From b8c9592b4a6c93211c8163888a97880d608503b5 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 19 Mar 2015 19:03:25 +0100 Subject: [PATCH] ARM: 8318/1: treat CPU feature register fields as signed quantities The various CPU feature registers consist of 4-bit blocks that represent signed quantities, whose positive values represent incremental features, and whose negative values are reserved. To improve forward compatibility, update the feature detection code to take possible future higher values into account, but ignore negative values. Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/include/asm/cputype.h | 16 ++++++++++++++++ arch/arm/kernel/setup.c | 22 +++++++++------------- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h index 819777d0e91f..85e374f873ac 100644 --- a/arch/arm/include/asm/cputype.h +++ b/arch/arm/include/asm/cputype.h @@ -253,4 +253,20 @@ static inline int cpu_is_pj4(void) #else #define cpu_is_pj4() 0 #endif + +static inline int __attribute_const__ cpuid_feature_extract_field(u32 features, + int field) +{ + int feature = (features >> field) & 15; + + /* feature registers are signed values */ + if (feature > 8) + feature -= 16; + + return feature; +} + +#define cpuid_feature_extract(reg, field) \ + cpuid_feature_extract_field(read_cpuid_ext(reg), field) + #endif diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index e55408e96559..637c449e6060 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -375,30 +375,26 @@ void __init early_print(const char *str, ...) static void __init cpuid_init_hwcaps(void) { - unsigned int divide_instrs, vmsa; + int block; if (cpu_architecture() < CPU_ARCH_ARMv7) return; - divide_instrs = (read_cpuid_ext(CPUID_EXT_ISAR0) & 0x0f000000) >> 24; - - switch (divide_instrs) { - case 2: + block = cpuid_feature_extract(CPUID_EXT_ISAR0, 24); + if (block >= 2) elf_hwcap |= HWCAP_IDIVA; - case 1: + if (block >= 1) elf_hwcap |= HWCAP_IDIVT; - } /* LPAE implies atomic ldrd/strd instructions */ - vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0; - if (vmsa >= 5) + block = cpuid_feature_extract(CPUID_EXT_MMFR0, 0); + if (block >= 5) elf_hwcap |= HWCAP_LPAE; } static void __init elf_hwcap_fixup(void) { unsigned id = read_cpuid_id(); - unsigned sync_prim; /* * HWCAP_TLS is available only on 1136 r1p0 and later, @@ -419,9 +415,9 @@ static void __init elf_hwcap_fixup(void) * avoid advertising SWP; it may not be atomic with * multiprocessing cores. */ - sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) | - ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f); - if (sync_prim >= 0x13) + if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 || + (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 && + cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3)) elf_hwcap &= ~HWCAP_SWP; } -- 2.20.1