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amd-pstate preferred core

PATCH Superseded Meng Li 4 participants 16 messages Nov 29, 2023 – Nov 30, 2023

Subsystems (8)
Documentation x86 Kselftest ACPI +4 more subsystems

v11 of 14 Superseded Latest is v14 →

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Meng Li

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#0 lore raw

v11 cover amd-pstate preferred core

Hi all:

The core frequency is subjected to the process variation in semiconductors. Not all cores are able to reach the maximum frequency respecting the infrastructure limits. Consequently, AMD has redefined the concept of maximum frequency of a part. This means that a fraction of cores can reach maximum frequency. To find the best process scheduling policy for a given scenario, OS needs to know the core ordering informed by the platform through highest performance capability register of the CPPC interface.

Earlier implementations of amd-pstate preferred core only support a static core ranking and targeted performance. Now it has the ability to dynamically change the preferred core based on the workload and platform conditions and accounting for thermals and aging.

Amd-pstate driver utilizes the functions and data structures provided by the ITMT architecture to enable the scheduler to favor scheduling on cores which can be get a higher frequency with lower voltage.
We call it amd-pstate preferred core.

Here sched_set_itmt_core_prio() is called to set priorities and sched_set_itmt_support() is called to enable ITMT feature. Amd-pstate driver uses the highest performance value to indicate the priority of CPU. The higher value has a higher priority.

Amd-pstate driver will provide an initial core ordering at boot time. It relies on the CPPC interface to communicate the core ranking to the operating system and scheduler to make sure that OS is choosing the cores with highest performance firstly for scheduling the process. When amd-pstate driver receives a message with the highest performance change, it will update the core ranking.

Changes from V10->V11:
- cpufreq: amd-pstate:
- - according Perry's commnts, I replace the string with str_enabled_disable().

Changes from V9->V10:
- cpufreq: amd-pstate:
- - add judgement for highest_perf. When it is less than 255, the preferred core feature is enabled. And it will set the priority.
- - deleset "static u32 max_highest_perf" etc, because amd p-state perferred coe does not require specail process for hotpulg.

Changes form V8->V9:
- all:
- - pick up Tested-By flag added by Oleksandr.
- cpufreq: amd-pstate:
- - pick up Review-By flag added by Wyes.
- - ignore modification of bug.
- - add a attribute of prefcore_ranking.
- - modify data type conversion from u32 to int.
- Documentation: amd-pstate:
- - pick up Review-By flag added by Wyes.

Changes form V7->V8:
- all:
- - pick up Review-By flag added by Mario and Ray.
- cpufreq: amd-pstate:
- - use hw_prefcore embeds into cpudata structure.
- - delete preferred core init from cpu online/off.

Changes form V6->V7:
- x86:
- - Modify kconfig about X86_AMD_PSTATE.
- cpufreq: amd-pstate:
- - modify incorrect comments about scheduler_work().
- - convert highest_perf data type.
- - modify preferred core init when cpu init and online.
- acpi: cppc:
- - modify link of CPPC highest performance.
- cpufreq:
- - modify link of CPPC highest performance changed.

Changes form V5->V6:
- cpufreq: amd-pstate:
- - modify the wrong tag order.
- - modify warning about hw_prefcore sysfs attribute.
- - delete duplicate comments.
- - modify the variable name cppc_highest_perf to prefcore_ranking.
- - modify judgment conditions for setting highest_perf.
- - modify sysfs attribute for CPPC highest perf to pr_debug message.
- Documentation: amd-pstate:
- - modify warning: title underline too short.

Changes form V4->V5:
- cpufreq: amd-pstate:
- - modify sysfs attribute for CPPC highest perf.
- - modify warning about comments
- - rebase linux-next
- cpufreq:
- - Moidfy warning about function declarations.
- Documentation: amd-pstate:
- - align with ``amd-pstat``

Changes form V3->V4:
- Documentation: amd-pstate:
- - Modify inappropriate descriptions.

Changes form V2->V3:
- x86:
- - Modify kconfig and description.
- cpufreq: amd-pstate:
- - Add Co-developed-by tag in commit message.
- cpufreq:
- - Modify commit message.
- Documentation: amd-pstate:
- - Modify inappropriate descriptions.

Changes form V1->V2:
- acpi: cppc:
- - Add reference link.
- cpufreq:
- - Moidfy link error.
- cpufreq: amd-pstate:
- - Init the priorities of all online CPUs
- - Use a single variable to represent the status of preferred core.
- Documentation:
- - Default enabled preferred core.
- Documentation: amd-pstate:
- - Modify inappropriate descriptions.
- - Default enabled preferred core.
- - Use a single variable to represent the status of preferred core.

Meng Li (7):
x86: Drop CPU_SUP_INTEL from SCHED_MC_PRIO for the expansion.
acpi: cppc: Add get the highest performance cppc control
cpufreq: amd-pstate: Enable amd-pstate preferred core supporting.
cpufreq: Add a notification message that the highest perf has changed
cpufreq: amd-pstate: Update amd-pstate preferred core ranking
dynamically
Documentation: amd-pstate: introduce amd-pstate preferred core
Documentation: introduce amd-pstate preferrd core mode kernel command
line options

 .../admin-guide/kernel-parameters.txt         |   5 +
 Documentation/admin-guide/pm/amd-pstate.rst   |  59 +++++-
 arch/x86/Kconfig                              |   5 +-
 drivers/acpi/cppc_acpi.c                      |  13 ++
 drivers/acpi/processor_driver.c               |   6 +
 drivers/cpufreq/amd-pstate.c                  | 187 ++++++++++++++++--
 drivers/cpufreq/cpufreq.c                     |  13 ++
 include/acpi/cppc_acpi.h                      |   5 +
 include/linux/amd-pstate.h                    |  10 +
 include/linux/cpufreq.h                       |   5 +
 10 files changed, 288 insertions(+), 20 deletions(-)
Signature · 1 line
2.34.1
author
#1 lore raw

PATCH v11 1/7 x86: Drop CPU_SUP_INTEL from SCHED_MC_PRIO for the expansion.

amd-pstate driver also uses SCHED_MC_PRIO, so decouple the requirement of CPU_SUP_INTEL from the dependencies to allow compilation in kernels without Intel CPU support.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 arch/x86/Kconfig | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
arch/x86/Kconfig +3 -2
index ad478a2b49e2..77b1af90f7a2 100644
@@ -1054,8 +1054,9 @@ config SCHED_MC
 
 config SCHED_MC_PRIO
 	bool "CPU core priorities scheduler support"
-	depends on SCHED_MC && CPU_SUP_INTEL
-	select X86_INTEL_PSTATE
+	depends on SCHED_MC
+	select X86_INTEL_PSTATE if CPU_SUP_INTEL
+	select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI
 	select CPU_FREQ
 	default y
 	help
Signature · 1 line
2.34.1
reviewer Reviewed-by on v11 1/7
#2 lore raw

RE: [PATCH V11 1/7] x86: Drop CPU_SUP_INTEL from SCHED_MC_PRIO for the expansion.

[AMD Official Use Only - General]

Quoted 47 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>
Subject: [PATCH V11 1/7] x86: Drop CPU_SUP_INTEL from SCHED_MC_PRIO for the expansion.

amd-pstate driver also uses SCHED_MC_PRIO, so decouple the requirement of CPU_SUP_INTEL from the dependencies to allow compilation in kernels without Intel CPU support.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 arch/x86/Kconfig | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
arch/x86/Kconfig index renamed from arch/x86/Kconfig +0 -0

ad478a2b49e2..77b1af90f7a2 100644

arch/x86/Kconfig +3 -3
@@ -1054,8 +1054,9 @@ config SCHED_MC
 
 config SCHED_MC_PRIO
      bool "CPU core priorities scheduler support"
-     depends on SCHED_MC && CPU_SUP_INTEL
-     select X86_INTEL_PSTATE
+     depends on SCHED_MC
+     select X86_INTEL_PSTATE if CPU_SUP_INTEL
+     select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI
      select CPU_FREQ
      default y
      help
--
Quoted 1 line

2.34.1

Reviewed-by Perry Yuan <[email protected] >
author
#3 lore raw

PATCH v11 2/7 acpi: cppc: Add get the highest performance cppc control

In reply to Meng Li

Add support for getting the highest performance to the generic CPPC driver. This enables downstream drivers such as amd-pstate to discover and use these values.

Please refer to the ACPI_Spec for details on continuous performance control of CPPC.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Acked-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
Link https://uefi.org/specs/ACPI/6.5/08_Processor_Configuration_and_Control.html?highlight=cppc#highest-performance
---
 drivers/acpi/cppc_acpi.c | 13 +++++++++++++
 include/acpi/cppc_acpi.h |  5 +++++
 2 files changed, 18 insertions(+)
drivers/acpi/cppc_acpi.c +13 -0
index 7ff269a78c20..ad388a0e8484 100644
@@ -1154,6 +1154,19 @@ int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf)
 	return cppc_get_perf(cpunum, NOMINAL_PERF, nominal_perf);
 }
 
+/**
+ * cppc_get_highest_perf - Get the highest performance register value.
+ * @cpunum: CPU from which to get highest performance.
+ * @highest_perf: Return address.
+ *
+ * Return: 0 for success, -EIO otherwise.
+ */
+int cppc_get_highest_perf(int cpunum, u64 *highest_perf)
+{
+	return cppc_get_perf(cpunum, HIGHEST_PERF, highest_perf);
+}
+EXPORT_SYMBOL_GPL(cppc_get_highest_perf);
+
 /**
  * cppc_get_epp_perf - Get the epp register value.
  * @cpunum: CPU from which to get epp preference value.
include/acpi/cppc_acpi.h +5 -0
index 6126c977ece0..c0b69ffe7bdb 100644
@@ -139,6 +139,7 @@ struct cppc_cpudata {
 #ifdef CONFIG_ACPI_CPPC_LIB
 extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf);
 extern int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf);
+extern int cppc_get_highest_perf(int cpunum, u64 *highest_perf);
 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);

@@ -165,6 +166,10 @@ static inline int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf)
 {
 	return -ENOTSUPP;
 }
+static inline int cppc_get_highest_perf(int cpunum, u64 *highest_perf)
+{
+	return -ENOTSUPP;
+}
 static inline int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 {
 	return -ENOTSUPP;
Signature · 1 line
2.34.1
reviewer Reviewed-by on v11 2/7
#4 lore raw

RE: [PATCH V11 2/7] acpi: cppc: Add get the highest performance cppc control

[AMD Official Use Only - General]

Quoted 81 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>; Karny, Wyes <[email protected]>
Subject: [PATCH V11 2/7] acpi: cppc: Add get the highest performance cppc control

Add support for getting the highest performance to the generic CPPC driver. This enables downstream drivers such as amd-pstate to discover and use these values.

Please refer to the ACPI_Spec for details on continuous performance control of CPPC.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Acked-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>

Link:
https://uefi.org/specs/ACPI/6.5/08_Processor_Configuration_and_Control.html?
highlight=cppc#highest-performance

---
 drivers/acpi/cppc_acpi.c | 13 +++++++++++++  include/acpi/cppc_acpi.h |  5
+++++
 2 files changed, 18 insertions(+)
drivers/acpi/cppc_acpi.c index renamed from drivers/acpi/cppc_acpi.c +0 -0

7ff269a78c20..ad388a0e8484 100644

drivers/acpi/cppc_acpi.c +11 -0
@@ -1154,6 +1154,19 @@ int cppc_get_nominal_perf(int cpunum, u64
 *nominal_perf)
      return cppc_get_perf(cpunum, NOMINAL_PERF, nominal_perf);  }
 
+/**
+ * cppc_get_highest_perf - Get the highest performance register value.
+ * @cpunum: CPU from which to get highest performance.
+ * @highest_perf: Return address.
+ *
+ * Return: 0 for success, -EIO otherwise.
+ */
+int cppc_get_highest_perf(int cpunum, u64 *highest_perf) {
+     return cppc_get_perf(cpunum, HIGHEST_PERF, highest_perf); }
+EXPORT_SYMBOL_GPL(cppc_get_highest_perf);
+
 /**
  * cppc_get_epp_perf - Get the epp register value.
  * @cpunum: CPU from which to get epp preference value.
include/acpi/cppc_acpi.h index renamed from include/acpi/cppc_acpi.h +0 -0

6126c977ece0..c0b69ffe7bdb 100644

include/acpi/cppc_acpi.h +0 -0
@@ -139,6 +139,7 @@ struct cppc_cpudata {  #ifdef CONFIG_ACPI_CPPC_LIB

extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf); extern int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf);
+extern int cppc_get_highest_perf(int cpunum, u64 *highest_perf);
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); @@ -165,6 +166,10 @@ static inline int

cppc_get_nominal_perf(int cpunum, u64 *nominal_perf)  {
      return -ENOTSUPP;

}

include/acpi/cppc_acpi.h +4 -0
+static inline int cppc_get_highest_perf(int cpunum, u64 *highest_perf)
+{
+     return -ENOTSUPP;
+}
 static inline int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs

*perf_fb_ctrs)  {
      return -ENOTSUPP;
Quoted 2 lines

--
2.34.1

Reviewed-by Perry Yuan <[email protected]>
author
#5 lore raw

PATCH v11 3/7 cpufreq: amd-pstate: Enable amd-pstate preferred core supporting.

In reply to Meng Li

amd-pstate driver utilizes the functions and data structures provided by the ITMT architecture to enable the scheduler to favor scheduling on cores which can be get a higher frequency with lower voltage. We call it amd-pstate preferrred core.

Here sched_set_itmt_core_prio() is called to set priorities and sched_set_itmt_support() is called to enable ITMT feature. amd-pstate driver uses the highest performance value to indicate the priority of CPU. The higher value has a higher priority.

The initial core rankings are set up by amd-pstate when the system boots.

Add a variable hw_prefcore in cpudata structure. It will check if the processor and power firmware support preferred core feature.

Add one new early parameter disable to allow user to disable the preferred core.

Only when hardware supports preferred core and user set enabled in early parameter, amd pstate driver supports preferred core featue.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Co-developed-by Perry Yuan <[email protected]>
Signed-off-by Perry Yuan <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 drivers/cpufreq/amd-pstate.c | 141 +++++++++++++++++++++++++++++++----
 include/linux/amd-pstate.h   |   4 +
 2 files changed, 129 insertions(+), 16 deletions(-)
drivers/cpufreq/amd-pstate.c +125 -16
index 9a1e194d5cf8..74dcf63d75f9 100644
@@ -37,6 +37,7 @@
 #include <linux/uaccess.h>
 #include <linux/static_call.h>
 #include <linux/amd-pstate.h>
+#include <linux/topology.h>
 
 #include <acpi/processor.h>
 #include <acpi/cppc_acpi.h>

@@ -49,6 +50,7 @@
 
 #define AMD_PSTATE_TRANSITION_LATENCY	20000
 #define AMD_PSTATE_TRANSITION_DELAY	1000
+#define AMD_PSTATE_PREFCORE_THRESHOLD	166
 
 /*
  * TODO: We need more time to fine tune processors with shared memory solution

@@ -64,6 +66,7 @@ static struct cpufreq_driver amd_pstate_driver;
 static struct cpufreq_driver amd_pstate_epp_driver;
 static int cppc_state = AMD_PSTATE_UNDEFINED;
 static bool cppc_enabled;
+static bool amd_pstate_prefcore = true;
 
 /*
  * AMD Energy Preference Performance (EPP)

@@ -290,23 +293,21 @@ static inline int amd_pstate_enable(bool enable)
 static int pstate_init_perf(struct amd_cpudata *cpudata)
 {
 	u64 cap1;
-	u32 highest_perf;
 
 	int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
 				     &cap1);
 	if (ret)
 		return ret;
 
-	/*
-	 * TODO: Introduce AMD specific power feature.
-	 *
-	 * CPPC entry doesn't indicate the highest performance in some ASICs.
+	/* For platforms that do not support the preferred core feature, the
+	 * highest_pef may be configured with 166 or 255, to avoid max frequency
+	 * calculated wrongly. we take the AMD_CPPC_HIGHEST_PERF(cap1) value as
+	 * the default max perf.
 	 */
-	highest_perf = amd_get_highest_perf();
-	if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
-		highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
-
-	WRITE_ONCE(cpudata->highest_perf, highest_perf);
+	if (cpudata->hw_prefcore)
+		WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);
+	else
+		WRITE_ONCE(cpudata->highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
 
 	WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
 	WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));

@@ -318,17 +319,15 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
 static int cppc_init_perf(struct amd_cpudata *cpudata)
 {
 	struct cppc_perf_caps cppc_perf;
-	u32 highest_perf;
 
 	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
 	if (ret)
 		return ret;
 
-	highest_perf = amd_get_highest_perf();
-	if (highest_perf > cppc_perf.highest_perf)
-		highest_perf = cppc_perf.highest_perf;
-
-	WRITE_ONCE(cpudata->highest_perf, highest_perf);
+	if (cpudata->hw_prefcore)
+		WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);
+	else
+		WRITE_ONCE(cpudata->highest_perf, cppc_perf.highest_perf);
 
 	WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
 	WRITE_ONCE(cpudata->lowest_nonlinear_perf,

@@ -676,6 +675,80 @@ static void amd_perf_ctl_reset(unsigned int cpu)
 	wrmsrl_on_cpu(cpu, MSR_AMD_PERF_CTL, 0);
 }
 
+/*
+ * Set amd-pstate preferred core enable can't be done directly from cpufreq callbacks
+ * due to locking, so queue the work for later.
+ */
+static void amd_pstste_sched_prefcore_workfn(struct work_struct *work)
+{
+	sched_set_itmt_support();
+}
+static DECLARE_WORK(sched_prefcore_work, amd_pstste_sched_prefcore_workfn);
+
+/*
+ * Get the highest performance register value.
+ * @cpu: CPU from which to get highest performance.
+ * @highest_perf: Return address.
+ *
+ * Return: 0 for success, -EIO otherwise.
+ */
+static int amd_pstate_get_highest_perf(int cpu, u32 *highest_perf)
+{
+	int ret;
+
+	if (boot_cpu_has(X86_FEATURE_CPPC)) {
+		u64 cap1;
+
+		ret = rdmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_CAP1, &cap1);
+		if (ret)
+			return ret;
+		WRITE_ONCE(*highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
+	} else {
+		u64 cppc_highest_perf;
+
+		ret = cppc_get_highest_perf(cpu, &cppc_highest_perf);
+		if (ret)
+			return ret;
+		WRITE_ONCE(*highest_perf, cppc_highest_perf);
+	}
+
+	return (ret);
+}
+
+#define CPPC_MAX_PERF	U8_MAX
+
+static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
+{
+	int ret, prio;
+	u32 highest_perf;
+
+	ret = amd_pstate_get_highest_perf(cpudata->cpu, &highest_perf);
+	if (ret)
+		return;
+
+	cpudata->hw_prefcore = true;
+	/* check if CPPC preferred core feature is enabled*/
+	if (highest_perf < CPPC_MAX_PERF)
+		prio = (int)highest_perf;
+	else {
+		pr_debug("AMD CPPC preferred core is unsupported!\n");
+		cpudata->hw_prefcore = false;
+		return;
+	}
+
+	if (!amd_pstate_prefcore)
+		return;
+
+	/*
+	 * The priorities can be set regardless of whether or not
+	 * sched_set_itmt_support(true) has been called and it is valid to
+	 * update them at any time after it has been called.
+	 */
+	sched_set_itmt_core_prio(prio, cpudata->cpu);
+
+	schedule_work(&sched_prefcore_work);
+}
+
 static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
 {
 	int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;

@@ -697,6 +770,8 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
 
 	cpudata->cpu = policy->cpu;
 
+	amd_pstate_init_prefcore(cpudata);
+
 	ret = amd_pstate_init_perf(cpudata);
 	if (ret)
 		goto free_cpudata1;

@@ -845,6 +920,17 @@ static ssize_t show_amd_pstate_highest_perf(struct cpufreq_policy *policy,
 	return sysfs_emit(buf, "%u\n", perf);
 }
 
+static ssize_t show_amd_pstate_hw_prefcore(struct cpufreq_policy *policy,
+					   char *buf)
+{
+	bool hw_prefcore;
+	struct amd_cpudata *cpudata = policy->driver_data;
+
+	hw_prefcore = READ_ONCE(cpudata->hw_prefcore);
+
+	return sysfs_emit(buf, "%s\n", str_enabled_disabled(hw_prefcore));
+}
+
 static ssize_t show_energy_performance_available_preferences(
 				struct cpufreq_policy *policy, char *buf)
 {

@@ -1037,18 +1123,27 @@ static ssize_t status_store(struct device *a, struct device_attribute *b,
 	return ret < 0 ? ret : count;
 }
 
+static ssize_t prefcore_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", str_enabled_disabled(amd_pstate_prefcore));
+}
+
 cpufreq_freq_attr_ro(amd_pstate_max_freq);
 cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
 
 cpufreq_freq_attr_ro(amd_pstate_highest_perf);
+cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
 cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);
 static DEVICE_ATTR_RW(status);
+static DEVICE_ATTR_RO(prefcore);
 
 static struct freq_attr *amd_pstate_attr[] = {
 	&amd_pstate_max_freq,
 	&amd_pstate_lowest_nonlinear_freq,
 	&amd_pstate_highest_perf,
+	&amd_pstate_hw_prefcore,
 	NULL,
 };
 

@@ -1056,6 +1151,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 	&amd_pstate_max_freq,
 	&amd_pstate_lowest_nonlinear_freq,
 	&amd_pstate_highest_perf,
+	&amd_pstate_hw_prefcore,
 	&energy_performance_preference,
 	&energy_performance_available_preferences,
 	NULL,

@@ -1063,6 +1159,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 
 static struct attribute *pstate_global_attributes[] = {
 	&dev_attr_status.attr,
+	&dev_attr_prefcore.attr,
 	NULL
 };
 

@@ -1114,6 +1211,8 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	cpudata->cpu = policy->cpu;
 	cpudata->epp_policy = 0;
 
+	amd_pstate_init_prefcore(cpudata);
+
 	ret = amd_pstate_init_perf(cpudata);
 	if (ret)
 		goto free_cpudata1;

@@ -1527,7 +1626,17 @@ static int __init amd_pstate_param(char *str)
 
 	return amd_pstate_set_driver(mode_idx);
 }
+
+static int __init amd_prefcore_param(char *str)
+{
+	if (!strcmp(str, "disable"))
+		amd_pstate_prefcore = false;
+
+	return 0;
+}
+
 early_param("amd_pstate", amd_pstate_param);
+early_param("amd_prefcore", amd_prefcore_param);
 
 MODULE_AUTHOR("Huang Rui <[email protected]>");
 MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");
include/linux/amd-pstate.h +4 -0
index 446394f84606..87e140e9e6db 100644
@@ -52,6 +52,9 @@ struct amd_aperf_mperf {
  * @prev: Last Aperf/Mperf/tsc count value read from register
  * @freq: current cpu frequency value
  * @boost_supported: check whether the Processor or SBIOS supports boost mode
+ * @hw_prefcore: check whether HW supports preferred core featue.
+ * 		  Only when hw_prefcore and early prefcore param are true,
+ * 		  AMD P-State driver supports preferred core featue.
  * @epp_policy: Last saved policy used to set energy-performance preference
  * @epp_cached: Cached CPPC energy-performance preference value
  * @policy: Cpufreq policy value

@@ -81,6 +84,7 @@ struct amd_cpudata {
 
 	u64	freq;
 	bool	boost_supported;
+	bool	hw_prefcore;
 
 	/* EPP feature related attributes*/
 	s16	epp_policy;
Signature · 1 line
2.34.1
author
#6 lore raw

PATCH v11 4/7 cpufreq: Add a notification message that the highest perf has changed

In reply to Meng Li

ACPI 6.5 section 8.4.6.1.1.1 specifies that Notify event 0x85 can be emmitted to cause the the OSPM to re-evaluate the highest performance register. Add support for this event.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
Link https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#processor-device-notification-values
---
 drivers/acpi/processor_driver.c |  6 ++++++
 drivers/cpufreq/cpufreq.c       | 13 +++++++++++++
 include/linux/cpufreq.h         |  5 +++++
 3 files changed, 24 insertions(+)
drivers/acpi/processor_driver.c +6 -0
index 4bd16b3f0781..29b2fb68a35d 100644
@@ -27,6 +27,7 @@
 #define ACPI_PROCESSOR_NOTIFY_PERFORMANCE 0x80
 #define ACPI_PROCESSOR_NOTIFY_POWER	0x81
 #define ACPI_PROCESSOR_NOTIFY_THROTTLING	0x82
+#define ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED	0x85
 
 MODULE_AUTHOR("Paul Diefenbaugh");
 MODULE_DESCRIPTION("ACPI Processor Driver");

@@ -83,6 +84,11 @@ static void acpi_processor_notify(acpi_handle handle, u32 event, void *data)
 		acpi_bus_generate_netlink_event(device->pnp.device_class,
 						  dev_name(&device->dev), event, 0);
 		break;
+	case ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED:
+		cpufreq_update_highest_perf(pr->id);
+		acpi_bus_generate_netlink_event(device->pnp.device_class,
+						  dev_name(&device->dev), event, 0);
+		break;
 	default:
 		acpi_handle_debug(handle, "Unsupported event [0x%x]\n", event);
 		break;
drivers/cpufreq/cpufreq.c +13 -0
index 934d35f570b7..14a4cbc6dd05 100644
@@ -2717,6 +2717,19 @@ void cpufreq_update_limits(unsigned int cpu)
 }
 EXPORT_SYMBOL_GPL(cpufreq_update_limits);
 
+/**
+ * cpufreq_update_highest_perf - Update highest performance for a given CPU.
+ * @cpu: CPU to update the highest performance for.
+ *
+ * Invoke the driver's ->update_highest_perf callback if present
+ */
+void cpufreq_update_highest_perf(unsigned int cpu)
+{
+	if (cpufreq_driver->update_highest_perf)
+		cpufreq_driver->update_highest_perf(cpu);
+}
+EXPORT_SYMBOL_GPL(cpufreq_update_highest_perf);
+
 /*********************************************************************
  *               BOOST						     *
  *********************************************************************/
include/linux/cpufreq.h +5 -0
index 1c5ca92a0555..f62257b2a42f 100644
@@ -235,6 +235,7 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu);
 void refresh_frequency_limits(struct cpufreq_policy *policy);
 void cpufreq_update_policy(unsigned int cpu);
 void cpufreq_update_limits(unsigned int cpu);
+void cpufreq_update_highest_perf(unsigned int cpu);
 bool have_governor_per_policy(void);
 bool cpufreq_supports_freq_invariance(void);
 struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);

@@ -263,6 +264,7 @@ static inline bool cpufreq_supports_freq_invariance(void)
 	return false;
 }
 static inline void disable_cpufreq(void) { }
+static inline void cpufreq_update_highest_perf(unsigned int cpu) { }
 #endif
 
 #ifdef CONFIG_CPU_FREQ_STAT

@@ -380,6 +382,9 @@ struct cpufreq_driver {
 	/* Called to update policy limits on firmware notifications. */
 	void		(*update_limits)(unsigned int cpu);
 
+	/* Called to update highest performance on firmware notifications. */
+	void		(*update_highest_perf)(unsigned int cpu);
+
 	/* optional */
 	int		(*bios_limit)(int cpu, unsigned int *limit);
Signature · 1 line
2.34.1
reviewer Reviewed-by on v11 4/7
#7 lore raw

RE: [PATCH V11 4/7] cpufreq: Add a notification message that the highest perf has changed

[AMD Official Use Only - General]

Quoted 120 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>
Subject: [PATCH V11 4/7] cpufreq: Add a notification message that the highest perf has changed

ACPI 6.5 section 8.4.6.1.1.1 specifies that Notify event 0x85 can be emmitted to cause the the OSPM to re-evaluate the highest performance register. Add support for this event.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>

Link:
https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.ht
ml#processor-device-notification-values

---
 drivers/acpi/processor_driver.c |  6 ++++++
 drivers/cpufreq/cpufreq.c       | 13 +++++++++++++
 include/linux/cpufreq.h         |  5 +++++
 3 files changed, 24 insertions(+)
drivers/acpi/processor_driver.c +1 -0
index 4bd16b3f0781..29b2fb68a35d 100644
@@ -27,6 +27,7 @@
 #define ACPI_PROCESSOR_NOTIFY_PERFORMANCE 0x80
 #define ACPI_PROCESSOR_NOTIFY_POWER  0x81
 #define ACPI_PROCESSOR_NOTIFY_THROTTLING     0x82
+#define ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED    0x85
 
 MODULE_AUTHOR("Paul Diefenbaugh");
 MODULE_DESCRIPTION("ACPI Processor Driver"); @@ -83,6 +84,11 @@

static void acpi_processor_notify(acpi_handle handle, u32 event, void *data)

              acpi_bus_generate_netlink_event(device->pnp.device_class,
                                                dev_name(&device->dev),
event, 0);
              break;
drivers/acpi/processor_driver.c +4 -0
+     case ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED:
+             cpufreq_update_highest_perf(pr->id);
+             acpi_bus_generate_netlink_event(device->pnp.device_class,
+                                               dev_name(&device->dev),

event, 0);

+             break;
      default:
              acpi_handle_debug(handle, "Unsupported event [0x%x]\n",
event);
              break;
drivers/cpufreq/cpufreq.c index renamed from drivers/cpufreq/cpufreq.c +0 -0

934d35f570b7..14a4cbc6dd05 100644

drivers/cpufreq/cpufreq.c +2 -0
@@ -2717,6 +2717,19 @@ void cpufreq_update_limits(unsigned int cpu)  }
 EXPORT_SYMBOL_GPL(cpufreq_update_limits);
 
+/**
+ * cpufreq_update_highest_perf - Update highest performance for a given

CPU.
+ * @cpu: CPU to update the highest performance for.
+ *
+ * Invoke the driver's ->update_highest_perf callback if present */

drivers/cpufreq/cpufreq.c +6 -0
+void cpufreq_update_highest_perf(unsigned int cpu) {
+     if (cpufreq_driver->update_highest_perf)
+             cpufreq_driver->update_highest_perf(cpu);
+}
+EXPORT_SYMBOL_GPL(cpufreq_update_highest_perf);
+

/******************************************************************
***
* BOOST *

*******************************************************************
**/

include/linux/cpufreq.h index renamed from include/linux/cpufreq.h +0 -0

1c5ca92a0555..f62257b2a42f 100644

include/linux/cpufreq.h +0 -0
@@ -235,6 +235,7 @@ int cpufreq_get_policy(struct cpufreq_policy *policy,

unsigned int cpu); void refresh_frequency_limits(struct cpufreq_policy *policy); void cpufreq_update_policy(unsigned int cpu); void cpufreq_update_limits(unsigned int cpu);

include/linux/cpufreq.h +2 -0
+void cpufreq_update_highest_perf(unsigned int cpu);
 bool have_governor_per_policy(void);
 bool cpufreq_supports_freq_invariance(void);
 struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);

@@ -263,6 +264,7 @@ static inline bool
 cpufreq_supports_freq_invariance(void)
      return false;
 }
 static inline void disable_cpufreq(void) { }
+static inline void cpufreq_update_highest_perf(unsigned int cpu) { }
 #endif

#ifdef CONFIG_CPU_FREQ_STAT

include/linux/cpufreq.h +3 -1
@@ -380,6 +382,9 @@ struct cpufreq_driver {
      /* Called to update policy limits on firmware notifications. */
      void            (*update_limits)(unsigned int cpu);
 
+     /* Called to update highest performance on firmware notifications. */
+     void            (*update_highest_perf)(unsigned int cpu);
+
      /* optional */
      int             (*bios_limit)(int cpu, unsigned int *limit);
 
--
Quoted 1 line

2.34.1

Reviewed-by Perry Yuan <[email protected]>
author
#8 lore raw

PATCH v11 5/7 cpufreq: amd-pstate: Update amd-pstate preferred core ranking dynamically

In reply to Meng Li

Preferred core rankings can be changed dynamically by the platform based on the workload and platform conditions and accounting for thermals and aging.
When this occurs, cpu priority need to be set.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 drivers/cpufreq/amd-pstate.c | 46 ++++++++++++++++++++++++++++++++++++
 include/linux/amd-pstate.h   |  6 +++++
 2 files changed, 52 insertions(+)
drivers/cpufreq/amd-pstate.c +46 -0
index 74dcf63d75f9..88df6510dcc0 100644
@@ -312,6 +312,7 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
 	WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
 	WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));
 	WRITE_ONCE(cpudata->lowest_perf, AMD_CPPC_LOWEST_PERF(cap1));
+	WRITE_ONCE(cpudata->prefcore_ranking, AMD_CPPC_HIGHEST_PERF(cap1));
 
 	return 0;
 }

@@ -333,6 +334,7 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
 	WRITE_ONCE(cpudata->lowest_nonlinear_perf,
 		   cppc_perf.lowest_nonlinear_perf);
 	WRITE_ONCE(cpudata->lowest_perf, cppc_perf.lowest_perf);
+	WRITE_ONCE(cpudata->prefcore_ranking, cppc_perf.highest_perf);
 
 	if (cppc_state == AMD_PSTATE_ACTIVE)
 		return 0;

@@ -749,6 +751,34 @@ static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
 	schedule_work(&sched_prefcore_work);
 }
 
+static void amd_pstate_update_highest_perf(unsigned int cpu)
+{
+	struct cpufreq_policy *policy;
+	struct amd_cpudata *cpudata;
+	u32 prev_high = 0, cur_high = 0;
+	int ret;
+
+	if ((!amd_pstate_prefcore) || (!cpudata->hw_prefcore))
+		return;
+
+	ret = amd_pstate_get_highest_perf(cpu, &cur_high);
+	if (ret)
+		return;
+
+	policy = cpufreq_cpu_get(cpu);
+	cpudata = policy->driver_data;
+	prev_high = READ_ONCE(cpudata->prefcore_ranking);
+
+	if (prev_high != cur_high) {
+		WRITE_ONCE(cpudata->prefcore_ranking, cur_high);
+
+		if (cur_high < CPPC_MAX_PERF)
+			sched_set_itmt_core_prio((int)cur_high, cpu);
+	}
+
+	cpufreq_cpu_put(policy);
+}
+
 static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
 {
 	int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;

@@ -920,6 +950,17 @@ static ssize_t show_amd_pstate_highest_perf(struct cpufreq_policy *policy,
 	return sysfs_emit(buf, "%u\n", perf);
 }
 
+static ssize_t show_amd_pstate_prefcore_ranking(struct cpufreq_policy *policy,
+						char *buf)
+{
+	u32 perf;
+	struct amd_cpudata *cpudata = policy->driver_data;
+
+	perf = READ_ONCE(cpudata->prefcore_ranking);
+
+	return sysfs_emit(buf, "%u\n", perf);
+}
+
 static ssize_t show_amd_pstate_hw_prefcore(struct cpufreq_policy *policy,
 					   char *buf)
 {

@@ -1133,6 +1174,7 @@ cpufreq_freq_attr_ro(amd_pstate_max_freq);
 cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
 
 cpufreq_freq_attr_ro(amd_pstate_highest_perf);
+cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
 cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
 cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);

@@ -1143,6 +1185,7 @@ static struct freq_attr *amd_pstate_attr[] = {
 	&amd_pstate_max_freq,
 	&amd_pstate_lowest_nonlinear_freq,
 	&amd_pstate_highest_perf,
+	&amd_pstate_prefcore_ranking,
 	&amd_pstate_hw_prefcore,
 	NULL,
 };

@@ -1151,6 +1194,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 	&amd_pstate_max_freq,
 	&amd_pstate_lowest_nonlinear_freq,
 	&amd_pstate_highest_perf,
+	&amd_pstate_prefcore_ranking,
 	&amd_pstate_hw_prefcore,
 	&energy_performance_preference,
 	&energy_performance_available_preferences,

@@ -1491,6 +1535,7 @@ static struct cpufreq_driver amd_pstate_driver = {
 	.suspend	= amd_pstate_cpu_suspend,
 	.resume		= amd_pstate_cpu_resume,
 	.set_boost	= amd_pstate_set_boost,
+	.update_highest_perf	= amd_pstate_update_highest_perf,
 	.name		= "amd-pstate",
 	.attr		= amd_pstate_attr,
 };

@@ -1505,6 +1550,7 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
 	.online		= amd_pstate_epp_cpu_online,
 	.suspend	= amd_pstate_epp_suspend,
 	.resume		= amd_pstate_epp_resume,
+	.update_highest_perf	= amd_pstate_update_highest_perf,
 	.name		= "amd-pstate-epp",
 	.attr		= amd_pstate_epp_attr,
 };
include/linux/amd-pstate.h +6 -0
index 87e140e9e6db..426822612373 100644
@@ -39,11 +39,16 @@ struct amd_aperf_mperf {
  * @cppc_req_cached: cached performance request hints
  * @highest_perf: the maximum performance an individual processor may reach,
  *		  assuming ideal conditions
+ *		  For platforms that do not support the preferred core feature, the
+ *		  highest_pef may be configured with 166 or 255, to avoid max frequency
+ *		  calculated wrongly. we take the fixed value as the highest_perf.
  * @nominal_perf: the maximum sustained performance level of the processor,
  *		  assuming ideal operating conditions
  * @lowest_nonlinear_perf: the lowest performance level at which nonlinear power
  *			   savings are achieved
  * @lowest_perf: the absolute lowest performance level of the processor
+ * @prefcore_ranking: the preferred core ranking, the higher value indicates a higher
+ * 		  priority.
  * @max_freq: the frequency that mapped to highest_perf
  * @min_freq: the frequency that mapped to lowest_perf
  * @nominal_freq: the frequency that mapped to nominal_perf

@@ -73,6 +78,7 @@ struct amd_cpudata {
 	u32	nominal_perf;
 	u32	lowest_nonlinear_perf;
 	u32	lowest_perf;
+	u32     prefcore_ranking;
 
 	u32	max_freq;
 	u32	min_freq;
Signature · 1 line
2.34.1
#9 lore raw

Re: [PATCH V11 5/7] cpufreq: amd-pstate: Update amd-pstate preferred core ranking dynamically

Hi Meng,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Meng-Li/x86-Drop-CPU_SUP_INTEL-from-SCHED_MC_PRIO-for-the-expansion/20231129-160700
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
patch link:    https://lore.kernel.org/r/20231129065437.290183-6-li.meng%40amd.com
patch subject: [PATCH V11 5/7] cpufreq: amd-pstate: Update amd-pstate preferred core ranking dynamically
config: i386-randconfig-141-20231129 (https://download.01.org/0day-ci/archive/20231130/[email protected]/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
reproduce: (https://download.01.org/0day-ci/archive/20231130/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags

| Reported-by: kernel test robot <[email protected]>
| Reported-by: Dan Carpenter <[email protected]>
| Closes: https://lore.kernel.org/r/[email protected]/

smatch warnings:
drivers/cpufreq/amd-pstate.c:763 amd_pstate_update_highest_perf() error: potentially dereferencing uninitialized 'cpudata'.

vim +/cpudata +763 drivers/cpufreq/amd-pstate.c

b631665e8af8a7 Meng Li 2023-11-29  756  static void amd_pstate_update_highest_perf(unsigned int cpu)
b631665e8af8a7 Meng Li 2023-11-29  757  {
b631665e8af8a7 Meng Li 2023-11-29  758  	struct cpufreq_policy *policy;
b631665e8af8a7 Meng Li 2023-11-29  759  	struct amd_cpudata *cpudata;
b631665e8af8a7 Meng Li 2023-11-29  760  	u32 prev_high = 0, cur_high = 0;
b631665e8af8a7 Meng Li 2023-11-29  761  	int ret;
b631665e8af8a7 Meng Li 2023-11-29  762  
b631665e8af8a7 Meng Li 2023-11-29 @763  	if ((!amd_pstate_prefcore) || (!cpudata->hw_prefcore))
                                                                                ^^^^^^^^^^^^^^^^^^^^

Uninitialized.

Normally the Clang devs would be the first to report this but they're sleeping on the ball this time. :P #FRISTPOST #LOL

b631665e8af8a7 Meng Li 2023-11-29  764  		return;
b631665e8af8a7 Meng Li 2023-11-29  765  
b631665e8af8a7 Meng Li 2023-11-29  766  	ret = amd_pstate_get_highest_perf(cpu, &cur_high);
b631665e8af8a7 Meng Li 2023-11-29  767  	if (ret)
b631665e8af8a7 Meng Li 2023-11-29  768  		return;
b631665e8af8a7 Meng Li 2023-11-29  769  
b631665e8af8a7 Meng Li 2023-11-29  770  	policy = cpufreq_cpu_get(cpu);
b631665e8af8a7 Meng Li 2023-11-29  771  	cpudata = policy->driver_data;
b631665e8af8a7 Meng Li 2023-11-29  772  	prev_high = READ_ONCE(cpudata->prefcore_ranking);
b631665e8af8a7 Meng Li 2023-11-29  773  
b631665e8af8a7 Meng Li 2023-11-29  774  	if (prev_high != cur_high) {
b631665e8af8a7 Meng Li 2023-11-29  775  		WRITE_ONCE(cpudata->prefcore_ranking, cur_high);
b631665e8af8a7 Meng Li 2023-11-29  776  
b631665e8af8a7 Meng Li 2023-11-29  777  		if (cur_high < CPPC_MAX_PERF)
b631665e8af8a7 Meng Li 2023-11-29  778  			sched_set_itmt_core_prio((int)cur_high, cpu);
b631665e8af8a7 Meng Li 2023-11-29  779  	}
b631665e8af8a7 Meng Li 2023-11-29  780  
b631665e8af8a7 Meng Li 2023-11-29  781  	cpufreq_cpu_put(policy);
b631665e8af8a7 Meng Li 2023-11-29  782  }
Signature · 2 lines
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
reviewer Reviewed-by on v11 5/7
#10 lore raw

RE: [PATCH V11 5/7] cpufreq: amd-pstate: Update amd-pstate preferred core ranking dynamically

In reply to Meng Li

[AMD Official Use Only - General]

Quoted 187 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>; Karny, Wyes <[email protected]>
Subject: [PATCH V11 5/7] cpufreq: amd-pstate: Update amd-pstate preferred core ranking dynamically

Preferred core rankings can be changed dynamically by the platform based on the workload and platform conditions and accounting for thermals and aging. When this occurs, cpu priority need to be set.

Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 drivers/cpufreq/amd-pstate.c | 46
++++++++++++++++++++++++++++++++++++
 include/linux/amd-pstate.h   |  6 +++++
 2 files changed, 52 insertions(+)
drivers/cpufreq/amd-pstate.c +0 -0
index 74dcf63d75f9..88df6510dcc0 100644
@@ -312,6 +312,7 @@ static int pstate_init_perf(struct amd_cpudata
 *cpudata)
      WRITE_ONCE(cpudata->nominal_perf,
 AMD_CPPC_NOMINAL_PERF(cap1));
      WRITE_ONCE(cpudata->lowest_nonlinear_perf,
 AMD_CPPC_LOWNONLIN_PERF(cap1));
      WRITE_ONCE(cpudata->lowest_perf,

AMD_CPPC_LOWEST_PERF(cap1));
+ WRITE_ONCE(cpudata->prefcore_ranking,
AMD_CPPC_HIGHEST_PERF(cap1));

      return 0;

}

drivers/cpufreq/amd-pstate.c +1 -0
@@ -333,6 +334,7 @@ static int cppc_init_perf(struct amd_cpudata
 *cpudata)
      WRITE_ONCE(cpudata->lowest_nonlinear_perf,
                 cppc_perf.lowest_nonlinear_perf);
      WRITE_ONCE(cpudata->lowest_perf, cppc_perf.lowest_perf);
+     WRITE_ONCE(cpudata->prefcore_ranking, cppc_perf.highest_perf);
 
      if (cppc_state == AMD_PSTATE_ACTIVE)

              return 0;
drivers/cpufreq/amd-pstate.c +38 -0
@@ -749,6 +751,34 @@ static void amd_pstate_init_prefcore(struct
 amd_cpudata *cpudata)
      schedule_work(&sched_prefcore_work);
 }
 
+static void amd_pstate_update_highest_perf(unsigned int cpu) {
+     struct cpufreq_policy *policy;
+     struct amd_cpudata *cpudata;
+     u32 prev_high = 0, cur_high = 0;
+     int ret;
+
+     if ((!amd_pstate_prefcore) || (!cpudata->hw_prefcore))
+             return;
+
+     ret = amd_pstate_get_highest_perf(cpu, &cur_high);
+     if (ret)
+             return;
+
+     policy = cpufreq_cpu_get(cpu);
+     cpudata = policy->driver_data;
+     prev_high = READ_ONCE(cpudata->prefcore_ranking);
+
+     if (prev_high != cur_high) {
+             WRITE_ONCE(cpudata->prefcore_ranking, cur_high);
+
+             if (cur_high < CPPC_MAX_PERF)
+                     sched_set_itmt_core_prio((int)cur_high, cpu);
+     }
+
+     cpufreq_cpu_put(policy);
+}
+
 static int amd_pstate_cpu_init(struct cpufreq_policy *policy)  {
      int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;

@@ -920,6 +950,17 @@ static ssize_t show_amd_pstate_highest_perf(struct
 cpufreq_policy *policy,
      return sysfs_emit(buf, "%u\n", perf);
 }
 
+static ssize_t show_amd_pstate_prefcore_ranking(struct cpufreq_policy
 *policy,
+                                             char *buf)
+{
+     u32 perf;
+     struct amd_cpudata *cpudata = policy->driver_data;
+
+     perf = READ_ONCE(cpudata->prefcore_ranking);
+
+     return sysfs_emit(buf, "%u\n", perf);
+}
+
 static ssize_t show_amd_pstate_hw_prefcore(struct cpufreq_policy *policy,

char *buf)
{

drivers/cpufreq/amd-pstate.c +5 -0
@@ -1133,6 +1174,7 @@ cpufreq_freq_attr_ro(amd_pstate_max_freq);
 cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
 
 cpufreq_freq_attr_ro(amd_pstate_highest_perf);
+cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
 cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
 cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);

@@ -1143,6 +1185,7 @@ static struct freq_attr *amd_pstate_attr[] = {
      &amd_pstate_max_freq,
      &amd_pstate_lowest_nonlinear_freq,
      &amd_pstate_highest_perf,
+     &amd_pstate_prefcore_ranking,
      &amd_pstate_hw_prefcore,
      NULL,
 };

@@ -1151,6 +1194,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
      &amd_pstate_max_freq,
      &amd_pstate_lowest_nonlinear_freq,
      &amd_pstate_highest_perf,
+     &amd_pstate_prefcore_ranking,
      &amd_pstate_hw_prefcore,
      &energy_performance_preference,
      &energy_performance_available_preferences,

@@ -1491,6 +1535,7 @@ static struct cpufreq_driver amd_pstate_driver = {
      .suspend        = amd_pstate_cpu_suspend,
      .resume         = amd_pstate_cpu_resume,
      .set_boost      = amd_pstate_set_boost,
+     .update_highest_perf    = amd_pstate_update_highest_perf,
      .name           = "amd-pstate",
      .attr           = amd_pstate_attr,
 };

@@ -1505,6 +1550,7 @@ static struct cpufreq_driver
 amd_pstate_epp_driver = {
      .online         = amd_pstate_epp_cpu_online,
      .suspend        = amd_pstate_epp_suspend,
      .resume         = amd_pstate_epp_resume,
+     .update_highest_perf    = amd_pstate_update_highest_perf,
      .name           = "amd-pstate-epp",
      .attr           = amd_pstate_epp_attr,

};

include/linux/amd-pstate.h index renamed from include/linux/amd-pstate.h +0 -0

87e140e9e6db..426822612373 100644

include/linux/amd-pstate.h +1 -0
@@ -39,11 +39,16 @@ struct amd_aperf_mperf {
  * @cppc_req_cached: cached performance request hints
  * @highest_perf: the maximum performance an individual processor may
 reach,
  *             assuming ideal conditions
+ *             For platforms that do not support the preferred core feature,

the
+ * highest_pef may be configured with 166 or 255, to avoid
max frequency
+ * calculated wrongly. we take the fixed value as the
highest_perf.
* @nominal_perf: the maximum sustained performance level of the
processor,
* assuming ideal operating conditions
* @lowest_nonlinear_perf: the lowest performance level at which nonlinear
power
* savings are achieved
* @lowest_perf: the absolute lowest performance level of the processor
+ * @prefcore_ranking: the preferred core ranking, the higher value indicates a higher
+ * priority.
* @max_freq: the frequency that mapped to highest_perf
* @min_freq: the frequency that mapped to lowest_perf
* @nominal_freq: the frequency that mapped to nominal_perf @@ -73,6

+78,7 @@ struct amd_cpudata {
      u32     nominal_perf;
      u32     lowest_nonlinear_perf;
      u32     lowest_perf;
Quoted 6 lines

+ u32 prefcore_ranking;

      u32     max_freq;
      u32     min_freq;

--
2.34.1

Reviewed-by Perry Yuan <[email protected]>
author
#11 lore raw

PATCH v11 6/7 Documentation: amd-pstate: introduce amd-pstate preferred core

In reply to Meng Li

Introduce amd-pstate preferred core.

check preferred core state set by the kernel parameter:

$ cat /sys/devices/system/cpu/amd-pstate/prefcore
Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 Documentation/admin-guide/pm/amd-pstate.rst | 59 ++++++++++++++++++++-
 1 file changed, 57 insertions(+), 2 deletions(-)
Documentation/admin-guide/pm/amd-pstate.rst +57 -2
index 1cf40f69278c..0b832ff529db 100644
@@ -300,8 +300,8 @@ platforms. The AMD P-States mechanism is the more performance and energy
 efficiency frequency management method on AMD processors.
 
 
-AMD Pstate Driver Operation Modes
-=================================
+``amd-pstate`` Driver Operation Modes
+======================================
 
 ``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode,
 non-autonomous (passive) mode and guided autonomous (guided) mode.

@@ -353,6 +353,48 @@ is activated.  In this mode, driver requests minimum and maximum performance
 level and the platform autonomously selects a performance level in this range
 and appropriate to the current workload.
 
+``amd-pstate`` Preferred Core
+=================================
+
+The core frequency is subjected to the process variation in semiconductors.
+Not all cores are able to reach the maximum frequency respecting the
+infrastructure limits. Consequently, AMD has redefined the concept of
+maximum frequency of a part. This means that a fraction of cores can reach
+maximum frequency. To find the best process scheduling policy for a given
+scenario, OS needs to know the core ordering informed by the platform through
+highest performance capability register of the CPPC interface.
+
+``amd-pstate`` preferred core enables the scheduler to prefer scheduling on
+cores that can achieve a higher frequency with lower voltage. The preferred
+core rankings can dynamically change based on the workload, platform conditions,
+thermals and ageing.
+
+The priority metric will be initialized by the ``amd-pstate`` driver. The ``amd-pstate``
+driver will also determine whether or not ``amd-pstate`` preferred core is
+supported by the platform.
+
+``amd-pstate`` driver will provide an initial core ordering when the system boots.
+The platform uses the CPPC interfaces to communicate the core ranking to the
+operating system and scheduler to make sure that OS is choosing the cores
+with highest performance firstly for scheduling the process. When ``amd-pstate``
+driver receives a message with the highest performance change, it will
+update the core ranking and set the cpu's priority.
+
+``amd-pstate`` Preferred Core Switch
+=================================
+Kernel Parameters
+-----------------
+
+``amd-pstate`` peferred core`` has two states: enable and disable.
+Enable/disable states can be chosen by different kernel parameters.
+Default enable ``amd-pstate`` preferred core.
+
+``amd_prefcore=disable``
+
+For systems that support ``amd-pstate`` preferred core, the core rankings will
+always be advertised by the platform. But OS can choose to ignore that via the
+kernel parameter ``amd_prefcore=disable``.
+
 User Space Interface in ``sysfs`` - General
 ===========================================
 

@@ -385,6 +427,19 @@ control its functionality at the system level.  They are located in the
         to the operation mode represented by that string - or to be
         unregistered in the "disable" case.
 
+``prefcore``
+	Preferred core state of the driver: "enabled" or "disabled".
+
+	"enabled"
+		Enable the ``amd-pstate`` preferred core.
+
+	"disabled"
+		Disable the ``amd-pstate`` preferred core
+
+
+        This attribute is read-only to check the state of preferred core set
+        by the kernel parameter.
+
 ``cpupower`` tool support for ``amd-pstate``
 ===============================================
Signature · 1 line
2.34.1
reviewer Reviewed-by on v11 6/7
#12 lore raw

RE: [PATCH V11 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core

[AMD Official Use Only - General]

Quoted 123 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>; Karny, Wyes <[email protected]>
Subject: [PATCH V11 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core

Introduce amd-pstate preferred core.

check preferred core state set by the kernel parameter:

$ cat /sys/devices/system/cpu/amd-pstate/prefcore
Tested-by Oleksandr Natalenko <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Signed-off-by Meng Li <[email protected]>
---
 Documentation/admin-guide/pm/amd-pstate.rst | 59
++++++++++++++++++++-
 1 file changed, 57 insertions(+), 2 deletions(-)
Documentation/admin-guide/pm/amd-pstate.rst +0 -0
index 1cf40f69278c..0b832ff529db 100644
@@ -300,8 +300,8 @@ platforms. The AMD P-States mechanism is the more

performance and energy efficiency frequency management method on AMD processors.

-AMD Pstate Driver Operation Modes
-=================================
+``amd-pstate`` Driver Operation Modes
+======================================

``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode,
non-autonomous (passive) mode and guided autonomous (guided) mode.

Documentation/admin-guide/pm/amd-pstate.rst +0 -0
@@ -353,6 +353,48 @@ is activated.  In this mode, driver requests minimum

and maximum performance level and the platform autonomously selects a performance level in this range and appropriate to the current workload.

+``amd-pstate`` Preferred Core
+=================================

Documentation/admin-guide/pm/amd-pstate.rst +8 -0
+
+The core frequency is subjected to the process variation in semiconductors.
+Not all cores are able to reach the maximum frequency respecting the
+infrastructure limits. Consequently, AMD has redefined the concept of
+maximum frequency of a part. This means that a fraction of cores can
+reach maximum frequency. To find the best process scheduling policy for
+a given scenario, OS needs to know the core ordering informed by the
+platform through highest performance capability register of the CPPC

interface.

Documentation/admin-guide/pm/amd-pstate.rst +11 -0
+
+``amd-pstate`` preferred core enables the scheduler to prefer
+scheduling on cores that can achieve a higher frequency with lower
+voltage. The preferred core rankings can dynamically change based on
+the workload, platform conditions, thermals and ageing.
+
+The priority metric will be initialized by the ``amd-pstate`` driver.
+The ``amd-pstate`` driver will also determine whether or not
+``amd-pstate`` preferred core is supported by the platform.
+
+``amd-pstate`` driver will provide an initial core ordering when the system

boots.

Documentation/admin-guide/pm/amd-pstate.rst +21 -0
+The platform uses the CPPC interfaces to communicate the core ranking
+to the operating system and scheduler to make sure that OS is choosing
+the cores with highest performance firstly for scheduling the process.
+When ``amd-pstate`` driver receives a message with the highest
+performance change, it will update the core ranking and set the cpu's priority.
+
+``amd-pstate`` Preferred Core Switch
+=================================
+Kernel Parameters
+-----------------
+
+``amd-pstate`` peferred core`` has two states: enable and disable.
+Enable/disable states can be chosen by different kernel parameters.
+Default enable ``amd-pstate`` preferred core.
+
+``amd_prefcore=disable``
+
+For systems that support ``amd-pstate`` preferred core, the core
+rankings will always be advertised by the platform. But OS can choose
+to ignore that via the kernel parameter ``amd_prefcore=disable``.
+
 User Space Interface in ``sysfs`` - General

===========================================

Documentation/admin-guide/pm/amd-pstate.rst +0 -0
@@ -385,6 +427,19 @@ control its functionality at the system level.  They are

located in the
to the operation mode represented by that string - or to be unregistered in the "disable" case.

+``prefcore``

Documentation/admin-guide/pm/amd-pstate.rst +12 -0
+     Preferred core state of the driver: "enabled" or "disabled".
+
+     "enabled"
+             Enable the ``amd-pstate`` preferred core.
+
+     "disabled"
+             Disable the ``amd-pstate`` preferred core
+
+
+        This attribute is read-only to check the state of preferred core set
+        by the kernel parameter.
+
 ``cpupower`` tool support for ``amd-pstate``

===============================================

Quoted 2 lines

--
2.34.1

Reviewed-by Perry Yuan < [email protected]>
author
#13 lore raw

PATCH v11 7/7 Documentation: introduce amd-pstate preferrd core mode kernel command line options

In reply to Meng Li

amd-pstate driver support enable/disable preferred core. Default enabled on platforms supporting amd-pstate preferred core. Disable amd-pstate preferred core with "amd_prefcore=disable" added to the kernel command line.

Signed-off-by Meng Li <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Tested-by Oleksandr Natalenko <[email protected]>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 1 file changed, 5 insertions(+)
Documentation/admin-guide/kernel-parameters.txt +5 -0
index 758bb25ea3e6..008bdfd63c22 100644
@@ -363,6 +363,11 @@
 			  selects a performance level in this range and appropriate
 			  to the current workload.
 
+	amd_prefcore=
+			[X86]
+			disable
+			  Disable amd-pstate preferred core.
+
 	amijoy.map=	[HW,JOY] Amiga joystick support
 			Map of devices attached to JOY0DAT and JOY1DAT
 			Format: <a>,<b>
Signature · 1 line
2.34.1
reviewer Reviewed-by on v11 7/7
#14 lore raw

RE: [PATCH V11 7/7] Documentation: introduce amd-pstate preferrd core mode kernel command line options

[AMD Official Use Only - General]

Quoted 52 lines

-----Original Message-----
From: Meng, Li (Jassmine) <[email protected]>
Sent: Wednesday, November 29, 2023 2:55 PM
To: Rafael J . Wysocki <[email protected]>; Huang, Ray <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Shuah Khan <[email protected]>; linux- [email protected]; Fontenot, Nathan <[email protected]>; Sharma, Deepak <[email protected]>; Deucher, Alexander <[email protected]>; Limonciello, Mario <[email protected]>; Huang, Shimmer <[email protected]>; Yuan, Perry <[email protected]>; Du, Xiaojian <[email protected]>; Viresh Kumar <[email protected]>; Borislav Petkov <[email protected]>; Oleksandr Natalenko <[email protected]>; Meng, Li (Jassmine) <[email protected]>; Karny, Wyes <[email protected]>
Subject: [PATCH V11 7/7] Documentation: introduce amd-pstate preferrd core mode kernel command line options

amd-pstate driver support enable/disable preferred core. Default enabled on platforms supporting amd-pstate preferred core. Disable amd-pstate preferred core with "amd_prefcore=disable" added to the kernel command line.

Signed-off-by Meng Li <[email protected]>
Reviewed-by Mario Limonciello <[email protected]>
Reviewed-by Wyes Karny <[email protected]>
Reviewed-by Huang Rui <[email protected]>
Tested-by Oleksandr Natalenko <[email protected]>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 1 file changed, 5 insertions(+)
Documentation/admin-guide/kernel-parameters.txt +0 -0
index 758bb25ea3e6..008bdfd63c22 100644
@@ -363,6 +363,11 @@
                        selects a performance level in this range and

appropriate
to the current workload.

Documentation/admin-guide/kernel-parameters.txt +5 -1
+     amd_prefcore=
+                     [X86]
+                     disable
+                       Disable amd-pstate preferred core.
+
      amijoy.map=     [HW,JOY] Amiga joystick support
                      Map of devices attached to JOY0DAT and JOY1DAT
                      Format: <a>,<b>
--
Quoted 1 line

2.34.1

Reviewed-by Perry Yuan < [email protected]>
#15 lore raw
In reply to Meng Li
Quoted 32 lines · Meng Li

Hi all:

The core frequency is subjected to the process variation in semiconductors. Not all cores are able to reach the maximum frequency respecting the infrastructure limits. Consequently, AMD has redefined the concept of maximum frequency of a part. This means that a fraction of cores can reach maximum frequency. To find the best process scheduling policy for a given scenario, OS needs to know the core ordering informed by the platform through highest performance capability register of the CPPC interface.

Earlier implementations of amd-pstate preferred core only support a static core ranking and targeted performance. Now it has the ability to dynamically change the preferred core based on the workload and platform conditions and accounting for thermals and aging.

Amd-pstate driver utilizes the functions and data structures provided by the ITMT architecture to enable the scheduler to favor scheduling on cores which can be get a higher frequency with lower voltage.
We call it amd-pstate preferred core.

Here sched_set_itmt_core_prio() is called to set priorities and sched_set_itmt_support() is called to enable ITMT feature. Amd-pstate driver uses the highest performance value to indicate the priority of CPU. The higher value has a higher priority.

Amd-pstate driver will provide an initial core ordering at boot time. It relies on the CPPC interface to communicate the core ranking to the operating system and scheduler to make sure that OS is choosing the cores with highest performance firstly for scheduling the process. When amd-pstate driver receives a message with the highest performance change, it will update the core ranking.

Quoted 4 lines

Changes from V10->V11:
- cpufreq: amd-pstate:
- - according Perry's commnts, I replace the string with str_enabled_disable().

Hi,

Using clang-17, I get the following warning:

----
drivers/cpufreq/amd-pstate.c:793:34: warning: variable 'cpudata' is
uninitialized when used here [-Wuninitialized]

    793 |         if ((!amd_pstate_prefcore) || (!cpudata->hw_prefcore))
        |                                         ^~~~~~~
  drivers/cpufreq/amd-pstate.c:789:29: note: initialize the variable 
'cpudata' to silence this warning
    789 |         struct amd_cpudata *cpudata;
        |                                    ^
        |                                     = NULL

1 warning generated.
----

Cheers,
Tor