arm64: kernel: Add min_field_value and use '>=' for feature detection

When a new cpu feature is available, the cpu feature bits will have some
initial value, which is incremented when the feature is updated.
This patch changes 'register_value' to be 'min_field_value', and checks
the feature bits value (interpreted as a signed int) is greater than this
minimum.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 484fa9425314110f70a9a25e722b5e29930465ad..f595f7ddd43bafef709e276fdbe78241273a659d 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -42,8 +42,8 @@ struct arm64_cpu_capabilities {
                };
 
                struct {        /* Feature register checking */
-                       u64 register_mask;
-                       u64 register_value;
+                       int field_pos;
+                       int min_field_value;
                };
        };
 };

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 650ffc28bedcf96f89522a612a34dc2bebd86b47..74fd0f74b0651b70b8f34038207710a493746d0f 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -22,13 +22,21 @@
 #include <asm/cpu.h>
 #include <asm/cpufeature.h>
 
+static bool
+feature_matches(u64 reg, const struct arm64_cpu_capabilities *entry)
+{
+       int val = cpuid_feature_extract_field(reg, entry->field_pos);
+
+       return val >= entry->min_field_value;
+}
+
 static bool
 has_id_aa64pfr0_feature(const struct arm64_cpu_capabilities *entry)
 {
        u64 val;
 
        val = read_cpuid(id_aa64pfr0_el1);
-       return (val & entry->register_mask) == entry->register_value;
+       return feature_matches(val, entry);
 }
 
 static const struct arm64_cpu_capabilities arm64_features[] = {
@@ -36,8 +44,8 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
                .desc = "GIC system register CPU interface",
                .capability = ARM64_HAS_SYSREG_GIC_CPUIF,
                .matches = has_id_aa64pfr0_feature,
-               .register_mask = (0xf << 24),
-               .register_value = (1 << 24),
+               .field_pos = 24,
+               .min_field_value = 1,
        },
        {},
 };