[PATCH 2/2] intel_pstate: Add support for HWP

From: dirk . brandewie
Date: Thu Nov 06 2014 - 12:41:10 EST

From: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>

Add support of Hardware Managed Performance States (HWP) described in Volume 3
section 14.4 of the SDM.

With HWP enbaled intel_pstate will no longer be responsible for selecting P
states for the processor. intel_pstate will continue to register to
the cpufreq core as the scaling driver for CPUs implementing
HWP. In HWP mode intel_pstate provides three functions reporting
frequency to the cpufreq core, support for the set_policy() interface
from the core and maintaining the intel_pstate sysfs interface in
/sys/devices/system/cpu/intel_pstate. User preferences expressed via
the set_policy() interface or the sysfs interface are forwared to the
CPU via the HWP MSR interface.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
---
Documentation/cpu-freq/intel-pstate.txt | 37 ++++++++----
Documentation/kernel-parameters.txt | 3 +
arch/x86/include/uapi/asm/msr-index.h | 41 +++++++++++++
drivers/cpufreq/intel_pstate.c | 102 +++++++++++++++++++++++++++++++-
4 files changed, 168 insertions(+), 15 deletions(-)

diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
index a69ffe1..765d7fc 100644
--- a/Documentation/cpu-freq/intel-pstate.txt
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -1,17 +1,28 @@
Intel P-state driver
--------------------

-This driver implements a scaling driver with an internal governor for
-Intel Core processors. The driver follows the same model as the
-Transmeta scaling driver (longrun.c) and implements the setpolicy()
-instead of target(). Scaling drivers that implement setpolicy() are
-assumed to implement internal governors by the cpufreq core. All the
-logic for selecting the current P state is contained within the
-driver; no external governor is used by the cpufreq core.
-
-Intel SandyBridge+ processors are supported.
-
-New sysfs files for controlling P state selection have been added to
+This driver provides an interface to control the P state selection for
+SandyBridge+ Intel processors. The driver can operate two different
+modes based on the processor model legacy and Hardware P state (HWP)
+mode.
+
+In legacy mode the driver implements a scaling driver with an internal
+governor for Intel Core processors. The driver follows the same model
+as the Transmeta scaling driver (longrun.c) and implements the
+setpolicy() instead of target(). Scaling drivers that implement
+setpolicy() are assumed to implement internal governors by the cpufreq
+core. All the logic for selecting the current P state is contained
+within the driver; no external governor is used by the cpufreq core.
+
+In HWP mode P state selection is implemented in the processor
+itself. The driver provides the interfaces between the cpufreq core and
+the processor to control P state selection based on user preferences
+and reporting frequency to the cpufreq core. In this mode the
+internal governor code is disabled.
+
+In addtion to the interfaces provided by the cpufreq core for
+controlling frequency the driver provides sysfs files for
+controlling P state selection. These files have been added to
/sys/devices/system/cpu/intel_pstate/

max_perf_pct: limits the maximum P state that will be requested by
@@ -33,7 +44,9 @@ frequency is fiction for Intel Core processors. Even if the scaling
driver selects a single P state the actual frequency the processor
will run at is selected by the processor itself.

-New debugfs files have also been added to /sys/kernel/debug/pstate_snb/
+For legacy mode debugfs files have also been added to allow tuning of
+the internal governor algorythm. These files are located at
+/sys/kernel/debug/pstate_snb/ These files are NOT present in HWP mode.

deadband
d_gain_pct
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4c81a86..571f9d2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1446,6 +1446,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
disable
Do not enable intel_pstate as the default
scaling driver for the supported processors
+ no_hwp
+ Do not enable hardware P state control (HWP)
+ if available.

intremap= [X86-64, Intel-IOMMU]
on enable Interrupt Remapping (default)
diff --git a/arch/x86/include/uapi/asm/msr-index.h b/arch/x86/include/uapi/asm/msr-index.h
index e21331c..86dda97 100644
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -152,6 +152,45 @@
#define MSR_CC6_DEMOTION_POLICY_CONFIG 0x00000668
#define MSR_MC6_DEMOTION_POLICY_CONFIG 0x00000669

+/* Hardware P state interface */
+#define MSR_PPERF 0x0000064e
+#define MSR_PERF_LIMIT_REASONS 0x0000064f
+#define MSR_PM_ENABLE 0x00000770
+#define MSR_HWP_CAPABILITIES 0x00000771
+#define MSR_HWP_REQUEST_PKG 0x00000772
+#define MSR_HWP_INTERRUPT 0x00000773
+#define MSR_HWP_REQUEST 0x00000774
+#define MSR_HWP_STATUS 0x00000777
+
+/* CPUID.6.EAX */
+#define HWP_BASE_BIT (1<<7)
+#define HWP_NOTIFICATIONS_BIT (1<<8)
+#define HWP_ACTIVITY_WINDOW_BIT (1<<9)
+#define HWP_ENERGY_PERF_PREFERENCE_BIT (1<<10)
+#define HWP_PACKAGE_LEVEL_REQUEST_BIT (1<<11)
+
+/* IA32_HWP_CAPABILITIES */
+#define HWP_HIGHEST_PERF(x) (x & 0xff)
+#define HWP_GUARANTEED_PERF(x) ((x & (0xff << 8)) >>8)
+#define HWP_MOSTEFFICIENT_PERF(x) ((x & (0xff << 16)) >>16)
+#define HWP_LOWEST_PERF(x) ((x & (0xff << 24)) >>24)
+
+/* IA32_HWP_REQUEST */
+#define HWP_MIN_PERF(x) (x & 0xff)
+#define HWP_MAX_PERF(x) ((x & 0xff) << 8)
+#define HWP_DESIRED_PERF(x) ((x & 0xff) << 16)
+#define HWP_ENERGY_PERF_PREFERENCE(x) ((x & 0xff) << 24)
+#define HWP_ACTIVITY_WINDOW(x) ((x & 0xff3) << 32)
+#define HWP_PACKAGE_CONTROL(x) ((x & 0x1) << 42)
+
+/* IA32_HWP_STATUS */
+#define HWP_GUARANTEED_CHANGE(x) (x & 0x1)
+#define HWP_EXCURSION_TO_MINIMUM(x) (x & 0x4)
+
+/* IA32_HWP_INTERRUPT */
+#define HWP_CHANGE_TO_GUARANTEED_INT(x) (x & 0x1)
+#define HWP_EXCURSION_TO_MINIMUM_INT(x) (x & 0x2)
+
#define MSR_AMD64_MC0_MASK 0xc0010044

#define MSR_IA32_MCx_CTL(x) (MSR_IA32_MC0_CTL + 4*(x))
@@ -345,6 +384,8 @@

#define MSR_IA32_TEMPERATURE_TARGET 0x000001a2

+#define MSR_MISC_PWR_MGMT 0x000001aa
+
#define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0
#define ENERGY_PERF_BIAS_PERFORMANCE 0
#define ENERGY_PERF_BIAS_NORMAL 6
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 27bb6d3..5d66dc5 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -137,6 +137,7 @@ struct cpu_defaults {

static struct pstate_adjust_policy pid_params;
static struct pstate_funcs pstate_funcs;
+static int hwp_active;

struct perf_limits {
int no_turbo;
@@ -244,6 +245,34 @@ static inline void update_turbo_state(void)
cpu->pstate.max_pstate == cpu->pstate.turbo_pstate);
}

+#define PCT_TO_HWP(x) (x * 255 / 100)
+static void intel_pstate_hwp_set(void)
+{
+ int min, max, cpu;
+ u64 value, freq, pct;
+
+ get_online_cpus();
+
+ for_each_online_cpu(cpu) {
+ rdmsrl_on_cpu(cpu, MSR_HWP_REQUEST, &value);
+ min = PCT_TO_HWP(limits.min_perf_pct);
+ value &= ~HWP_MIN_PERF(~0L);
+ value |= HWP_MIN_PERF(min);
+
+ max = PCT_TO_HWP(limits.max_perf_pct);
+ if (limits.no_turbo) {
+ rdmsrl( MSR_HWP_CAPABILITIES, freq);
+ max = HWP_GUARANTEED_PERF(freq);
+ }
+
+ value &= ~HWP_MAX_PERF(~0L);
+ value |= HWP_MAX_PERF(max);
+ wrmsrl_on_cpu(cpu, MSR_HWP_REQUEST, value);
+ }
+
+ put_online_cpus();
+}
+
/************************** debugfs begin ************************/
static int pid_param_set(void *data, u64 val)
{
@@ -279,6 +308,8 @@ static void __init intel_pstate_debug_expose_params(void)
struct dentry *debugfs_parent;
int i = 0;

+ if (hwp_active)
+ return;
debugfs_parent = debugfs_create_dir("pstate_snb", NULL);
if (IS_ERR_OR_NULL(debugfs_parent))
return;
@@ -329,8 +360,12 @@ static ssize_t store_no_turbo(struct kobject *a, struct attribute *b,
pr_warn("Turbo disabled by BIOS or unavailable on processor\n");
return -EPERM;
}
+
limits.no_turbo = clamp_t(int, input, 0, 1);

+ if (hwp_active)
+ intel_pstate_hwp_set();
+
return count;
}

@@ -348,6 +383,8 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b,
limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));

+ if (hwp_active)
+ intel_pstate_hwp_set();
return count;
}

@@ -362,7 +399,9 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
return -EINVAL;
limits.min_perf_pct = clamp_t(int, input, 0 , 100);
limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
-
+
+ if (hwp_active)
+ intel_pstate_hwp_set();
return count;
}

@@ -395,8 +434,16 @@ static void __init intel_pstate_sysfs_expose_params(void)
rc = sysfs_create_group(intel_pstate_kobject, &intel_pstate_attr_group);
BUG_ON(rc);
}
-
/************************** sysfs end ************************/
+
+static void intel_pstate_hwp_enable(void)
+{
+ hwp_active++;
+ pr_info("intel_pstate HWP enabled\n");
+
+ wrmsrl( MSR_PM_ENABLE, 0x1);
+}
+
static int byt_get_min_pstate(void)
{
u64 value;
@@ -648,6 +695,14 @@ static inline void intel_pstate_sample(struct cpudata *cpu)
cpu->prev_mperf = mperf;
}

+static inline void intel_hwp_set_sample_time(struct cpudata *cpu)
+{
+ int delay;
+
+ delay = msecs_to_jiffies(50);
+ mod_timer_pinned(&cpu->timer, jiffies + delay);
+}
+
static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
{
int delay;
@@ -694,6 +749,14 @@ static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
}

+static void intel_hwp_timer_func(unsigned long __data)
+{
+ struct cpudata *cpu = (struct cpudata *) __data;
+
+ intel_pstate_sample(cpu);
+ intel_hwp_set_sample_time(cpu);
+}
+
static void intel_pstate_timer_func(unsigned long __data)
{
struct cpudata *cpu = (struct cpudata *) __data;
@@ -737,6 +800,11 @@ static const struct x86_cpu_id intel_pstate_cpu_ids[] = {
};
MODULE_DEVICE_TABLE(x86cpu, intel_pstate_cpu_ids);

+static const struct x86_cpu_id intel_pstate_cpu_oob_ids[] = {
+ ICPU(0x56, core_params),
+ {}
+};
+
static int intel_pstate_init_cpu(unsigned int cpunum)
{
struct cpudata *cpu;
@@ -753,9 +821,14 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
intel_pstate_get_cpu_pstates(cpu);

init_timer_deferrable(&cpu->timer);
- cpu->timer.function = intel_pstate_timer_func;
cpu->timer.data = (unsigned long)cpu;
cpu->timer.expires = jiffies + HZ/100;
+
+ if (!hwp_active) {
+ cpu->timer.function = intel_pstate_timer_func;
+ } else {
+ cpu->timer.function = intel_hwp_timer_func;
+ }
intel_pstate_busy_pid_reset(cpu);
intel_pstate_sample(cpu);

@@ -792,6 +865,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
limits.no_turbo = 0;
return 0;
}
+
limits.min_perf_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
limits.min_perf_pct = clamp_t(int, limits.min_perf_pct, 0 , 100);
limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
@@ -801,6 +875,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));

+ if (hwp_active)
+ intel_pstate_hwp_set();
+
return 0;
}

@@ -823,6 +900,9 @@ static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
pr_info("intel_pstate CPU %d exiting\n", cpu_num);

del_timer_sync(&all_cpu_data[cpu_num]->timer);
+ if (hwp_active)
+ return;
+
intel_pstate_set_pstate(cpu, cpu->pstate.min_pstate);
}

@@ -866,6 +946,7 @@ static struct cpufreq_driver intel_pstate_driver = {
};

static int __initdata no_load;
+static int __initdata no_hwp;

static int intel_pstate_msrs_not_valid(void)
{
@@ -959,6 +1040,15 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
{
struct acpi_table_header hdr;
struct hw_vendor_info *v_info;
+ const struct x86_cpu_id *id;
+ u64 misc_pwr;
+
+ id = x86_match_cpu(intel_pstate_cpu_oob_ids);
+ if (id) {
+ rdmsrl(MSR_MISC_PWR_MGMT, misc_pwr);
+ if ( misc_pwr & (1 << 8))
+ return true;
+ }

if (acpi_disabled ||
ACPI_FAILURE(acpi_get_table_header(ACPI_SIG_FADT, 0, &hdr)))
@@ -982,6 +1072,7 @@ static int __init intel_pstate_init(void)
int cpu, rc = 0;
const struct x86_cpu_id *id;
struct cpu_defaults *cpu_info;
+ struct cpuinfo_x86 *c = &boot_cpu_data;

if (no_load)
return -ENODEV;
@@ -1011,6 +1102,9 @@ static int __init intel_pstate_init(void)
if (!all_cpu_data)
return -ENOMEM;

+ if (cpu_has(c,X86_FEATURE_HWP) && !no_hwp)
+ intel_pstate_hwp_enable();
+
rc = cpufreq_register_driver(&intel_pstate_driver);
if (rc)
goto out;
@@ -1041,6 +1135,8 @@ static int __init intel_pstate_setup(char *str)

if (!strcmp(str, "disable"))
no_load = 1;
+ if (!strcmp(str, "no_hwp"))
+ no_hwp = 1;
return 0;
}
early_param("intel_pstate", intel_pstate_setup);
--
1.9.3

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