linux-kernel - [PATCH] PM / sysfs: Expose suspend resume driver flags in sysfs

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Message-Id: <20201022032324.25308-1-yu.c.chen@intel.com>
Date:   Thu, 22 Oct 2020 11:23:24 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chen Yu <yu.c.chen@...el.com>
Subject: [PATCH] PM / sysfs: Expose suspend resume driver flags in sysfs

Currently there are 4 driver flags to control system suspend/resume
behavior: DPM_FLAG_NO_DIRECT_COMPLETE, DPM_FLAG_SMART_PREPARE,
DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP_RESUME. Make these flags
visible in sysfs as read-only to get a brief understanding of the
expected behavior of each device during suspend/resume, so as to
facilitate suspend/resume debugging/tuning.

For example:
/sys/devices/pci0000:00/0000:00:15.1/power/driver_flags:4
(DPM_FLAG_SMART_SUSPEND)

/sys/devices/pci0000:00/0000:00:07.3/power/driver_flags:5
(DPM_FLAG_NO_DIRECT_COMPLETE | DPM_FLAG_SMART_SUSPEND)

Acked-by: Len Brown <len.brown@...el.com>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
 drivers/base/power/sysfs.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index a1474fb67db9..48313a1040a5 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -607,6 +607,13 @@ static ssize_t async_store(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR_RW(async);
 
+static ssize_t driver_flags_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%x\n", dev->power.driver_flags);
+}
+static DEVICE_ATTR_RO(driver_flags);
+
 #endif /* CONFIG_PM_SLEEP */
 #endif /* CONFIG_PM_ADVANCED_DEBUG */
 
@@ -691,6 +698,20 @@ static const struct attribute_group pm_qos_flags_attr_group = {
 	.attrs	= pm_qos_flags_attrs,
 };
 
+static struct attribute *pm_driver_flags_attrs[] = {
+#ifdef CONFIG_PM_ADVANCED_DEBUG
+#ifdef CONFIG_PM_SLEEP
+	&dev_attr_driver_flags.attr,
+#endif
+#endif
+	NULL,
+};
+
+static const struct attribute_group pm_driver_flags_attr_group = {
+	.name	= power_group_name,
+	.attrs	= pm_driver_flags_attrs,
+};
+
 int dpm_sysfs_add(struct device *dev)
 {
 	int rc;
@@ -719,11 +740,17 @@ int dpm_sysfs_add(struct device *dev)
 		if (rc)
 			goto err_wakeup;
 	}
-	rc = pm_wakeup_source_sysfs_add(dev);
+	rc = sysfs_merge_group(&dev->kobj, &pm_driver_flags_attr_group);
 	if (rc)
 		goto err_latency;
+
+	rc = pm_wakeup_source_sysfs_add(dev);
+	if (rc)
+		goto err_flags;
 	return 0;
 
+ err_flags:
+	sysfs_unmerge_group(&dev->kobj, &pm_driver_flags_attr_group);
  err_latency:
 	sysfs_unmerge_group(&dev->kobj, &pm_qos_latency_tolerance_attr_group);
  err_wakeup:
-- 
2.17.1