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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 2 Apr 2020 15:33:45 +0200
Message-ID: <CAJZ5v0j2W5MYJnb4hiDn0OgR1xJZwm4TxVm9o-iw+epXPTp82g@mail.gmail.com>
Subject: Re: [PATCH][v3] PM / sleep: Add pm_debug_messages boot command control
To:     Chen Yu <yu.c.chen@intel.com>
Cc:     Linux PM <linux-pm@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>, Pavel Machek <pavel@ucw.cz>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Randy Dunlap <rdunlap@infradead.org>
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On Thu, Apr 2, 2020 at 9:58 AM Chen Yu <yu.c.chen@intel.com> wrote:
>
> 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@rjwysocki.net>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Signed-off-by: Chen Yu <yu.c.chen@intel.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.
> --

Applied (as 5.7-rc material) with modified subject and changelog, thanks!