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arm64: capabilities: Introduce weak features based on local CPU 

Now that we have the flexibility of defining system features based
on individual CPUs, introduce CPU feature type that can be detected
on a local SCOPE and ignores the conflict on late CPUs. This is
applicable for ARM64_HAS_NO_HW_PREFETCH, where it is fine for
the system to have CPUs without hardware prefetch turning up
later. We only suffer a performance penalty, nothing fatal.

Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
hifive-unleashed-5.1
Suzuki K Poulose 2018-03-26 15:12:39 +01:00 committed by Will Deacon
parent ed478b3f9e
commit 5c137714dd
2 changed files with 9 additions and 1 deletions
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8
arch/arm64/include/asm/cpufeature.h
View File

@ -239,6 +239,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
*/
#define ARM64_CPUCAP_SYSTEM_FEATURE \
(ARM64_CPUCAP_SCOPE_SYSTEM | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
/*
* CPU feature detected at boot time based on feature of one or more CPUs.
* All possible conflicts for a late CPU are ignored.
*/
#define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE \
(ARM64_CPUCAP_SCOPE_LOCAL_CPU | \
ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \
ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
struct arm64_cpu_capabilities {
const char *desc;

2
arch/arm64/kernel/cpufeature.c
View File

@ -1010,7 +1010,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
{
.desc = "Software prefetching using PRFM",
.capability = ARM64_HAS_NO_HW_PREFETCH,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
.matches = has_no_hw_prefetch,
},
#ifdef CONFIG_ARM64_UAO