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

[Rafael J. Wysocki (Intel)]

On Wed, Sep 23, 2026 at 10:28 AM Umang Jain <uajain@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> ---
>  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)

Would it be practical to evaluate _BCT here without storing
charge_time in the battery object?

> +                               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)
> --