ACPI / battery: Ignore AC state in handle_discharging on systems where it is broken

On some devices the "AC" interface ACPI AML code uses the exact same broken
logic which is causing the battery code to wrongly report discharging to
determine the "AC" state. Specifically the ACPI AML code is checking the
charging status bits of the charger-IC rather then the vbus present or
power-good status bits.

This makes our workaround for devices which wrongly report discharging when
plugged into AC while the charge is above the start charging threshold not
work on these devices.

This commit adds a battery_ac_is_broken flag and when that is set it skips
the power_supply_is_system_supplied() check in the workaround fixing this.

This flag gets set by a DMI quirk selected by systems where we know the AC
AML code is broken in this way *and* the rate_now value can be trusted.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/battery.c

@@ -74,6 +74,7 @@ static async_cookie_t async_cookie;
 static bool battery_driver_registered;
 static int battery_bix_broken_package;
 static int battery_notification_delay_ms;
+static int battery_ac_is_broken;
 static unsigned int cache_time = 1000;
 module_param(cache_time, uint, 0644);
 MODULE_PARM_DESC(cache_time, "cache time in milliseconds");
@@ -222,7 +223,8 @@ static int acpi_battery_handle_discharging(struct acpi_battery *battery)
 	 * was above the device's start charging threshold atm the AC adapter
 	 * was plugged in and the device thus did not start a new charge cycle.
 	 */
-	if (power_supply_is_system_supplied() && battery->rate_now == 0)
+	if ((battery_ac_is_broken || power_supply_is_system_supplied()) &&
+	    battery->rate_now == 0)
 		return POWER_SUPPLY_STATUS_NOT_CHARGING;
 
 	return POWER_SUPPLY_STATUS_DISCHARGING;
@@ -1345,6 +1347,13 @@ battery_notification_delay_quirk(const struct dmi_system_id *d)
 	return 0;
 }
 
+static int __init
+battery_ac_is_broken_quirk(const struct dmi_system_id *d)
+{
+	battery_ac_is_broken = 1;
+	return 0;
+}
+
 static const struct dmi_system_id bat_dmi_table[] __initconst = {
 	{
 		/* NEC LZ750/LS */
@@ -1362,6 +1371,17 @@ static const struct dmi_system_id bat_dmi_table[] __initconst = {
 			DMI_MATCH(DMI_PRODUCT_NAME, "Aspire V5-573G"),
 		},
 	},
+	{
+		/* Point of View mobii wintab p800w */
+		.callback = battery_ac_is_broken_quirk,
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "AMI Corporation"),
+			DMI_MATCH(DMI_BOARD_NAME, "Aptio CRB"),
+			DMI_MATCH(DMI_BIOS_VERSION, "3BAIR1013"),
+			/* Above matches are too generic, add bios-date match */
+			DMI_MATCH(DMI_BIOS_DATE, "08/22/2014"),
+		},
+	},
 	{},
 };