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arm64: errata: Factor out broken AMU const counter cap

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Move the workaround from the erratum 2457168-specific cpucap to a generic
broken AMU constant-counter one. This keeps the existing Cortex-A510
handling unchanged while allowing other errata with similar AMU constant
counter issue to share the capability bit and call sites.

Signed-off-by: Beata Michalska <beata.michalska@arm.com>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Beata Michalska 2026-10-01 11:00:31 +02:00 committed by Will Deacon
parent 3872cc6b92
commit 573371caf7
5 changed files with 28 additions and 11 deletions
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8
arch/arm64/Kconfig
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@ -1040,9 +1040,17 @@ config ARM64_ERRATUM_1902691
If unsure, say Y.
config ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT
bool
# Targeting errata affecting AMEVCNTR01, the AMU constant counter.
# On affected CPUs the counter may not increment at the expected rate,
# making it unreliable. As a result, AMU users should treat it as
# unavailable rather than relying on misleading counter values.
config ARM64_ERRATUM_2457168
bool "Cortex-A510: 2457168: workaround for AMEVCNTR01 incrementing incorrectly"
depends on ARM64_AMU_EXTN
select ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT
default y
help
This option adds the workaround for ARM Cortex-A510 erratum 2457168.

20
arch/arm64/kernel/cpu_errata.c
View File

@ -384,6 +384,16 @@ static const struct arm64_cpu_capabilities arm64_repeat_tlbi_list[] = {
};
#endif
#ifdef CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT
static const struct midr_range workaround_amu_constcnt_list[] = {
#ifdef CONFIG_ARM64_ERRATUM_2457168
/* Cortex-A510 r0p0-r1p1 */
MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1),
#endif
{}
};
#endif /* CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT */
#ifdef CONFIG_CAVIUM_ERRATUM_23154
static const struct midr_range cavium_erratum_23154_cpus[] = {
MIDR_ALL_VERSIONS(MIDR_THUNDERX),
@ -919,14 +929,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 2)
},
#endif
#ifdef CONFIG_ARM64_ERRATUM_2457168
#ifdef CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT
{
.desc = "ARM erratum 2457168",
.capability = ARM64_WORKAROUND_2457168,
.desc = "Broken AMU AMEVCNTR01 (const counter)",
.capability = ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT,
.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
/* Cortex-A510 r0p0-r1p1 */
CAP_MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1)
CAP_MIDR_RANGE_LIST(workaround_amu_constcnt_list)
},
#endif
#ifdef CONFIG_ARM64_ERRATUM_2038923

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

@ -2089,7 +2089,7 @@ static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap)
cpumask_set_cpu(smp_processor_id(), &amu_cpus);
/* 0 reference values signal broken/disabled counters */
if (!this_cpu_has_cap(ARM64_WORKAROUND_2457168))
if (!this_cpu_has_cap(ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT))
update_freq_counters_refs();
}
}

7
arch/arm64/kernel/topology.c
View File

@ -400,7 +400,7 @@ static void cpu_read_constcnt(void *val)
* the counter is disabled. A return value of 0 at counter read is
* properly handled as an error case by the users of the counter.
*/
*(u64 *)val = this_cpu_has_cap(ARM64_WORKAROUND_2457168) ?
*(u64 *)val = this_cpu_has_cap(ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT) ?
0UL : read_constcnt();
}
@ -461,8 +461,9 @@ static void amu_read_core_const_ctrs(void *val)
/*
* cpu_read_constcnt() incurs slight latency due to the
* ARM64_WORKAROUND_2457168 check. Read it first to minimize
* the sampling skew between the const and core counters.
* ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT check.
* Read it first to minimize the sampling skew between the const
* and core counters.
*/
cpu_read_constcnt(&ctrs->constcnt);
cpu_read_corecnt(&ctrs->corecnt);

2
arch/arm64/tools/cpucaps
View File

@ -105,7 +105,6 @@ WORKAROUND_1902691
WORKAROUND_2038923
WORKAROUND_2064142
WORKAROUND_2077057
WORKAROUND_2457168
WORKAROUND_2645198
WORKAROUND_2658417
WORKAROUND_4193714
@ -132,3 +131,4 @@ WORKAROUND_REPEAT_TLBI_SYNC
WORKAROUND_SPECULATIVE_AT
WORKAROUND_SPECULATIVE_SSBS
WORKAROUND_SPECULATIVE_UNPRIV_LOAD
WORKAROUND_BROKEN_AMU_CONSTCNT