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>

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index c2309429146fa649ab1ce8bb9ecb85b1259cc460..093675b1a1ffbe04614e7b3a317ea835a14685ae 100644 (file)
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1243,6 +1243,48 @@ 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.

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 9adb7612993e0c519db08f8b7c68c8c59fb878d9..432dfb4e8027e96b908c420cd40f0d0eb911bfef 100644 (file)
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -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;
                }
        }

diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index f73d357ecdf5ff06a5e3c898df9bfd8182ee2e03..c5614444031ff85f3303f7f09417a442f9f2510c 100644 (file)
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -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;