[PATCH 2/5] arm64: cpufeature: Detect BBML3 based on MMFR2 ID

[Linu Cherian <linu.cherian@arm.com>]

Add MMFR2 ID based BBML3 feature detection, so
that compliant cpus doesn't need to be added to the
midr list.

Signed-off-by: Linu Cherian <linu.cherian@arm.com>
---
 arch/arm64/kernel/cpufeature.c | 14 +++++++-------
 arch/arm64/tools/sysreg        |  1 +
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9986eb7b379c..d754b1b7da77 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2133,6 +2133,7 @@ static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
 
 bool cpu_supports_bbml3(void)
 {
+	u64 mmfr2;
 	/* CPUs that support BBML3 but dont advertise through MMFR2 ID */
 	static const struct midr_range supports_bbml3_list[] = {
 		MIDR_REV_RANGE(MIDR_CORTEX_X4, 0, 3, 0xf),
@@ -2144,15 +2145,14 @@ bool cpu_supports_bbml3(void)
 		{}
 	};
 
-	if (!is_midr_in_range_list(supports_bbml3_list))
-		return false;
+	if (is_midr_in_range_list(supports_bbml3_list))
+		return true;
 
-	/*
-	 * We currently ignore the ID_AA64MMFR2_EL1 register, and only care
-	 * about whether the MIDR check passes.
-	 */
+	mmfr2 = __read_sysreg_by_encoding(SYS_ID_AA64MMFR2_EL1);
+	if (SYS_FIELD_GET(ID_AA64MMFR2_EL1, BBM, mmfr2) == ID_AA64MMFR2_EL1_BBM_3)
+		return true;
 
-	return true;
+	return false;
 }
 
 static bool has_bbml3(const struct arm64_cpu_capabilities *caps, int scope)
diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
index bc1788b1662b..082256ec3bf9 100644
--- a/arch/arm64/tools/sysreg
+++ b/arch/arm64/tools/sysreg
@@ -2259,6 +2259,7 @@ UnsignedEnum	55:52	BBM
 	0b0000	0
 	0b0001	1
 	0b0010	2
+	0b0011	3
 EndEnum
 UnsignedEnum	51:48	TTL
 	0b0000	NI
-- 
2.43.0