[PATCH V4 2/2] cpufreq: intel_pstate: Implement QoS supported freq constraints

[Viresh Kumar]

Intel pstate driver exposes min_perf_pct and max_perf_pct sysfs files,
which can be used to force a limit on the min/max P state of the driver.
Though these files eventually control the min/max frequencies that the
CPUs will run at, they don't make a change to policy->min/max values.

When the values of these files are changed (in passive mode of the
driver), it leads to calling ->limits() callback of the cpufreq
governors, like schedutil. On a call to it the governors shall
forcefully update the frequency to come within the limits. Since the
limits, i.e.  policy->min/max, aren't updated by the driver, the
governors fails to get the target freq within limit and sometimes aborts
the update believing that the frequency is already set to the target
value.

This patch implements the QoS supported frequency constraints to update
policy->min/max values whenever min_perf_pct or max_perf_pct files are
updated. This is only done for the passive mode as of now, as the driver
is already working fine in active mode.

Fixes: ecd288429126 ("cpufreq: schedutil: Don't set next_freq to UINT_MAX")
Reported-by: Doug Smythies <dsmythies@xxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
V3->V4:
- Reimplemented the solution using QoS constraints instead of
  resolve_freq() callback.

 drivers/cpufreq/intel_pstate.c | 120 +++++++++++++++++++++++++++++++--
 1 file changed, 116 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index cc27d4c59dca..e9fbd6c36822 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -24,6 +24,7 @@
 #include <linux/fs.h>
 #include <linux/acpi.h>
 #include <linux/vmalloc.h>
+#include <linux/pm_qos.h>
 #include <trace/events/power.h>
 
 #include <asm/div64.h>
@@ -1085,6 +1086,47 @@ static ssize_t store_no_turbo(struct kobject *a, struct kobj_attribute *b,
 	return count;
 }
 
+static struct cpufreq_driver intel_pstate;
+
+static void update_qos_request(enum dev_pm_qos_req_type type)
+{
+	int max_state, turbo_max, freq, i, perf_pct;
+	struct dev_pm_qos_request *req;
+	struct cpufreq_policy *policy;
+
+	for_each_possible_cpu(i) {
+		struct cpudata *cpu = all_cpu_data[i];
+
+		policy = cpufreq_cpu_get(i);
+		if (!policy)
+			continue;
+
+		req = policy->driver_data;
+		cpufreq_cpu_put(policy);
+
+		if (!req)
+			continue;
+
+		if (hwp_active)
+			intel_pstate_get_hwp_max(i, &turbo_max, &max_state);
+		else
+			turbo_max = cpu->pstate.turbo_pstate;
+
+		if (type == DEV_PM_QOS_MIN_FREQUENCY) {
+			perf_pct = global.min_perf_pct;
+		} else {
+			req++;
+			perf_pct = global.max_perf_pct;
+		}
+
+		freq = DIV_ROUND_UP(turbo_max * perf_pct, 100);
+		freq *= cpu->pstate.scaling;
+
+		if (dev_pm_qos_update_request(req, freq))
+			pr_warn("Failed to update freq constraint: CPU%d\n", i);
+	}
+}
+
 static ssize_t store_max_perf_pct(struct kobject *a, struct kobj_attribute *b,
 				  const char *buf, size_t count)
 {
@@ -1108,7 +1150,10 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct kobj_attribute *b,
 
 	mutex_unlock(&intel_pstate_limits_lock);
 
-	intel_pstate_update_policies();
+	if (intel_pstate_driver == &intel_pstate)
+		intel_pstate_update_policies();
+	else
+		update_qos_request(DEV_PM_QOS_MAX_FREQUENCY);
 
 	mutex_unlock(&intel_pstate_driver_lock);
 
@@ -1139,7 +1184,10 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct kobj_attribute *b,
 
 	mutex_unlock(&intel_pstate_limits_lock);
 
-	intel_pstate_update_policies();
+	if (intel_pstate_driver == &intel_pstate)
+		intel_pstate_update_policies();
+	else
+		update_qos_request(DEV_PM_QOS_MIN_FREQUENCY);
 
 	mutex_unlock(&intel_pstate_driver_lock);
 
@@ -2332,8 +2380,16 @@ static unsigned int intel_cpufreq_fast_switch(struct cpufreq_policy *policy,
 
 static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
 {
-	int ret = __intel_pstate_cpu_init(policy);
+	int max_state, turbo_max, min_freq, max_freq, ret;
+	struct dev_pm_qos_request *req;
+	struct cpudata *cpu;
+	struct device *dev;
+
+	dev = get_cpu_device(policy->cpu);
+	if (!dev)
+		return -ENODEV;
 
+	ret = __intel_pstate_cpu_init(policy);
 	if (ret)
 		return ret;
 
@@ -2342,7 +2398,63 @@ static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	/* This reflects the intel_pstate_get_cpu_pstates() setting. */
 	policy->cur = policy->cpuinfo.min_freq;
 
+	req = kcalloc(2, sizeof(*req), GFP_KERNEL);
+	if (!req) {
+		ret = -ENOMEM;
+		goto pstate_exit;
+	}
+
+	cpu = all_cpu_data[policy->cpu];
+
+	if (hwp_active)
+		intel_pstate_get_hwp_max(policy->cpu, &turbo_max, &max_state);
+	else
+		turbo_max = cpu->pstate.turbo_pstate;
+
+	min_freq = DIV_ROUND_UP(turbo_max * global.min_perf_pct, 100);
+	min_freq *= cpu->pstate.scaling;
+	max_freq = DIV_ROUND_UP(turbo_max * global.max_perf_pct, 100);
+	max_freq *= cpu->pstate.scaling;
+
+	ret = dev_pm_qos_add_request(dev, req, DEV_PM_QOS_MIN_FREQUENCY,
+				     min_freq);
+	if (ret < 0) {
+		dev_err(dev, "Failed to add min-freq constraint (%d)\n", ret);
+		goto free_req;
+	}
+
+	ret = dev_pm_qos_add_request(dev, req + 1, DEV_PM_QOS_MAX_FREQUENCY,
+				     max_freq);
+	if (ret < 0) {
+		dev_err(dev, "Failed to add max-freq constraint (%d)\n", ret);
+		goto remove_min_req;
+	}
+
+	policy->driver_data = req;
+
 	return 0;
+
+remove_min_req:
+	dev_pm_qos_remove_request(req);
+free_req:
+	kfree(req);
+pstate_exit:
+	intel_pstate_exit_perf_limits(policy);
+
+	return ret;
+}
+
+static int intel_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+	struct dev_pm_qos_request *req;
+
+	req = policy->driver_data;
+
+	dev_pm_qos_remove_request(req + 1);
+	dev_pm_qos_remove_request(req);
+	kfree(req);
+
+	return intel_pstate_cpu_exit(policy);
 }
 
 static struct cpufreq_driver intel_cpufreq = {
@@ -2351,7 +2463,7 @@ static struct cpufreq_driver intel_cpufreq = {
 	.target		= intel_cpufreq_target,
 	.fast_switch	= intel_cpufreq_fast_switch,
 	.init		= intel_cpufreq_cpu_init,
-	.exit		= intel_pstate_cpu_exit,
+	.exit		= intel_cpufreq_cpu_exit,
 	.stop_cpu	= intel_cpufreq_stop_cpu,
 	.update_limits	= intel_pstate_update_limits,
 	.name		= "intel_cpufreq",
-- 
2.21.0.rc0.269.g1a574e7a288b