
+}
+
 static __always_inline bool system_supports_fpsimd(void)
 {
 	return !cpus_have_const_cap(ARM64_HAS_NO_FPSIMD);
-- 
2.34.1