linux-kernel - Re: [PATCH] ACPI: PM: Avoid removing power from unused hardware too early

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Message-ID: <CAJZ5v0hxzcxuQ596LncMKF-kTaOpfPXUFkKUt1GT3Cm4nR9yqw@mail.gmail.com>
Date:   Wed, 17 Nov 2021 17:10:20 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@....com>,
        "Kyle D. Pelton" <kyle.d.pelton@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] ACPI: PM: Avoid removing power from unused hardware too early

On Wed, Nov 10, 2021 at 8:53 PM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Commit c10383e8ddf4 ("ACPI: scan: Release PM resources blocked by
> unused objects") causes power to be removed from some hardware
> resources that appear to be unused too early, which leads to boot
> issues on some systems.
>
> To address this, move putting the unused ACPI device objects into
> D3cold to a late initcall.
>
> Fixes: c10383e8ddf4 ("ACPI: scan: Release PM resources blocked by unused objects")
> Reported-by: Kyle D. Pelton <kyle.d.pelton@...el.com>
> Tested-by: Kyle D. Pelton <kyle.d.pelton@...el.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Unfortunately, this fix is not effective in some cases, so I'm going
to revert commit c10383e8ddf4 for 5.16 and revisit this later.

Thanks!

> ---
>  drivers/acpi/scan.c |   22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
>
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -2559,12 +2559,6 @@ int __init acpi_scan_init(void)
>                 }
>         }
>
> -       /*
> -        * Make sure that power management resources are not blocked by ACPI
> -        * device objects with no users.
> -        */
> -       bus_for_each_dev(&acpi_bus_type, NULL, NULL, acpi_dev_turn_off_if_unused);
> -
>         acpi_turn_off_unused_power_resources();
>
>         acpi_scan_initialized = true;
> @@ -2574,6 +2568,22 @@ int __init acpi_scan_init(void)
>         return result;
>  }
>
> +static int acpi_turn_off_unused_devices(void)
> +{
> +       mutex_lock(&acpi_scan_lock);
> +
> +       /*
> +        * Make sure that power management resources are not blocked by ACPI
> +        * device objects with no users.
> +        */
> +       bus_for_each_dev(&acpi_bus_type, NULL, NULL, acpi_dev_turn_off_if_unused);
> +
> +       mutex_unlock(&acpi_scan_lock);
> +
> +       return 0;
> +}
> +late_initcall(acpi_turn_off_unused_devices);
> +
>  static struct acpi_probe_entry *ape;
>  static int acpi_probe_count;
>  static DEFINE_MUTEX(acpi_probe_mutex);
>
>
>