[PATCH v5 0/1] Disable FIE on machines with slow counters

[PATCH v5 0/1] Disable FIE on machines with slow counters

[Jeremy Linton]

FIE assumes the delivered/relative perf registers are fast to read so
it goes ahead and hits them quite frequently. On a couple of Arm
platforms though they end up in PCC regions which require mailbox
handshaking with other parts of the platform.

This results in a lot of overhead in the cppc_fie task. As such lets
runtime disable FIE if we detect it enabled on one of those platforms.
Lastly, allow the user to override this decision via a module parameter.

v1->v2:
	Apply Rafael's review comments.
	Move the MODULE_PARAM into the ifdef
	Fix compiler warning when ACPI_CPPC_LIB is disabled.
v2->v3:
	Tristate the module param so FIE can be forced on/off
	Bump pr_debug to pr_info if FIE is disabled due to PCC regions
	Switch ACPI_CPPC_CPUFREQ_FIE off by default
v3->v4:
	No functional change, resend due to email addr issues

v4->v5:
	Minor whitespace, comment wording, if/case conversion
	Drop the ACPI_CPPC_CPUFREQ_FIE disable config change added in v3

Jeremy Linton (1):
  ACPI: CPPC: Disable FIE if registers in PCC regions

 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(-)

-- 
2.37.1

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

[Jeremy Linton]

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>
---
 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;
-- 
2.37.1

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

[Jeremy Linton]

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@arm.com>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>   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;

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

[Ionela Voinescu]

Hi Jeremy,

On Monday 12 Sep 2022 at 15:37:22 (-0500), 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@arm.com>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  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);

Why 'int' and not 'bool' here?

IIUC, if you use 'bool' the user can pass any int/0/1/y/n/Y/N, which
will result in fie_disabled properly having either the value 0 or 1
(or default FIE_UNSET) if a parameter is not passed.

Then
'if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED)'
can become
'if (fie_disabled == FIE_UNSET)' or 'if (fie_disabled < 0)'.

I feel I'm missing something, otherwise you would have done this
already.

Otherwise FWIW, it looks good to me.
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>

Thanks,
Ionela.

> +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;
> -- 
> 2.37.1
> 

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

[Rafael J. Wysocki]

On Fri, Sep 23, 2022 at 6:31 PM Ionela Voinescu <ionela.voinescu@arm.com> wrote:
>
> Hi Jeremy,
>
> On Monday 12 Sep 2022 at 15:37:22 (-0500), 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@arm.com>
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > ---
> >  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);
>
> Why 'int' and not 'bool' here?
>
> IIUC, if you use 'bool' the user can pass any int/0/1/y/n/Y/N, which
> will result in fie_disabled properly having either the value 0 or 1
> (or default FIE_UNSET) if a parameter is not passed.
>
> Then
> 'if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED)'
> can become
> 'if (fie_disabled == FIE_UNSET)' or 'if (fie_disabled < 0)'.
>
> I feel I'm missing something, otherwise you would have done this
> already.
>
> Otherwise FWIW, it looks good to me.
> Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>

Applied as 6.1 material, thanks!

> > +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;
> > --
> > 2.37.1
> >