Re: [PATCH V1 2/6] cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting.

From: Mario Limonciello
Date: Tue Aug 08 2023 - 11:52:47 EST

On 8/8/2023 03:09, Meng Li wrote:
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.

By using this function you need to also ensure that CONFIG_SCHED_MC_PRIO has been set up in drivers/cpufreq/Kconfig.x86 when amd-pstate is used.

Also I think it's worth changing arch/x86/Kconfig to:
1) Drop the requirement for CPU_SUP_INTEL
2) select X86_AMD_PSTATE

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 device attribute for preferred core states.

Add one new early parameter `enable` to allow user to
enable the preferred core if the processor and power
firmware can support preferred core feature.

Signed-off-by: Meng Li <li.meng@xxxxxxx>
Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
---
drivers/cpufreq/amd-pstate.c | 149 +++++++++++++++++++++++++++++++----
1 file changed, 133 insertions(+), 16 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 9a1e194d5cf8..e919b3f4ab18 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -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 +50,8 @@
#define AMD_PSTATE_TRANSITION_LATENCY 20000
#define AMD_PSTATE_TRANSITION_DELAY 1000
+#define AMD_PSTATE_PREFCORE_THRESHOLD 166
+#define AMD_PSTATE_MAX_CPPC_PERF 255
/*
* TODO: We need more time to fine tune processors with shared memory solution
@@ -65,6 +68,14 @@ static struct cpufreq_driver amd_pstate_epp_driver;
static int cppc_state = AMD_PSTATE_UNDEFINED;
static bool cppc_enabled;
+/*
+ * CPPC Preferred Core feature is supported by power firmware
+ */
+static bool prefcore_enabled = false;
+
+/* Disable AMD Pstate Preferred Core loading */
+static bool no_prefcore __read_mostly = true;
+
/*
* AMD Energy Preference Performance (EPP)
* The EPP is used in the CCLK DPM controller to drive
@@ -290,23 +301,21 @@ 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 (!prefcore_enabled)
+ WRITE_ONCE(cpudata->highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
+ else
+ WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);
WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));
@@ -318,17 +327,15 @@ 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 (!prefcore_enabled)
+ WRITE_ONCE(cpudata->highest_perf, cppc_perf.highest_perf);
+ else
+ WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);
WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
WRITE_ONCE(cpudata->lowest_nonlinear_perf,
@@ -676,6 +683,90 @@ 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, u64 *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 {
+ ret = cppc_get_highest_perf(cpu, highest_perf);
+ }
+
+ return (ret);
+}
+
+static void amd_pstate_init_prefcore(void)
+{
+ int cpu, ret;
+ u64 highest_perf;
+
+ if (no_prefcore)
+ return;
+
+ for_each_possible_cpu(cpu) {
+ ret = amd_pstate_get_highest_perf(cpu, &highest_perf);
+ if (ret)
+ break;
+
+ sched_set_itmt_core_prio(highest_perf, cpu);
+ }
+
+ /*
+ * This code can be run during CPU online under the
+ * CPU hotplug locks, so sched_set_amd_prefcore_support()
+ * cannot be called from here. Queue up a work item
+ * to invoke it.
+ */
+ schedule_work(&sched_prefcore_work);
+}
+
+/*
+ * Check if AMD Pstate Preferred core feature is supported and enabled
+ * 1) no_prefcore is used to enable or disable AMD Pstate Preferred Core
+ * loading when user would like to enable or disable it. Without that,
+ * AMD Pstate Preferred Core will be disabled by default if the processor
+ * and power firmware can support preferred core feature.
+ * 2) prefcore_enabled is used to indicate whether CPPC preferred core is enabled.
+ */
+static void check_prefcore_supported(int cpu)
+{
+ u64 highest_perf;
+ int ret;
+
+ if (no_prefcore)
+ return;
+
+ ret = amd_pstate_get_highest_perf(cpu, &highest_perf);
+ if (ret)
+ return;
+
+ if(highest_perf < AMD_PSTATE_MAX_CPPC_PERF)
+ prefcore_enabled = true;
+}
+
static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
{
int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
@@ -697,6 +788,9 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
cpudata->cpu = policy->cpu;
+ /* check if CPPC preferred core feature is enabled*/
+ check_prefcore_supported(policy->cpu);
+
ret = amd_pstate_init_perf(cpudata);
if (ret)
goto free_cpudata1;
@@ -1037,6 +1131,12 @@ static ssize_t status_store(struct device *a, struct device_attribute *b,
return ret < 0 ? ret : count;
}
+static ssize_t prefcore_state_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%s\n", prefcore_enabled ? "enabled" : "disabled");
+}
+
cpufreq_freq_attr_ro(amd_pstate_max_freq);
cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
@@ -1044,6 +1144,7 @@ cpufreq_freq_attr_ro(amd_pstate_highest_perf);
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_state);
static struct freq_attr *amd_pstate_attr[] = {
&amd_pstate_max_freq,
@@ -1063,6 +1164,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
static struct attribute *pstate_global_attributes[] = {
&dev_attr_status.attr,
+ &dev_attr_prefcore_state.attr,
NULL
};
@@ -1114,6 +1216,9 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
cpudata->cpu = policy->cpu;
cpudata->epp_policy = 0;
+ /* check if CPPC preferred core feature is supported*/
+ check_prefcore_supported(policy->cpu);
+
ret = amd_pstate_init_perf(cpudata);
if (ret)
goto free_cpudata1;
@@ -1506,6 +1611,8 @@ static int __init amd_pstate_init(void)
}
}
+ amd_pstate_init_prefcore();
+
return ret;
global_attr_free:
@@ -1527,7 +1634,17 @@ 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, "enable"))
+ no_prefcore = false;
+
+ return 0;
+}
+
early_param("amd_pstate", amd_pstate_param);
+early_param("amd_prefcore", amd_prefcore_param);
MODULE_AUTHOR("Huang Rui <ray.huang@xxxxxxx>");
MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");