[PATCH v6 3/6] cpufreq: amd_pstate: Add guided autonomous mode

Wyes Karny
2023-02-06T17:24:29Z

From ACPI spec below 3 modes for CPPC can be defined:
1. Non autonomous: OS scaling governor specifies operating frequency/
performance level through `Desired Performance` register and platform
follows that.
2. Guided autonomous: OS scaling governor specifies min and max
frequencies/ performance levels through `Minimum Performance` and
`Maximum Performance` register, and platform can autonomously select an
operating frequency in this range.
3. Fully autonomous: OS only hints (via EPP) to platform for the required
energy performance preference for the workload and platform autonomously
scales the frequency.

Currently (1) is supported by amd_pstate as passive mode, and (3) is
implemented by EPP support. This change is to support (2).

In guided autonomous mode the min_perf is based on the input from the
scaling governor. For example, in case of schedutil this value depends
on the current utilization. And max_perf is set to max capacity.

To activate guided auto mode ``amd_pstate=guided`` command line
parameter has to be passed in the kernel.

Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
---
.../admin-guide/kernel-parameters.txt | 15 +++++---
drivers/cpufreq/amd-pstate.c | 34 +++++++++++++++----
include/linux/amd-pstate.h | 2 ++
3 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e3618dfdb36a..56d5c189e458 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -7015,11 +7015,11 @@
Do not enable amd_pstate as the default
scaling driver for the supported processors
passive
- Use amd_pstate as a scaling driver, driver requests a
- desired performance on this abstract scale and the power
- management firmware translates the requests into actual
- hardware states (core frequency, data fabric and memory
- clocks etc.)
+ Use amd_pstate with passive mode as a scaling driver.
+ In this mode autonomous selection is disabled.
+ Driver requests a desired performance level and platform
+ tries to match the same performance level if it is
+ satisfied by guaranteed performance level.
active
Use amd_pstate_epp driver instance as the scaling driver,
driver provides a hint to the hardware if software wants
@@ -7027,3 +7027,8 @@
to the CPPC firmware. then CPPC power algorithm will
calculate the runtime workload and adjust the realtime cores
frequency.
+ guided
+ Activate guided autonomous 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.
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 168a28bed6ee..6582c922ad3a 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -308,7 +308,22 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
cppc_perf.lowest_nonlinear_perf);
WRITE_ONCE(cpudata->lowest_perf, cppc_perf.lowest_perf);

- return 0;
+ if (cppc_state == AMD_PSTATE_ACTIVE)
+ return 0;
+
+ ret = cppc_get_auto_sel_caps(cpudata->cpu, &cppc_perf);
+ if (ret) {
+ pr_warn("failed to get auto_sel, ret: %d\n", ret);
+ return 0;
+ }
+
+ ret = cppc_set_auto_sel(cpudata->cpu,
+ (cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
+
+ if (ret)
+ pr_warn("failed to set auto_sel, ret: %d\n", ret);
+
+ return ret;
}

DEFINE_STATIC_CALL(amd_pstate_init_perf, pstate_init_perf);
@@ -385,12 +400,18 @@ static inline bool amd_pstate_sample(struct amd_cpudata *cpudata)
}

static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
- u32 des_perf, u32 max_perf, bool fast_switch)
+ u32 des_perf, u32 max_perf, bool fast_switch, int gov_flags)
{
u64 prev = READ_ONCE(cpudata->cppc_req_cached);
u64 value = prev;

des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
+
+ if ((cppc_state == AMD_PSTATE_GUIDED) && (gov_flags & CPUFREQ_GOV_DYNAMIC_SWITCHING)) {
+ min_perf = des_perf;
+ des_perf = 0;
+ }
+
value &= ~AMD_CPPC_MIN_PERF(~0L);
value |= AMD_CPPC_MIN_PERF(min_perf);

@@ -445,7 +466,7 @@ static int amd_pstate_target(struct cpufreq_policy *policy,

cpufreq_freq_transition_begin(policy, &freqs);
amd_pstate_update(cpudata, min_perf, des_perf,
- max_perf, false);
+ max_perf, false, policy->governor->flags);
cpufreq_freq_transition_end(policy, &freqs, false);

return 0;
@@ -479,7 +500,8 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
if (max_perf < min_perf)
max_perf = min_perf;

- amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true);
+ amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true,
+ policy->governor->flags);
cpufreq_cpu_put(policy);
}

@@ -1279,7 +1301,7 @@ static int __init amd_pstate_init(void)
/* capability check */
if (boot_cpu_has(X86_FEATURE_CPPC)) {
pr_debug("AMD CPPC MSR based functionality is supported\n");
- if (cppc_state == AMD_PSTATE_PASSIVE)
+ if (cppc_state != AMD_PSTATE_ACTIVE)
current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
} else {
pr_debug("AMD CPPC shared memory based functionality is supported\n");
@@ -1341,7 +1363,7 @@ static int __init amd_pstate_param(char *str)
if (cppc_state == AMD_PSTATE_ACTIVE)
current_pstate_driver = &amd_pstate_epp_driver;

- if (cppc_state == AMD_PSTATE_PASSIVE)
+ if (cppc_state == AMD_PSTATE_PASSIVE || cppc_state == AMD_PSTATE_GUIDED)
current_pstate_driver = &amd_pstate_driver;

return 0;
diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
index f5f22418e64b..c10ebf8c42e6 100644
--- a/include/linux/amd-pstate.h
+++ b/include/linux/amd-pstate.h
@@ -97,6 +97,7 @@ enum amd_pstate_mode {
AMD_PSTATE_DISABLE = 0,
AMD_PSTATE_PASSIVE,
AMD_PSTATE_ACTIVE,
+ AMD_PSTATE_GUIDED,
AMD_PSTATE_MAX,
};

@@ -104,6 +105,7 @@ static const char * const amd_pstate_mode_string[] = {
[AMD_PSTATE_DISABLE] = "disable",
[AMD_PSTATE_PASSIVE] = "passive",
[AMD_PSTATE_ACTIVE] = "active",
+ [AMD_PSTATE_GUIDED] = "guided",
NULL,
};
#endif /* _LINUX_AMD_PSTATE_H */
--
2.34.1