Commit ae2df912 authored by Jeremy Linton's avatar Jeremy Linton Committed by Rafael J. Wysocki
Browse files

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: default avatarJeremy Linton <jeremy.linton@arm.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: default avatarIonela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent a2a9d185

drivers/acpi/cppc_acpi.c

+42 −0
Original line number Diff line number Diff line
@@ -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.

drivers/cpufreq/cppc_cpufreq.c

+21 −4
Original line number Diff line number Diff line
@@ -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;

		}

	}

include/acpi/cppc_acpi.h

+5 −0
Original line number Diff line number Diff line
@@ -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;