PM / devfreq: Add sysfs node for representing frequency transition information.

This patch adds sysfs node which can be used to get information of frequency
transition. It represents transition table which contains total number of transition of
each freqeuncy state and time spent. It is inspired CPUFREQ's status driver.

Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
[Added Documentation/ABI entry, updated kernel-doc, and resolved merge conflict]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

1 files changed, 101 insertions, 0 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index c44e562bdfe0..bf6de38190cf 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -66,6 +66,51 @@ static struct devfreq *find_device_devfreq(struct device *dev)
         return ERR_PTR(-ENODEV);
 }
 
+/**
+ * devfreq_get_freq_level() - Lookup freq_table for the frequency
+ * @devfreq:    the devfreq instance
+ * @freq:       the target frequency
+ */
+static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
+{
+        int lev;
+
+        for (lev = 0; lev < devfreq->profile->max_state; lev++)
+                if (freq == devfreq->profile->freq_table[lev])
+                        return lev;
+
+        return -EINVAL;
+}
+
+/**
+ * devfreq_update_status() - Update statistics of devfreq behavior
+ * @devfreq:    the devfreq instance
+ * @freq:       the update target frequency
+ */
+static int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
+{
+        int lev, prev_lev;
+        unsigned long cur_time;
+
+        lev = devfreq_get_freq_level(devfreq, freq);
+        if (lev < 0)
+                return lev;
+
+        cur_time = jiffies;
+        devfreq->time_in_state[lev] +=
+                         cur_time - devfreq->last_stat_updated;
+        if (freq != devfreq->previous_freq) {
+                prev_lev = devfreq_get_freq_level(devfreq,
+                                                devfreq->previous_freq);
+                devfreq->trans_table[(prev_lev *
+                                devfreq->profile->max_state) + lev]++;
+                devfreq->total_trans++;
+        }
+        devfreq->last_stat_updated = cur_time;
+
+        return 0;
+}
+
 /* Load monitoring helper functions for governors use */
 
 /**
@@ -112,6 +157,11 @@ int update_devfreq(struct devfreq *devfreq)
         if (err)
                 return err;
 
+        if (devfreq->profile->freq_table)
+                if (devfreq_update_status(devfreq, freq))
+                        dev_err(&devfreq->dev,
+                                "Couldn't update frequency transition information.\n");
+
         devfreq->previous_freq = freq;
         return err;
 }
@@ -378,6 +428,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
         devfreq->data = data;
         devfreq->nb.notifier_call = devfreq_notifier_call;
 
+        devfreq->trans_table =  devm_kzalloc(dev, sizeof(unsigned int) *
+                                                devfreq->profile->max_state *
+                                                devfreq->profile->max_state,
+                                                GFP_KERNEL);
+        devfreq->time_in_state = devm_kzalloc(dev, sizeof(unsigned int) *
+                                                devfreq->profile->max_state,
+                                                GFP_KERNEL);
+        devfreq->last_stat_updated = jiffies;
+
         dev_set_name(&devfreq->dev, dev_name(dev));
         err = device_register(&devfreq->dev);
         if (err) {
@@ -601,6 +660,47 @@ static ssize_t show_available_freqs(struct device *d,
         return count;
 }
 
+static ssize_t show_trans_table(struct device *dev, struct device_attribute *attr,
+                                char *buf)
+{
+        struct devfreq *devfreq = to_devfreq(dev);
+        ssize_t len;
+        int i, j, err;
+        unsigned int max_state = devfreq->profile->max_state;
+
+        err = devfreq_update_status(devfreq, devfreq->previous_freq);
+        if (err)
+                return 0;
+
+        len = sprintf(buf, "   From  :   To\n");
+        len += sprintf(buf + len, "         :");
+        for (i = 0; i < max_state; i++)
+                len += sprintf(buf + len, "%8u",
+                                devfreq->profile->freq_table[i]);
+
+        len += sprintf(buf + len, "   time(ms)\n");
+
+        for (i = 0; i < max_state; i++) {
+                if (devfreq->profile->freq_table[i]
+                                        == devfreq->previous_freq) {
+                        len += sprintf(buf + len, "*");
+                } else {
+                        len += sprintf(buf + len, " ");
+                }
+                len += sprintf(buf + len, "%8u:",
+                                devfreq->profile->freq_table[i]);
+                for (j = 0; j < max_state; j++)
+                        len += sprintf(buf + len, "%8u",
+                                devfreq->trans_table[(i * max_state) + j]);
+                len += sprintf(buf + len, "%10u\n",
+                        jiffies_to_msecs(devfreq->time_in_state[i]));
+        }
+
+        len += sprintf(buf + len, "Total transition : %u\n",
+                                        devfreq->total_trans);
+        return len;
+}
+
 static struct device_attribute devfreq_attrs[] = {
         __ATTR(governor, S_IRUGO, show_governor, NULL),
         __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
@@ -610,6 +710,7 @@ static struct device_attribute devfreq_attrs[] = {
                store_polling_interval),
         __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
         __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
+        __ATTR(trans_stat, S_IRUGO, show_trans_table, NULL),
         { },
 };