[PATCH] ACPI: PM: s2idle: Invoke _PTS for s2idle

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

HP EliteBook 840 G8 reboots on s2idle resume, and HP EliteBook 845 G8
wakes up immediately on s2idle. Both are caused by the XMM7360 WWAN PCI
card.

There's a WWAN specific method to really turn off the WWAN via EC:
    Method (_PTS, 1, NotSerialized)  // _PTS: Prepare To Sleep
    {
    ...
        If (CondRefOf (\_SB.PCI0.GP12.PTS))
        {
            \_SB.PCI0.GP12.PTS (Arg0)
        }
    ...
    }

    Scope (_SB.PCI0.GP12)
    {
    ...
        Method (PTS, 1, Serialized)
        {
            If (^^LPCB.EC0.ECRG)
            {
                If ((PDID == 0xFFFF))
                {
                    Return (Zero)
                }

                POFF ()
                SGIO (WWBR, One)
                Sleep (0x1E)
                Acquire (^^LPCB.EC0.ECMX, 0xFFFF)
                ^^LPCB.EC0.WWP = One
                Release (^^LPCB.EC0.ECMX)
                Sleep (0x01F4)
            }

            Return (Zero)
        }
    ...
    }

So let's also invok _PTS for s2idle.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/acpi/sleep.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index 09fd13757b65..7e84b4b09919 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -698,6 +698,7 @@ int acpi_s2idle_prepare(void)
 	}
 
 	acpi_enable_wakeup_devices(ACPI_STATE_S0);
+	acpi_enter_sleep_state_prep(ACPI_STATE_S0);
 
 	/* Change the configuration of GPEs to avoid spurious wakeup. */
 	acpi_enable_all_wakeup_gpes();
-- 
2.30.2