PM / Suspend: Add statistics debugfs file for suspend to RAM

Record S3 failure time about each reason and the latest two failed
devices' names in S3 progress.
We can check it through 'suspend_stats' entry in debugfs.

The motivation of the patch:

We are enabling power features on Medfield. Comparing with PC/notebook,
a mobile enters/exits suspend-2-ram (we call it s3 on Medfield) far
more frequently. If it can't enter suspend-2-ram in time, the power
might be used up soon.

We often find sometimes, a device suspend fails. Then, system retries
s3 over and over again. As display is off, testers and developers
don't know what happens.

Some testers and developers complain they don't know if system
tries suspend-2-ram, and what device fails to suspend. They need
such info for a quick check. The patch adds suspend_stats under
debugfs for users to check suspend to RAM statistics quickly.

If not using this patch, we have other methods to get info about
what device fails. One is to turn on  CONFIG_PM_DEBUG, but users
would get too much info and testers need recompile the system.

In addition, dynamic debug is another good tool to dump debug info.
But it still doesn't match our utilization scenario closely.
1) user need write a user space parser to process the syslog output;
2) Our testing scenario is we leave the mobile for at least hours.
   Then, check its status. No serial console available during the
   testing. One is because console would be suspended, and the other
   is serial console connecting with spi or HSU devices would consume
   power. These devices are powered off at suspend-2-ram.

Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

2 files changed, 116 insertions, 3 deletions

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 6c601f871964..2757acba8e8a 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -12,6 +12,8 @@
 #include <linux/string.h>
 #include <linux/resume-trace.h>
 #include <linux/workqueue.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 #include "power.h"
 
@@ -133,6 +135,101 @@ power_attr(pm_test);
 
 #endif /* CONFIG_PM_SLEEP */
 
+#ifdef CONFIG_DEBUG_FS
+static char *suspend_step_name(enum suspend_stat_step step)
+{
+        switch (step) {
+        case SUSPEND_FREEZE:
+                return "freeze";
+        case SUSPEND_PREPARE:
+                return "prepare";
+        case SUSPEND_SUSPEND:
+                return "suspend";
+        case SUSPEND_SUSPEND_NOIRQ:
+                return "suspend_noirq";
+        case SUSPEND_RESUME_NOIRQ:
+                return "resume_noirq";
+        case SUSPEND_RESUME:
+                return "resume";
+        default:
+                return "";
+        }
+}
+
+static int suspend_stats_show(struct seq_file *s, void *unused)
+{
+        int i, index, last_dev, last_errno, last_step;
+
+        last_dev = suspend_stats.last_failed_dev + REC_FAILED_NUM - 1;
+        last_dev %= REC_FAILED_NUM;
+        last_errno = suspend_stats.last_failed_errno + REC_FAILED_NUM - 1;
+        last_errno %= REC_FAILED_NUM;
+        last_step = suspend_stats.last_failed_step + REC_FAILED_NUM - 1;
+        last_step %= REC_FAILED_NUM;
+        seq_printf(s, "%s: %d\n%s: %d\n%s: %d\n%s: %d\n"
+                        "%s: %d\n%s: %d\n%s: %d\n%s: %d\n",
+                        "success", suspend_stats.success,
+                        "fail", suspend_stats.fail,
+                        "failed_freeze", suspend_stats.failed_freeze,
+                        "failed_prepare", suspend_stats.failed_prepare,
+                        "failed_suspend", suspend_stats.failed_suspend,
+                        "failed_suspend_noirq",
+                                suspend_stats.failed_suspend_noirq,
+                        "failed_resume", suspend_stats.failed_resume,
+                        "failed_resume_noirq",
+                                suspend_stats.failed_resume_noirq);
+        seq_printf(s,   "failures:\n  last_failed_dev:\t%-s\n",
+                        suspend_stats.failed_devs[last_dev]);
+        for (i = 1; i < REC_FAILED_NUM; i++) {
+                index = last_dev + REC_FAILED_NUM - i;
+                index %= REC_FAILED_NUM;
+                seq_printf(s, "\t\t\t%-s\n",
+                        suspend_stats.failed_devs[index]);
+        }
+        seq_printf(s,   "  last_failed_errno:\t%-d\n",
+                        suspend_stats.errno[last_errno]);
+        for (i = 1; i < REC_FAILED_NUM; i++) {
+                index = last_errno + REC_FAILED_NUM - i;
+                index %= REC_FAILED_NUM;
+                seq_printf(s, "\t\t\t%-d\n",
+                        suspend_stats.errno[index]);
+        }
+        seq_printf(s,   "  last_failed_step:\t%-s\n",
+                        suspend_step_name(
+                                suspend_stats.failed_steps[last_step]));
+        for (i = 1; i < REC_FAILED_NUM; i++) {
+                index = last_step + REC_FAILED_NUM - i;
+                index %= REC_FAILED_NUM;
+                seq_printf(s, "\t\t\t%-s\n",
+                        suspend_step_name(
+                                suspend_stats.failed_steps[index]));
+        }
+
+        return 0;
+}
+
+static int suspend_stats_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, suspend_stats_show, NULL);
+}
+
+static const struct file_operations suspend_stats_operations = {
+        .open           = suspend_stats_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
+static int __init pm_debugfs_init(void)
+{
+        debugfs_create_file("suspend_stats", S_IFREG | S_IRUGO,
+                        NULL, NULL, &suspend_stats_operations);
+        return 0;
+}
+
+late_initcall(pm_debugfs_init);
+#endif /* CONFIG_DEBUG_FS */
+
 struct kobject *power_kobj;
 
 /**
@@ -194,6 +291,11 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
         }
         if (state < PM_SUSPEND_MAX && *s)
                 error = enter_state(state);
+                if (error) {
+                        suspend_stats.fail++;
+                        dpm_save_failed_errno(error);
+                } else
+                        suspend_stats.success++;
 #endif
 
  Exit:
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index b6b71ad2208f..595a3dd56a8a 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -104,7 +104,10 @@ static int suspend_prepare(void)
                 goto Finish;
 
         error = suspend_freeze_processes();
-        if (!error)
+        if (error) {
+                suspend_stats.failed_freeze++;
+                dpm_save_failed_step(SUSPEND_FREEZE);
+        } else
                 return 0;
 
         suspend_thaw_processes();
@@ -315,8 +318,16 @@ int enter_state(suspend_state_t state)
  */
 int pm_suspend(suspend_state_t state)
 {
-        if (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX)
-                return enter_state(state);
+        int ret;
+        if (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX) {
+                ret = enter_state(state);
+                if (ret) {
+                        suspend_stats.fail++;
+                        dpm_save_failed_errno(ret);
+                } else
+                        suspend_stats.success++;
+                return ret;
+        }
         return -EINVAL;
 }
 EXPORT_SYMBOL(pm_suspend);