[PATCH v2 3/5] cpufreq: intel_pstate: Add ->offline and ->online callbacks

Rafael J. Wysocki
2020-08-24T17:48:43Z

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Add ->offline and ->online driver callbacks to prepare for taking a
CPU offline and to restore its working configuration when it goes
back online, respectively, to avoid invoking the ->init callback on
every CPU online which is quite a bit of unnecessary overhead.

Define ->offline and ->online so that they can be used in the
passive mode as well as in the active mode and because ->offline
will do the majority of ->stop_cpu work, the passive mode does
not need that callback any more, so drop it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

-> v2: Typo fixes and changelog edits (Doug).

---
drivers/cpufreq/intel_pstate.c | 38 ++++++++++++++++++++++++++++------
1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 3d18934fa975..98836ac299db 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2297,28 +2297,51 @@ static int intel_pstate_verify_policy(struct cpufreq_policy_data *policy)
return 0;
}

-static void intel_cpufreq_stop_cpu(struct cpufreq_policy *policy)
+static int intel_pstate_cpu_offline(struct cpufreq_policy *policy)
{
+ pr_debug("CPU %d going offline\n", policy->cpu);
+
+ intel_pstate_exit_perf_limits(policy);
+
+ /*
+ * If the CPU is an SMT thread and it goes offline with the performance
+ * settings different from the minimum, it will prevent its sibling
+ * from getting to lower performance levels, so force the minimum
+ * performance on CPU offline to prevent that from happening.
+ */
if (hwp_active)
intel_pstate_hwp_force_min_perf(policy->cpu);
else
intel_pstate_set_min_pstate(all_cpu_data[policy->cpu]);
+
+ return 0;
+}
+
+static int intel_pstate_cpu_online(struct cpufreq_policy *policy)
+{
+ pr_debug("CPU %d going online\n", policy->cpu);
+
+ intel_pstate_init_acpi_perf_limits(policy);
+
+ if (hwp_active)
+ wrmsrl_on_cpu(policy->cpu, MSR_HWP_REQUEST,
+ all_cpu_data[policy->cpu]->hwp_req_cached);
+
+ return 0;
}

static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
{
- pr_debug("CPU %d exiting\n", policy->cpu);
+ pr_debug("CPU %d stopping\n", policy->cpu);

intel_pstate_clear_update_util_hook(policy->cpu);
if (hwp_active)
intel_pstate_hwp_save_state(policy);
-
- intel_cpufreq_stop_cpu(policy);
}

static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
{
- intel_pstate_exit_perf_limits(policy);
+ pr_debug("CPU %d exiting\n", policy->cpu);

policy->fast_switch_possible = false;

@@ -2398,6 +2421,8 @@ static struct cpufreq_driver intel_pstate = {
.init = intel_pstate_cpu_init,
.exit = intel_pstate_cpu_exit,
.stop_cpu = intel_pstate_stop_cpu,
+ .offline = intel_pstate_cpu_offline,
+ .online = intel_pstate_cpu_online,
.update_limits = intel_pstate_update_limits,
.name = "intel_pstate",
};
@@ -2652,7 +2677,8 @@ static struct cpufreq_driver intel_cpufreq = {
.fast_switch = intel_cpufreq_fast_switch,
.init = intel_cpufreq_cpu_init,
.exit = intel_cpufreq_cpu_exit,
- .stop_cpu = intel_cpufreq_stop_cpu,
+ .offline = intel_pstate_cpu_offline,
+ .online = intel_pstate_cpu_online,
.update_limits = intel_pstate_update_limits,
.name = "intel_cpufreq",
};
--
2.26.2