[PATCH 1/1] UBUNTU: SAUCE: Revert "rtc: rtc-cmos: Do not check ACPI_FADT_LOW_POWER_S0"

[Cory Todd]

BugLink: https://bugs.launchpad.net/bugs/2011854

This reverts commit f2a7f3238777b8061d926ba3c34c232ffa212e6a.

On Oracle cloud, ACPI alarm and update interrupts are not generated by the
CMOS RTC on the following instance types:

- VM.DenseIO2.8
- VM.Standard2.1

Prior to this commit, these instance types were depending on HPET for
these interrupts. Removing the check for an unset ACPI_FADT_LOW_POWER_S0
in use_acpi_alarm_quirks() disables the use of HPET on these instance
types. This leaves acpi_alarm_mode responsible for alarm and update
interrupts. The acpi_alarm_mode on these instance types is broken so
let's keep the quirk in place as a conservative way to continue using
HPET for these interrupts.

Signed-off-by: Cory Todd <cory.todd at canonical.com>
---
 drivers/rtc/rtc-cmos.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 00e2ca7374ec..0fc9b127c011 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -824,6 +824,9 @@ static void use_acpi_alarm_quirks(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 		return;
 
+	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
+		return;
+
 	if (!is_hpet_enabled())
 		return;
 
-- 
2.40.0