linux-kernel - [PATCH v3] arm64/prefetch: fix a -Wtype-limits warning

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Message-Id: <20190806030503.1178-1-cai@lca.pw>
Date:   Mon,  5 Aug 2019 23:05:03 -0400
From:   Qian Cai <cai@....pw>
To:     will@...nel.org, catalin.marinas@....com
Cc:     rrichter@...ium.com, robin.murphy@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH v3] arm64/prefetch: fix a -Wtype-limits warning

The commit d5370f754875 ("arm64: prefetch: add alternative pattern for
CPUs without a prefetcher") introduced MIDR_IS_CPU_MODEL_RANGE() to be
used in has_no_hw_prefetch() with rv_min=0 which generates a compilation
warning from GCC,

In file included from ./arch/arm64/include/asm/cache.h:8,
               from ./include/linux/cache.h:6,
               from ./include/linux/printk.h:9,
               from ./include/linux/kernel.h:15,
               from ./include/linux/cpumask.h:10,
               from arch/arm64/kernel/cpufeature.c:11:
arch/arm64/kernel/cpufeature.c: In function 'has_no_hw_prefetch':
./arch/arm64/include/asm/cputype.h:59:26: warning: comparison of
unsigned expression >= 0 is always true [-Wtype-limits]
_model == (model) && rv >= (rv_min) && rv <= (rv_max);  \
                        ^~
arch/arm64/kernel/cpufeature.c:889:9: note: in expansion of macro
'MIDR_IS_CPU_MODEL_RANGE'
return MIDR_IS_CPU_MODEL_RANGE(midr, MIDR_THUNDERX,
       ^~~~~~~~~~~~~~~~~~~~~~~

Fix it by converting MIDR_IS_CPU_MODEL_RANGE to a static inline
function.

Signed-off-by: Qian Cai <cai@....pw>
---

v3: Convert MIDR_IS_CPU_MODEL_RANGE to a static inline function.
v2: Use "s32" for "rv", so "variant 0/revision 0" can be covered.

 arch/arm64/include/asm/cputype.h | 21 +++++++++++----------
 arch/arm64/kernel/cpufeature.c   |  2 +-
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index e7d46631cc42..b1454d117cd2 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -51,14 +51,6 @@
 #define MIDR_CPU_MODEL_MASK (MIDR_IMPLEMENTOR_MASK | MIDR_PARTNUM_MASK | \
 			     MIDR_ARCHITECTURE_MASK)
 
-#define MIDR_IS_CPU_MODEL_RANGE(midr, model, rv_min, rv_max)		\
-({									\
-	u32 _model = (midr) & MIDR_CPU_MODEL_MASK;			\
-	u32 rv = (midr) & (MIDR_REVISION_MASK | MIDR_VARIANT_MASK);	\
-									\
-	_model == (model) && rv >= (rv_min) && rv <= (rv_max);		\
- })
-
 #define ARM_CPU_IMP_ARM			0x41
 #define ARM_CPU_IMP_APM			0x50
 #define ARM_CPU_IMP_CAVIUM		0x43
@@ -159,10 +151,19 @@ struct midr_range {
 #define MIDR_REV(m, v, r) MIDR_RANGE(m, v, r, v, r)
 #define MIDR_ALL_VERSIONS(m) MIDR_RANGE(m, 0, 0, 0xf, 0xf)
 
+static inline bool midr_is_cpu_model_range(u32 midr, u32 model, u32 rv_min,
+					   u32 rv_max)
+{
+	u32 _model = midr & MIDR_CPU_MODEL_MASK;
+	u32 rv = midr & (MIDR_REVISION_MASK | MIDR_VARIANT_MASK);
+
+	return _model == model && rv >= rv_min && rv <= rv_max;
+}
+
 static inline bool is_midr_in_range(u32 midr, struct midr_range const *range)
 {
-	return MIDR_IS_CPU_MODEL_RANGE(midr, range->model,
-				 range->rv_min, range->rv_max);
+	return midr_is_cpu_model_range(midr, range->model,
+				       range->rv_min, range->rv_max);
 }
 
 static inline bool
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d19d14ba9ae4..95201e5ff5e1 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -886,7 +886,7 @@ static bool has_no_hw_prefetch(const struct arm64_cpu_capabilities *entry, int _
 	u32 midr = read_cpuid_id();
 
 	/* Cavium ThunderX pass 1.x and 2.x */
-	return MIDR_IS_CPU_MODEL_RANGE(midr, MIDR_THUNDERX,
+	return midr_is_cpu_model_range(midr, MIDR_THUNDERX,
 		MIDR_CPU_VAR_REV(0, 0),
 		MIDR_CPU_VAR_REV(1, MIDR_REVISION_MASK));
 }
-- 
2.20.1 (Apple Git-117)