linux-kernel - [PATCH] PM / reboot: Use S5 for reboot

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Message-Id: <20201030070659.16948-1-kai.heng.feng@canonical.com>
Date:   Fri, 30 Oct 2020 15:06:57 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     rafael.j.wysocki@...el.com
Cc:     hdegoede@...hat.com, linux-acpi@...r.kernel.org,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Petr Mladek <pmladek@...e.com>,
        Mike Rapoport <rppt@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] PM / reboot: Use S5 for reboot

After reboot, it's not possible to use hotkeys to enter BIOS setup and
boot menu on some HP laptops.

BIOS folks identified the root cause is the missing _PTS call, and BIOS
is expecting _PTS to do proper reset.

Using S5 for reboot is default behavior under Windows, "A full shutdown
(S5) occurs when a system restart is requested" [1], so let's do the
same here.

[1] https://docs.microsoft.com/en-us/windows/win32/power/system-power-states

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
 kernel/reboot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/reboot.c b/kernel/reboot.c
index e7b78d5ae1ab..7e5aa1f78693 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -244,6 +244,8 @@ void migrate_to_reboot_cpu(void)
 void kernel_restart(char *cmd)
 {
 	kernel_restart_prepare(cmd);
+	if (pm_power_off_prepare)
+		pm_power_off_prepare();
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	if (!cmd)
-- 
2.17.1