On Thu, Apr 12, 2018 at 4:01 AM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> On quite a few devices the battery code in the ACPI tables is buggy and
> first checks the charging status bits of the charger-IC, and if those
> report not charging it will report discharging, without looking at the
> presence of AC power or at the battery dis(charge) current from the
> fuel-gauge.
>
> This causes the wrong status to be reported for the battery in the
> following quite common scenario:
>
> 1) Plug in charger while battery is say half full, battery starts
> charging, charging state bits indicate: pre-charge or fast-charge,
> ACPI reported battery status is ok
>
> 2) When fully charged charging state bits indicate: end-of-charge,
> ACPI reported battery status is ok
>
> 3) unplug the charger, wait 1 minute, replug. Now the battery voltage is
> still above the start-charging threshold, so the charger will not start
> charging to avoid wrecking the battery by repeatedly recharging the last 1%
> capacity. The charger IC charging state bits now are all 0 (not-charging)
> and the broken ACPI code wrongly translate this to "discharging" and ends
> up setting the ACPI_BATTERY_STATE_DISCHARGING bit in its state field.
>
> Reporting this "not charging" state as discharging is confusing for users,
> making the user think his adapter/power-brick is broken or not properly
> plugged in.
>
> This commit adds a helper for handling the ACPI_BATTERY_STATE_DISCHARGING
> state. This helper checks if we're an AC and the current going out of the
> battery is 0 and in that case reports a status of "not charging" to
> userspace rather then "discharging".
>
> This replaces commit c68f0676ef7d ("ACPI / battery: Add quirk for Asus
> GL502VSK and UX305LA"), a previous fix for this which was reverted.
Reviewed-by: Daniel Drake <drake@xxxxxxxxxxxx>
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