linux-kernel - [PATCH][v3] PM / sleep: Add pm_debug

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Date:   Thu,  2 Apr 2020 15:56:52 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     linux-pm@...r.kernel.org
Cc:     Jonathan Corbet <corbet@....net>, Pavel Machek <pavel@....cz>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-doc@...r.kernel.org,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Chen Yu <yu.c.chen@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH][v3] PM / sleep: Add pm_debug_messages boot command control

Debug messages from the system suspend/hibernation infrastructure
is disabled by default, and can only be enabled after the system
has boot up via /sys/power/pm_debug_messages. This makes the hibernation
resume hard to track as it involves system boot up across hibernation.
There's no chance for software_resume() to track the resume process,
eg.

Turning on the pm_debug_messages during boot up by appending
'pm_debug_messages'.

Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Len Brown <lenb@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
v2: According to Randy's suggestion, add the command line
    option to Documentation/admin-guide/kernel-parameters.txt

v3: According to Rafael's suggestion, rename the boot command
    to pm_debug_messages
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 kernel/power/main.c                             | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ed73df5f1369..3fb9cbee8d28 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3720,6 +3720,9 @@
 			Override pmtimer IOPort with a hex value.
 			e.g. pmtmr=0x508
 
+	pm_debug_messages	[SUSPEND,KNL]
+			Enable suspend/resume debug messages during boot up.
+
 	pnp.debug=1	[PNP]
 			Enable PNP debug messages (depends on the
 			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 69b7a8aeca3b..40f86ec4ab30 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -535,6 +535,13 @@ static ssize_t pm_debug_messages_store(struct kobject *kobj,
 
 power_attr(pm_debug_messages);
 
+static int __init pm_debug_messages_setup(char *str)
+{
+	pm_debug_messages_on = true;
+	return 1;
+}
+__setup("pm_debug_messages", pm_debug_messages_setup);
+
 /**
  * __pm_pr_dbg - Print a suspend debug message to the kernel log.
  * @defer: Whether or not to use printk_deferred() to print the message.
-- 
2.17.1