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

[Rafael J. Wysocki (Intel)]

On Fri, Sep 18, 2026 at 3:55 PM 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, first 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 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>

Please add _BCT support as a separate patch and the quirk on top of it.

Thanks!

> ---
>  drivers/acpi/battery.c | 42 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index 670853ec3a4d..db611f3302c4 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -76,6 +76,7 @@ MODULE_DEVICE_TABLE(acpi, battery_device_ids);
>  enum {
>         ACPI_BATTERY_ALARM_PRESENT,
>         ACPI_BATTERY_XINFO_PRESENT,
> +       ACPI_BATTERY_BCT_PRESENT,
>         ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY,
>         /* On Lenovo Thinkpad models from 2010 and 2011, the power unit
>          * switches between mWh and mAh depending on whether the system
> @@ -94,6 +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 low power supply unit is
> +        * connected. To accurate determine this scenario, we shall read
> +        * battery charge time ("_BCT") to know whether the steamdeck is
> +        * really charging with the power supply unit.
> +        */
> +       ACPI_BATTERY_QUIRK_VALVE_STEAMDECK,
>  };
>
>  struct acpi_battery {
> @@ -110,6 +119,7 @@ struct acpi_battery {
>
>         struct mutex property_lock; /* Protects properties below. */
>         unsigned long update_time;
> +       unsigned long long charge_time;
>         int revision;
>         int rate_now;
>         int capacity_now;
> @@ -234,7 +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 &&
> @@ -244,6 +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))
> @@ -613,6 +629,10 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
>         int result = 0;
>         acpi_status status = 0;
>         struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +       union acpi_object arg0 = { ACPI_TYPE_INTEGER };
> +       struct acpi_object_list args = { 1, &arg0 };
> +
> +       arg0.integer.value = 100;
>
>         lockdep_assert_held(&battery->property_lock);
>
> @@ -638,6 +658,15 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
>         battery->update_time = jiffies;
>         kfree(buffer.pointer);
>
> +       if (test_bit(ACPI_BATTERY_BCT_PRESENT, &battery->flags)) {
> +               status = acpi_evaluate_integer(battery->device->handle, "_BCT",
> +                                              &args, &battery->charge_time);
> +               if (ACPI_FAILURE(status))
> +                       acpi_handle_info(battery->device->handle,
> +                                        "_BCT evaluation failed: %s",
> +                                        acpi_format_exception(status));
> +       }
> +
>         /* For buggy DSDTs that report negative 16-bit values for either
>          * charging or discharging current and/or report 0 as 65536
>          * due to bad math.
> @@ -1057,6 +1086,15 @@ 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 (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)
> @@ -1083,6 +1121,8 @@ static int acpi_battery_update(struct acpi_battery *battery, bool resume)
>                         if (result)
>                                 return result;
>                         acpi_battery_init_alarm(battery);
> +                       if (acpi_has_method(battery->device->handle, "_BCT"))
> +                               set_bit(ACPI_BATTERY_BCT_PRESENT, &battery->flags);
>                 }
>
>                 result = acpi_battery_get_state(battery);
> --
> 2.55.0
>