[PATCH 41/45] OPTIONAL: cpufreq: intel_pstate: Expose VLP controller parameters via debugfs.

[Chris Wilson]

From: Francisco Jerez <currojerez at riseup.net>

This is not required for the controller to work but has proven very
useful for debugging and testing of alternative heuristic parameters,
which may offer a better trade-off between energy efficiency and
latency.  A warning is printed out which should taint the kernel for
the non-standard calibration of the heuristic to be obvious in bug
reports.

v2: Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
    for debugfs files (Julia).  Add realtime statistic threshold and
    averaging frequency parameters.
v3: Define generic CPUFREQ policy to control VLP governor (Rafael).

Signed-off-by: Francisco Jerez <currojerez at riseup.net>
Signed-off-by: Fengguang Wu <fengguang.wu at intel.com>
Signed-off-by: Julia Lawall <julia.lawall at lip6.fr>
---
 drivers/cpufreq/intel_pstate.c | 86 ++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 3daa9e057774..cb536b5a2d0d 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1031,6 +1031,88 @@ static void intel_pstate_update_limits(unsigned int cpu)
 	mutex_unlock(&intel_pstate_driver_lock);
 }
 
+/************************** debugfs begin ************************/
+static void intel_pstate_reset_vlp(struct cpudata *cpu);
+
+static int vlp_param_set(void *data, u64 val)
+{
+	unsigned int cpu;
+
+	*(u32 *)data = val;
+	for_each_possible_cpu(cpu) {
+		if (all_cpu_data[cpu])
+			intel_pstate_reset_vlp(all_cpu_data[cpu]);
+	}
+
+	WARN_ONCE(1, "Unsupported P-state VLP parameter update via debugging interface");
+
+	return 0;
+}
+
+static int vlp_param_get(void *data, u64 *val)
+{
+	*val = *(u32 *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_vlp_param, vlp_param_get, vlp_param_set,
+			 "%llu\n");
+
+static struct dentry *debugfs_parent;
+
+struct vlp_param {
+	char *name;
+	void *value;
+	struct dentry *dentry;
+};
+
+static struct vlp_param vlp_files[] = {
+	{"vlp_sample_interval_ms", &vlp_params.sample_interval_ms, },
+	{"vlp_setpoint_0_pml", &vlp_params.setpoint_0_pml, },
+	{"vlp_setpoint_aggr_pml", &vlp_params.setpoint_aggr_pml, },
+	{"vlp_avg_hz", &vlp_params.avg_hz, },
+	{"vlp_realtime_gain_pml", &vlp_params.realtime_gain_pml, },
+	{"vlp_debug", &vlp_params.debug, },
+	{NULL, NULL, }
+};
+
+static void intel_pstate_debug_expose_params(void)
+{
+	int i;
+
+	debugfs_parent = debugfs_create_dir("pstate_snb", NULL);
+	if (IS_ERR_OR_NULL(debugfs_parent))
+		return;
+
+	for (i = 0; vlp_files[i].name; i++) {
+		struct dentry *dentry;
+
+		dentry = debugfs_create_file_unsafe(vlp_files[i].name, 0660,
+						    debugfs_parent,
+						    vlp_files[i].value,
+						    &fops_vlp_param);
+		if (!IS_ERR(dentry))
+			vlp_files[i].dentry = dentry;
+	}
+}
+
+static void intel_pstate_debug_hide_params(void)
+{
+	int i;
+
+	if (IS_ERR_OR_NULL(debugfs_parent))
+		return;
+
+	for (i = 0; vlp_files[i].name; i++) {
+		debugfs_remove(vlp_files[i].dentry);
+		vlp_files[i].dentry = NULL;
+	}
+
+	debugfs_remove(debugfs_parent);
+	debugfs_parent = NULL;
+}
+
+/************************** debugfs end ************************/
+
 /************************** sysfs begin ************************/
 #define show_one(file_name, object)					\
 	static ssize_t show_##file_name					\
@@ -2977,6 +3059,8 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
 
 	global.min_perf_pct = min_perf_pct_min();
 
+	intel_pstate_debug_expose_params();
+
 	return 0;
 }
 
@@ -2985,6 +3069,8 @@ static int intel_pstate_unregister_driver(void)
 	if (hwp_active)
 		return -EBUSY;
 
+	intel_pstate_debug_hide_params();
+
 	cpufreq_unregister_driver(intel_pstate_driver);
 	intel_pstate_driver_cleanup();
 
-- 
2.20.1