linux-kernel - [PATCH 2/3] arm64: cpufeature: Add a filter function to cpufeature

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Date:   Fri,  8 Jan 2021 16:29:22 -0800
From:   Srinivas Ramana <sramana@...eaurora.org>
To:     catalin.marinas@....com, will@...nel.org, pajay@....qualcomm.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Srinivas Ramana <sramana@...eaurora.org>,
        Prasad Sodagudi <psodagud@...eaurora.org>
Subject: [PATCH 2/3] arm64: cpufeature: Add a filter function to cpufeature

Add a filter function to cpufeature so that it can be used
when dynamic control of the feature is required.

Signed-off-by: Ajay Patil <pajay@....qualcomm.com>
Signed-off-by: Prasad Sodagudi <psodagud@...eaurora.org>
Signed-off-by: Srinivas Ramana <sramana@...eaurora.org>
---
 arch/arm64/include/asm/cpufeature.h |  8 +++++++-
 arch/arm64/kernel/cpufeature.c      | 15 ++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 9a555809b89c..81a5c97d647d 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -61,6 +61,7 @@ struct arm64_ftr_bits {
 	u8		shift;
 	u8		width;
 	s64		safe_val; /* safe value for FTR_EXACT features */
+	s64		(*filter)(const struct arm64_ftr_bits *ftrp, s64 fval);
 };
 
 /*
@@ -566,7 +567,12 @@ cpuid_feature_extract_field(u64 features, int field, bool sign)
 
 static inline s64 arm64_ftr_value(const struct arm64_ftr_bits *ftrp, u64 val)
 {
-	return (s64)cpuid_feature_extract_field_width(val, ftrp->shift, ftrp->width, ftrp->sign);
+	s64 fval = (s64)cpuid_feature_extract_field_width(val, ftrp->shift,
+					ftrp->width, ftrp->sign);
+
+	if (ftrp->filter)
+		fval = ftrp->filter(ftrp, fval);
+	return fval;
 }
 
 static inline bool id_aa64mmfr0_mixed_endian_el0(u64 mmfr0)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 7ffb5f1d8b68..b2ffa9eaaaff 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -132,23 +132,28 @@ DEFINE_STATIC_KEY_ARRAY_FALSE(cpu_hwcap_keys, ARM64_NCAPS);
 EXPORT_SYMBOL(cpu_hwcap_keys);
 
 #define __ARM64_FTR_BITS(SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \
-	{						\
 		.sign = SIGNED,				\
 		.visible = VISIBLE,			\
 		.strict = STRICT,			\
 		.type = TYPE,				\
 		.shift = SHIFT,				\
 		.width = WIDTH,				\
-		.safe_val = SAFE_VAL,			\
-	}
+		.safe_val = SAFE_VAL
 
 /* Define a feature with unsigned values */
 #define ARM64_FTR_BITS(VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \
-	__ARM64_FTR_BITS(FTR_UNSIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL)
+	{__ARM64_FTR_BITS(FTR_UNSIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL), }
 
 /* Define a feature with a signed value */
 #define S_ARM64_FTR_BITS(VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \
-	__ARM64_FTR_BITS(FTR_SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL)
+	{__ARM64_FTR_BITS(FTR_SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL), }
+
+/* Define a feature with a filter function to process the field value */
+#define FILTERED_ARM64_FTR_BITS(SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL, filter_fn) \
+	{											\
+		__ARM64_FTR_BITS(SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL),	\
+		.filter = filter_fn,								\
+	}
 
 #define ARM64_FTR_END					\
 	{						\
-- 
2.7.4