Re: [PATCH v5 1/1] ACPI: CPPC: Disable FIE if registers in PCC regions

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Raphael,

Ping, are we good here?

Thanks,


On 9/12/22 15:37, Jeremy Linton wrote:
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@xxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
  drivers/acpi/cppc_acpi.c       | 42 ++++++++++++++++++++++++++++++++++
  drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
  include/acpi/cppc_acpi.h       |  5 ++++
  3 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 1e15a9f25ae9..55693e6f7153 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1240,6 +1240,48 @@ 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.
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 24eaf0ec344d..9e2a48ac5830 100644
--- 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 f73d357ecdf5..c5614444031f 100644
--- 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;




[Index of Archives]     [Linux IBM ACPI]     [Linux Power Management]     [Linux Kernel]     [Linux Laptop]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux