[PATCH 1/2] PM / devfreq: Add debugfs support with devfreq_summary file

[Chanwoo Choi <cw00.choi@samsung.com>]

Add debugfs interface to provide debugging information of devfreq device.
It contains 'devfreq_summary' entry to show the summary of registered
devfreq devices as following and the additional debugfs file will be added.
- /sys/kernel/debug/devfreq/devfreq_summary

[Detailed description of each field of 'devfreq_summary' debugfs file]
- dev_name	: Device name of h/w.
- dev		: Device name made by devfreq core.
- parent_dev	: If devfreq device uses the passive governor,
		  show parent devfreq device name.
- governor	: Devfreq governor.
- polling_ms	: If devfreq device uses the simple_ondemand governor,
		  polling_ms is necessary for the period. (unit: millisecond)
- cur_freq_hz	: Current Frequency (unit: hz)
- old_freq_hz	: Frequency before changing. (unit: hz)
- new_freq_hz	: Frequency after changed. (unit: hz)

[For example on Exynos5422-based Odroid-XU3 board]
- In order to show the multiple governors on devfreq_summay result,
change the governor of devfreq0 from simple_ondemand to userspace.

$ cat /sys/kernel/debug/devfreq/devfreq_summary
dev_name                       dev        parent_dev governor        polling_ms cur_freq_hz  min_freq_hz  max_freq_hz
------------------------------ ---------- ---------- --------------- ---------- ------------ ------------ ------------
10c20000.memory-controller     devfreq0              userspace       0          206000000    165000000    825000000
soc:bus_wcore                  devfreq1              simple_ondemand 50         532000000    88700000     532000000
soc:bus_noc                    devfreq2   devfreq1   passive         0          111000000    66600000     111000000
soc:bus_fsys_apb               devfreq3   devfreq1   passive         0          222000000    111000000    222000000
soc:bus_fsys                   devfreq4   devfreq1   passive         0          200000000    75000000     200000000
soc:bus_fsys2                  devfreq5   devfreq1   passive         0          200000000    75000000     200000000
soc:bus_mfc                    devfreq6   devfreq1   passive         0          333000000    83250000     333000000
soc:bus_gen                    devfreq7   devfreq1   passive         0          266000000    88700000     266000000
soc:bus_peri                   devfreq8   devfreq1   passive         0          66600000     66600000     66600000
soc:bus_g2d                    devfreq9   devfreq1   passive         0          0            83250000     333000000
soc:bus_g2d_acp                devfreq10  devfreq1   passive         0          0            66500000     266000000
soc:bus_jpeg                   devfreq11  devfreq1   passive         0          0            75000000     300000000
soc:bus_jpeg_apb               devfreq12  devfreq1   passive         0          0            83250000     166500000
soc:bus_disp1_fimd             devfreq13  devfreq1   passive         0          0            120000000    200000000
soc:bus_disp1                  devfreq14  devfreq1   passive         0          0            120000000    300000000
soc:bus_gscl_scaler            devfreq15  devfreq1   passive         0          0            150000000    300000000
soc:bus_mscl                   devfreq16  devfreq1   passive         0          0            84000000     666000000

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/devfreq/devfreq.c | 80 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 254f11b31824..c7f5e4e06420 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/kmod.h>
 #include <linux/sched.h>
+#include <linux/debugfs.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -33,6 +34,7 @@
 #define HZ_PER_KHZ	1000
 
 static struct class *devfreq_class;
+static struct dentry *devfreq_debugfs;
 
 /*
  * devfreq core provides delayed work based load monitoring helper
@@ -1717,6 +1719,74 @@ static struct attribute *devfreq_attrs[] = {
 };
 ATTRIBUTE_GROUPS(devfreq);
 
+/**
+ * devfreq_summary_show() - Show the summary of the registered devfreq devices
+ *				via 'devfreq_summary' debugfs file.
+ */
+static int devfreq_summary_show(struct seq_file *s, void *data)
+{
+	struct devfreq *devfreq;
+	struct devfreq *p_devfreq = NULL;
+	unsigned long cur_freq, min_freq, max_freq;
+	unsigned int polling_ms;
+
+	seq_printf(s, "%-30s %-10s %-10s %-15s %-10s %-12s %-12s %-12s\n",
+			"dev_name",
+			"dev",
+			"parent_dev",
+			"governor",
+			"polling_ms",
+			"cur_freq_hz",
+			"min_freq_hz",
+			"max_freq_hz");
+	seq_printf(s, "%-30s %-10s %-10s %-15s %-10s %-12s %-12s %-12s\n",
+			"------------------------------",
+			"----------",
+			"----------",
+			"---------------",
+			"----------",
+			"------------",
+			"------------",
+			"------------");
+
+	mutex_lock(&devfreq_list_lock);
+
+	list_for_each_entry_reverse(devfreq, &devfreq_list, node) {
+#if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
+		if (!strncmp(devfreq->governor_name, DEVFREQ_GOV_PASSIVE,
+							DEVFREQ_NAME_LEN)) {
+			struct devfreq_passive_data *data = devfreq->data;
+
+			if (data)
+				p_devfreq = data->parent;
+		} else {
+			p_devfreq = NULL;
+		}
+#endif
+		mutex_lock(&devfreq->lock);
+		cur_freq = devfreq->previous_freq,
+		get_freq_range(devfreq, &min_freq, &max_freq);
+		polling_ms = devfreq->profile->polling_ms,
+		mutex_unlock(&devfreq->lock);
+
+		seq_printf(s,
+			"%-30s %-10s %-10s %-15s %-10d %-12ld %-12ld %-12ld\n",
+			dev_name(devfreq->dev.parent),
+			dev_name(&devfreq->dev),
+			p_devfreq ? dev_name(&p_devfreq->dev) : "",
+			devfreq->governor_name,
+			polling_ms,
+			cur_freq,
+			min_freq,
+			max_freq);
+	}
+
+	mutex_unlock(&devfreq_list_lock);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(devfreq_summary);
+
 static int __init devfreq_init(void)
 {
 	devfreq_class = class_create(THIS_MODULE, "devfreq");
@@ -1733,6 +1803,16 @@ static int __init devfreq_init(void)
 	}
 	devfreq_class->dev_groups = devfreq_groups;
 
+	devfreq_debugfs = debugfs_create_dir("devfreq", NULL);
+	if (PTR_ERR(devfreq_debugfs) != -ENODEV && IS_ERR(devfreq_debugfs)) {
+		devfreq_debugfs = NULL;
+		pr_warn("%s: couldn't create debugfs dir\n", __FILE__);
+	} else {
+		debugfs_create_file("devfreq_summary", 0444,
+				devfreq_debugfs, NULL,
+				&devfreq_summary_fops);
+	}
+
 	return 0;
 }
 subsys_initcall(devfreq_init);
-- 
2.17.1