[RFC PATCH] thermal/drivers/intel_powerclamp: Support cpumask and step_size

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

In some use cases, it is desirable to only inject idle on certain set
of CPUs. For example on Alder Lake systems, it is possible that we force
idle only on P-Cores for thermal reasons. Also the idle percent can be
more than 50% if we only choose partial set of CPUs in the system.

Introduce module parameters for setting cpumask and step_size. They
can be only changed when the cooling device is inactive. This module
already have other module parameters. There is no change done for
those parameters.

cpumask (Read/Write): A bit mask of CPUs to inject idle. The format of
this bitmask is same as used in other subsystems like in
/proc/irq/*/smp_affinity. The mask is comma separated 32 bit groups.
Each CPU is one bit. For example for 256 CPU system the full mask is:
ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff
The leftmost mask is for CPU 0-32.

step_size (Read/Write): Step size specifies a multiplication factor to
the cooling device state. The step size can be either 1 or 2. By default,
step_size = 1. When the step size = 1, the max idle percent is 50%.
When step size = 2, the max idle percent is 100%. For the step size of 2,
the cpumask should be smaller than the full system cpumask. In this way
the system wide idle injection is restricted to 50%.

Since the max state for thermal cooling can't be changed with some
thermal core changes, step_size is a way to allow more than 50% idle
percent.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 .../driver-api/thermal/intel_powerclamp.rst   |  22 +++
 drivers/thermal/intel/intel_powerclamp.c      | 166 ++++++++++++++++--
 2 files changed, 170 insertions(+), 18 deletions(-)

diff --git a/Documentation/driver-api/thermal/intel_powerclamp.rst b/Documentation/driver-api/thermal/intel_powerclamp.rst
index 3f6dfb0b3ea6..582e3e42750b 100644
--- a/Documentation/driver-api/thermal/intel_powerclamp.rst
+++ b/Documentation/driver-api/thermal/intel_powerclamp.rst
@@ -26,6 +26,8 @@ By:
 	    - Generic Thermal Layer (sysfs)
 	    - Kernel APIs (TBD)
 
+	(*) Module Parameters
+
 INTRODUCTION
 ============
 
@@ -318,3 +320,23 @@ device, a PID based userspace thermal controller can manage to
 control CPU temperature effectively, when no other thermal influence
 is added. For example, a UltraBook user can compile the kernel under
 certain temperature (below most active trip points).
+
+Module Parameters
+=================
+
+``cpumask`` (RW)
+	A bit mask of CPUs to inject idle. The format of the bitmask is same as
+	used in other subsystems like in /proc/irq/*/smp_affinity. The mask is
+	comma separated 32 bit groups. Each CPU is one bit. For example for a 256
+	CPU system the full mask is:
+	ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff
+
+	The leftmost mask is for CPU 0-32.
+
+``step_size`` (RW)
+	Step size specifies a multiplication factor to the cooling device state.
+	The step size can be either 1 or 2. By default,
+	step_size = 1. When the step size = 1, the max idle percent is 50%.
+	When step size = 2, the max idle percent is 100%. For the step size of 2,
+	the cpumask should be smaller than the full system cpumask. In this way
+	the system wide idle injection is restricted to 50%.
diff --git a/drivers/thermal/intel/intel_powerclamp.c b/drivers/thermal/intel/intel_powerclamp.c
index 320525c3c530..221c6de3e06f 100644
--- a/drivers/thermal/intel/intel_powerclamp.c
+++ b/drivers/thermal/intel/intel_powerclamp.c
@@ -108,6 +108,119 @@ static const struct kernel_param_ops duration_ops = {
 module_param_cb(duration, &duration_ops, &duration, 0644);
 MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec.");
 
+static u8 step_size = 1;
+static cpumask_var_t idle_injection_cpu_mask;
+
+static int cpumask_set(const char *arg, const struct kernel_param *kp)
+{
+	int ret;
+
+	mutex_lock(&powerclamp_lock);
+
+	/* Can't set mask when cooling device is in use */
+	if (powerclamp_data.clamping) {
+		ret = -EAGAIN;
+		goto skip_cpumask_set;
+	}
+
+	if (!idle_injection_cpu_mask) {
+		if (!zalloc_cpumask_var(&idle_injection_cpu_mask, GFP_KERNEL)) {
+			ret = -ENOMEM;
+			goto skip_cpumask_set;
+		}
+	}
+
+	ret = bitmap_parse(arg, strlen(arg), cpumask_bits(idle_injection_cpu_mask),
+			   nr_cpumask_bits);
+	if (ret)
+		goto free_cpu_mask;
+
+	if (cpumask_empty(idle_injection_cpu_mask)) {
+		ret = -EINVAL;
+		goto free_cpu_mask;
+	}
+
+	if (cpumask_equal(cpu_present_mask, idle_injection_cpu_mask) &&
+			  step_size > 1) {
+		ret = -EINVAL;
+		goto free_cpu_mask;
+	}
+
+	mutex_unlock(&powerclamp_lock);
+
+	return 0;
+
+free_cpu_mask:
+	free_cpumask_var(idle_injection_cpu_mask);
+	idle_injection_cpu_mask = NULL;
+
+skip_cpumask_set:
+	mutex_unlock(&powerclamp_lock);
+
+	return ret;
+}
+
+static int cpumask_get(char *buf, const struct kernel_param *kp)
+{
+	if (!idle_injection_cpu_mask)
+		return -EINVAL;
+
+	return bitmap_print_to_pagebuf(false, buf, cpumask_bits(idle_injection_cpu_mask),
+				       nr_cpumask_bits);
+}
+
+static const struct kernel_param_ops cpumask_ops = {
+	.set = cpumask_set,
+	.get = cpumask_get,
+};
+
+module_param_cb(cpumask, &cpumask_ops, NULL, 0644);
+MODULE_PARM_DESC(cpumask, "Mask of CPUs to use for idle injection.");
+
+static int step_size_set(const char *arg, const struct kernel_param *kp)
+{
+	u8 _step_size;
+	int ret = 0;
+
+	mutex_lock(&powerclamp_lock);
+
+	/* Can't set mask when cooling device is in use */
+	if (powerclamp_data.clamping) {
+		ret = -EAGAIN;
+		goto skip_limit_set;
+	}
+
+	ret = kstrtou8(arg, 10, &_step_size);
+	if (ret)
+		goto skip_limit_set;
+
+	if (_step_size > 2) {
+		ret = -EINVAL;
+		goto skip_limit_set;
+	}
+
+	if (idle_injection_cpu_mask && cpumask_equal(cpu_present_mask, idle_injection_cpu_mask) &&
+	    _step_size > 1) {
+		ret = -EINVAL;
+		goto skip_limit_set;
+	}
+
+	step_size = _step_size;
+
+skip_limit_set:
+	mutex_unlock(&powerclamp_lock);
+
+	return ret;
+}
+
+static const struct kernel_param_ops step_size_ops = {
+	.set = step_size_set,
+	.get = param_get_int,
+};
+
+module_param_cb(step_size, &step_size_ops, &step_size, 0644);
+MODULE_PARM_DESC(step_size, "Step size to increment for each cooling state. range 1-2");
+
 struct powerclamp_calibration_data {
 	unsigned long confidence;  /* used for calibration, basically a counter
 				    * gets incremented each time a clamping
@@ -246,6 +359,9 @@ static unsigned int get_compensation(int ratio)
 {
 	unsigned int comp = 0;
 
+	if (step_size > 1)
+		return 0;
+
 	/* we only use compensation if all adjacent ones are good */
 	if (ratio == 1 &&
 		cal_data[ratio].confidence >= CONFIDENCE_OK &&
@@ -338,6 +454,10 @@ static unsigned int get_run_time(void)
 	unsigned int compensated_ratio;
 	unsigned int runtime;
 
+	/* No compensation for non systemwide idle injection */
+	if (step_size > 1)
+		return (duration * 100 / powerclamp_data.target_ratio - duration);
+
 	/*
 	 * make sure user selected ratio does not take effect until
 	 * the next round. adjust target_ratio if user has changed
@@ -454,21 +574,26 @@ static void trigger_idle_injection(void)
  */
 static int powerclamp_idle_injection_register(void)
 {
-	/*
-	 * The idle inject core will only inject for online CPUs,
-	 * So we can register for all present CPUs. In this way
-	 * if some CPU goes online/offline while idle inject
-	 * is registered, nothing additional calls are required.
-	 * The same runtime and idle time is applicable for
-	 * newly onlined CPUs if any.
-	 *
-	 * Here cpu_present_mask can be used as is.
-	 * cast to (struct cpumask *) is required as the
-	 * cpu_present_mask is const struct cpumask *, otherwise
-	 * there will be compiler warnings.
-	 */
-	ii_dev = idle_inject_register_full((struct cpumask *)cpu_present_mask,
-					   idle_inject_update);
+	if (!idle_injection_cpu_mask) {
+		if (!zalloc_cpumask_var(&idle_injection_cpu_mask, GFP_KERNEL))
+			return -ENOMEM;
+
+		/*
+		 * The idle inject core will only inject for online CPUs,
+		 * So we can register for all present CPUs. In this way
+		 * if some CPU goes online/offline while idle inject
+		 * is registered, nothing additional calls are required.
+		 * The same runtime and idle time is applicable for
+		 * newly onlined CPUs if any.
+		 */
+		cpumask_copy(idle_injection_cpu_mask, cpu_present_mask);
+	}
+
+	if (cpumask_equal(cpu_present_mask, idle_injection_cpu_mask))
+		ii_dev = idle_inject_register_full(idle_injection_cpu_mask, idle_inject_update);
+	else
+		ii_dev = idle_inject_register(idle_injection_cpu_mask);
+
 	if (!ii_dev) {
 		pr_err("powerclamp: idle_inject_register failed\n");
 		return -EAGAIN;
@@ -504,7 +629,9 @@ static int start_power_clamp(void)
 	ret = powerclamp_idle_injection_register();
 	if (!ret) {
 		trigger_idle_injection();
-		schedule_delayed_work(&poll_pkg_cstate_work, 0);
+		/* No use of package residency counters when partial set is used */
+		if (cpumask_equal(cpu_present_mask, idle_injection_cpu_mask))
+			schedule_delayed_work(&poll_pkg_cstate_work, 0);
 	}
 
 	return ret;
@@ -558,7 +685,7 @@ static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev,
 				(unsigned long) (MAX_TARGET_RATIO - 1));
 	if (!powerclamp_data.target_ratio && new_target_ratio > 0) {
 		pr_info("Start idle injection to reduce power\n");
-		powerclamp_data.target_ratio = new_target_ratio;
+		powerclamp_data.target_ratio = new_target_ratio * step_size;
 		ret = start_power_clamp();
 		if (ret)
 			powerclamp_data.target_ratio = 0;
@@ -570,7 +697,7 @@ static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev,
 	} else	/* adjust currently running */ {
 		unsigned int runtime;
 
-		powerclamp_data.target_ratio = new_target_ratio;
+		powerclamp_data.target_ratio = new_target_ratio * step_size;
 		runtime = get_run_time();
 		idle_inject_set_duration(ii_dev, runtime, duration);
 	}
@@ -676,6 +803,9 @@ static void __exit powerclamp_exit(void)
 
 	cancel_delayed_work_sync(&poll_pkg_cstate_work);
 	debugfs_remove_recursive(debug_dir);
+
+	if (idle_injection_cpu_mask)
+		free_cpumask_var(idle_injection_cpu_mask);
 }
 module_exit(powerclamp_exit);
 
-- 
2.37.2