[PATCH v2 2/2] acpi: battery: Handle Valve steamdeck devices quirk

[Umang Jain <uajain@igalia.com>]

Valve steamdeck devices can report battery status as
charging, even when low-powered power supply is connected
to the device. The battery status is reported as charging
through sysfs, even though in reality, it is discharging.

To handle this case, we introduce a battery quirk for steamdeck
devices ACPI_BATTERY_QUIRK_VALVE_STEAMDECK. Additionally, it has been
found that on such devices, Battery Charge Time ("_BCT") is reported
accurately, hence use that information for report charging vs
discharging status. Battery Charge Time("_BCT") with an eligible power
supply unit will have valid values whereas with a low-powered supply
unit, it shall report ACPI_BATTERY_VALUE_UNKNOWN. Use this as a
differentiator to determine, whether the battery of steamdeck devices
is really charging or not.

Signed-off-by: Umang Jain <uajain@igalia.com>
---
 drivers/acpi/battery.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index a1b7a821abaf..8defafd2b7c7 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -95,6 +95,14 @@ enum {
 	 * on a full charge, but showing degradation in full charge cap.
 	 */
 	ACPI_BATTERY_QUIRK_DEGRADED_FULL_CHARGE,
+	/*
+	 * Valve steamdeck devices can get discharged even when battery status
+	 * is charging. This happens typically when low power supply unit is
+	 * connected. To accurately determine this scenario, we shall read
+	 * battery charge time ("_BCT"). This is the key differentiator to
+	 * determine whether the steamdeck is actually charging or not.
+	 */
+	ACPI_BATTERY_QUIRK_VALVE_STEAMDECK,
 };
 
 struct acpi_battery {
@@ -236,7 +244,7 @@ static int acpi_battery_get_property(struct power_supply *psy,
 					: POWER_SUPPLY_STATUS_DISCHARGING;
 				return 0;
 			}
-		else if (battery->state & ACPI_BATTERY_STATE_CHARGING)
+		else if (battery->state & ACPI_BATTERY_STATE_CHARGING) {
 			/* Check the rate and capacity to validate the status. */
 			if (!acpi_battery_is_full(battery) ||
 			    (battery->rate_now != ACPI_BATTERY_VALUE_UNKNOWN &&
@@ -246,6 +254,12 @@ static int acpi_battery_get_property(struct power_supply *psy,
 				/* Full and zero rate. */
 				val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
 			}
+
+			if (test_bit(ACPI_BATTERY_QUIRK_VALVE_STEAMDECK, &battery->flags) &&
+			    test_bit(ACPI_BATTERY_BCT_PRESENT, &battery->flags) &&
+			    battery->charge_time == ACPI_BATTERY_VALUE_UNKNOWN)
+				val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		}
 		else if (battery->state & ACPI_BATTERY_STATE_CHARGE_LIMITING)
 			val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
 		else if (acpi_battery_is_charged(battery))
@@ -1072,6 +1086,18 @@ static void acpi_battery_quirks(struct acpi_battery *battery)
 		set_bit(ACPI_BATTERY_QUIRK_DEGRADED_FULL_CHARGE, &battery->flags);
 		battery->capacity_now = battery->full_charge_capacity;
 	}
+
+	if (test_bit(ACPI_BATTERY_QUIRK_VALVE_STEAMDECK, &battery->flags))
+		return;
+
+	if (dmi_name_in_vendors("Valve")) {
+		const char *name;
+
+		name = dmi_get_system_info(DMI_PRODUCT_NAME);
+		if ((name && (!strncmp("Jupiter", name, 7))) ||
+		    (name && (!strncmp("Galileo", name, 7))))
+			set_bit(ACPI_BATTERY_QUIRK_VALVE_STEAMDECK, &battery->flags);
+	}
 }
 
 static int acpi_battery_update(struct acpi_battery *battery, bool resume)
-- 
2.55.0