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author | Jeremy Linton <jeremy.linton@arm.com> | 2022-09-12 23:37:22 +0300 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2022-09-24 19:43:46 +0300 |
commit | ae2df912d1a557a3548be83da20851ac55f42ab3 (patch) | |
tree | 2e7a5615eb34e9034e0579a404bc3f8df30596a3 /drivers/acpi/cppc_acpi.c | |
parent | a2a9d1850060e5d995136561d76e81d61414f076 (diff) | |
download | linux-ae2df912d1a557a3548be83da20851ac55f42ab3.tar.xz |
ACPI: CPPC: Disable FIE if registers in PCC regions
PCC regions utilize a mailbox to set/retrieve register values used by
the CPPC code. This is fine as long as the operations are
infrequent. With the FIE code enabled though the overhead can range
from 2-11% of system CPU overhead (ex: as measured by top) on Arm
based machines.
So, before enabling FIE assure none of the registers used by
cppc_get_perf_ctrs() are in the PCC region. Finally, add a module
parameter which can override the PCC region detection at boot or
module reload.
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/cppc_acpi.c')
-rw-r--r-- | drivers/acpi/cppc_acpi.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index c2309429146f..093675b1a1ff 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1244,6 +1244,48 @@ out_err: EXPORT_SYMBOL_GPL(cppc_get_perf_caps); /** + * cppc_perf_ctrs_in_pcc - Check if any perf counters are in a PCC region. + * + * CPPC has flexibility about how CPU performance counters are accessed. + * One of the choices is PCC regions, which can have a high access latency. This + * routine allows callers of cppc_get_perf_ctrs() to know this ahead of time. + * + * Return: true if any of the counters are in PCC regions, false otherwise + */ +bool cppc_perf_ctrs_in_pcc(void) +{ + int cpu; + + for_each_present_cpu(cpu) { + struct cpc_register_resource *ref_perf_reg; + struct cpc_desc *cpc_desc; + + cpc_desc = per_cpu(cpc_desc_ptr, cpu); + + if (CPC_IN_PCC(&cpc_desc->cpc_regs[DELIVERED_CTR]) || + CPC_IN_PCC(&cpc_desc->cpc_regs[REFERENCE_CTR]) || + CPC_IN_PCC(&cpc_desc->cpc_regs[CTR_WRAP_TIME])) + return true; + + + ref_perf_reg = &cpc_desc->cpc_regs[REFERENCE_PERF]; + + /* + * If reference perf register is not supported then we should + * use the nominal perf value + */ + if (!CPC_SUPPORTED(ref_perf_reg)) + ref_perf_reg = &cpc_desc->cpc_regs[NOMINAL_PERF]; + + if (CPC_IN_PCC(ref_perf_reg)) + return true; + } + + return false; +} +EXPORT_SYMBOL_GPL(cppc_perf_ctrs_in_pcc); + +/** * cppc_get_perf_ctrs - Read a CPU's performance feedback counters. * @cpunum: CPU from which to read counters. * @perf_fb_ctrs: ptr to cppc_perf_fb_ctrs. See cppc_acpi.h |