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ACPI: CPPC: Disable FIE if registers in PCC regions

Browse source 
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>
This commit is contained in:
Jeremy Linton 2022-09-12 15:37:22 -05:00 committed by Rafael J. Wysocki
parent a2a9d18500
commit ae2df912d1
3 changed files with 68 additions and 4 deletions
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42
drivers/acpi/cppc_acpi.c
View file

@ -1243,6 +1243,48 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
}
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.

25
drivers/cpufreq/cppc_cpufreq.c
View file

@ -63,7 +63,15 @@ static struct cppc_workaround_oem_info wa_info[] = {
static struct cpufreq_driver cppc_cpufreq_driver;
static enum {
FIE_UNSET = -1,
FIE_ENABLED,
FIE_DISABLED
} fie_disabled = FIE_UNSET;
#ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE
module_param(fie_disabled, int, 0444);
MODULE_PARM_DESC(fie_disabled, "Disable Frequency Invariance Engine (FIE)");
/* Frequency invariance support */
struct cppc_freq_invariance {
@ -158,7 +166,7 @@ static void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy)
struct cppc_freq_invariance *cppc_fi;
int cpu, ret;
if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
if (fie_disabled)
return;
for_each_cpu(cpu, policy->cpus) {
@ -199,7 +207,7 @@ static void cppc_cpufreq_cpu_fie_exit(struct cpufreq_policy *policy)
struct cppc_freq_invariance *cppc_fi;
int cpu;
if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
if (fie_disabled)
return;
/* policy->cpus will be empty here, use related_cpus instead */
@ -229,7 +237,15 @@ static void __init cppc_freq_invariance_init(void)
};
int ret;
if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED) {
fie_disabled = FIE_ENABLED;
if (cppc_perf_ctrs_in_pcc()) {
pr_info("FIE not enabled on systems with registers in PCC\n");
fie_disabled = FIE_DISABLED;
}
}
if (fie_disabled)
return;
kworker_fie = kthread_create_worker(0, "cppc_fie");
@ -247,7 +263,7 @@ static void __init cppc_freq_invariance_init(void)
static void cppc_freq_invariance_exit(void)
{
if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
if (fie_disabled)
return;
kthread_destroy_worker(kworker_fie);
@ -936,6 +952,7 @@ static void cppc_check_hisi_workaround(void)
wa_info[i].oem_revision == tbl->oem_revision) {
/* Overwrite the get() callback */
cppc_cpufreq_driver.get = hisi_cppc_cpufreq_get_rate;
fie_disabled = FIE_DISABLED;
break;
}
}

5
include/acpi/cppc_acpi.h
View file

@ -140,6 +140,7 @@ extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
extern int cppc_set_enable(int cpu, bool enable);
extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
extern bool cppc_perf_ctrs_in_pcc(void);
extern bool acpi_cpc_valid(void);
extern bool cppc_allow_fast_switch(void);
extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
@ -173,6 +174,10 @@ static inline int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps)
{
return -ENOTSUPP;
}
static inline bool cppc_perf_ctrs_in_pcc(void)
{
return false;
}
static inline bool acpi_cpc_valid(void)
{
return false;