ACPI / battery: fix wrong value of capacity_now reported when fully charged

It seems that some batteries (noticed on DELL JYPJ136) assume
capacity_now = design_capacity when fully charged. This causes
reported capacity to suddenly jump to >full_charge_capacity (and that
means capacity reported to userspace is >100% and incorrect)
values after 99%. This patch detects capacity_now > full_charge_capacity,
notifies userspace (unless it is the known bug where capacity_now ==
design_capacity) and trims the value to full_charge_capacity.

Signed-off-by: Josef Gajdusek <atx@atx.name>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index bc0b286ff2ba..130f513e08c9 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -535,6 +535,20 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
                         " invalid.\n");
         }
 
+        /*
+         * When fully charged, some batteries wrongly report
+         * capacity_now = design_capacity instead of = full_charge_capacity
+         */
+        if (battery->capacity_now > battery->full_charge_capacity
+            && battery->full_charge_capacity != ACPI_BATTERY_VALUE_UNKNOWN) {
+                battery->capacity_now = battery->full_charge_capacity;
+                if (battery->capacity_now != battery->design_capacity)
+                        printk_once(KERN_WARNING FW_BUG
+                                "battery: reported current charge level (%d) "
+                                "is higher than reported maximum charge level (%d).\n",
+                                battery->capacity_now, battery->full_charge_capacity);
+        }
+
         if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)
             && battery->capacity_now >= 0 && battery->capacity_now <= 100)
                 battery->capacity_now = (battery->capacity_now *