[ Note: this is a follow-up on https://bugzilla.kernel.org/show_bug.cgi?id=41062 ] Please find below a patch to drivers/acpi/battery.c that adds a quirk to correctly report battery capacity on recent Lenovo Thinkpad models. The 2010 and 2011 Thinkpad models that I tested (x201, t410, t410s, and x220) exhibit a problem where, when battery capacity reporting unit is mAh, the values being reported are wrong. For some reason, these Thinkpads switch the reporting unit between mAh and mWh; generally, mAh is used when a laptop is plugged in and mWh when it's unplugged, although a suspend/resume or rmmod/modprobe is needed for the switch to take an effect. Anyway, the values reported in mAh are *always* wrong. I tested back to kernel 2.6.34, with multiple machines and BIOS versions. Simply plugging a laptop into mains before turning it on is enough to reproduce the problem. Here's a sample /proc/acpi/battery/BAT0/info from Thinkpad x220 with a 4-cell battery: present: yes design capacity: 2886 mAh last full capacity: 2909 mAh battery technology: rechargeable design voltage: 14800 mV design capacity warning: 145 mAh design capacity low: 13 mAh cycle count: 0 capacity granularity 1: 1 mAh capacity granularity 2: 1 mAh model number: 42T4899 serial number: 21064 battery type: LION OEM info: SANYO Once the laptop switches the unit to mWh, the output changes to: present: yes design capacity: 28860 mWh last full capacity: 29090 mWh battery technology: rechargeable design voltage: 14800 mV design capacity warning: 1454 mWh design capacity low: 200 mWh cycle count: 0 capacity granularity 1: 1 mWh capacity granularity 2: 1 mWh model number: 42T4899 serial number: 21064 battery type: LION OEM info: SANYO Can you see how the values for "design capacity", etc., differ by a factor of 10 instead of 14.8 (the design voltage of this battery)? On the battery itself it says: 14.8V, 1.95Ah, 29Wh, so clearly the values reported in mWh are correct and the ones in mAh are not. My guess is that this problem has been around ever since those machines have been released, but because the most common Thinkpad batteries are rated at 10.8V, the error (8%) is small enough that it simply hasn't been noticed or at least nobody could be bothered to look into it. Pre-2010 Thinkpads (tested with t42, t61, t500, x200, x300) appear to always report in mWh, so they should be fine. My patch works around the problem by adjusting the incorrectly reported mAh values by "10000 / design_voltage". The patch also has code to figure out if it should be activated or not. The patch only activates on Lenovo Thinkpads, and only when the battery capacity reported through ACPI does not match what is reported through DMI. It should thus be safe on all machines, including future models. I've been using this patch for sever months on several systems without any problems. I believe it is ready to be applied, although I lack kernel hacking experience to make that determination. Obviously, a better solution would be to somehow force the machines to always report the battery capacity in mWh, which does not require correction and would thus make this patch unnecessary, but I have no idea how to do that or if it is even possible at all. Note that I'm not on the list so I would appreciate a Cc on any replies. I will also try to monitor the list archives. Kamil Iskra --- battery.c.orig 2011-08-08 21:47:15.812854942 -0500 +++ battery.c 2011-09-03 23:16:02.203031764 -0500 @@ -34,6 +34,7 @@ #include <linux/dmi.h> #include <linux/slab.h> #include <linux/suspend.h> +#include <asm/unaligned.h> #ifdef CONFIG_ACPI_PROCFS_POWER #include <linux/proc_fs.h> @@ -95,6 +96,14 @@ enum { ACPI_BATTERY_ALARM_PRESENT, ACPI_BATTERY_XINFO_PRESENT, ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, + /* Starting with the 2010 Lenovo Thinkpad models, the power unit + switches between mWh and mAh depending on whether the system + is running on battery or not. When mAh is the unit, most + reported values are incorrect and need to be adjusted by + 10000/design_voltage. Verified on x201, t410, t410s, and x220. + It appears that the pre-2010 Thinkpads always report in mWh and + are thus unaffected (tested with t42, t61, t500, x200, x300). */ + ACPI_BATTERY_QUIRK_THINKPAD_MAH, }; struct acpi_battery { @@ -429,6 +438,21 @@ static int acpi_battery_get_info(struct kfree(buffer.pointer); if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)) battery->full_charge_capacity = battery->design_capacity; + if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags) && + battery->power_unit && battery->design_voltage) { + battery->design_capacity = battery->design_capacity * + 10000 / battery->design_voltage; + battery->full_charge_capacity = battery->full_charge_capacity * + 10000 / battery->design_voltage; + battery->design_capacity_warning = + battery->design_capacity_warning * + 10000 / battery->design_voltage; + /* Curiously, design_capacity_low, unlike the rest of them, + is correct. */ + /* capacity_granularity_* equal 1 on the systems tested, so + it's impossible to tell if they would need an adjustment + or not if their values were higher. */ + } return result; } @@ -477,6 +501,11 @@ static int acpi_battery_get_state(struct && battery->capacity_now >= 0 && battery->capacity_now <= 100) battery->capacity_now = (battery->capacity_now * battery->full_charge_capacity) / 100; + if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags) && + battery->power_unit && battery->design_voltage) { + battery->capacity_now = battery->capacity_now * + 10000 / battery->design_voltage; + } return result; } @@ -586,6 +615,24 @@ static void sysfs_remove_battery(struct mutex_unlock(&battery->sysfs_lock); } +static void find_battery(const struct dmi_header *dm, void *private) +{ + struct acpi_battery *battery = (struct acpi_battery *)private; + /* Note: the hardcoded offsets below have been extracted from + the source code of dmidecode. */ + if (dm->type == DMI_ENTRY_PORTABLE_BATTERY && dm->length >= 8) { + const u8 *dmi_data = (const u8 *)(dm + 1); + int dmi_capacity = get_unaligned((const u16 *)(dmi_data + 6)); + if (dm->length >= 18) + dmi_capacity *= dmi_data[17]; + if (battery->design_capacity * battery->design_voltage / 1000 + != dmi_capacity && + battery->design_capacity * 10 == dmi_capacity) + set_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, + &battery->flags); + } +} + /* * According to the ACPI spec, some kinds of primary batteries can * report percentage battery remaining capacity directly to OS. @@ -611,6 +658,32 @@ static void acpi_battery_quirks(struct a battery->capacity_now = (battery->capacity_now * battery->full_charge_capacity) / 100; } + + if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags)) + return ; + + if (battery->power_unit && dmi_name_in_vendors("LENOVO")) { + const char *s; + s = dmi_get_system_info(DMI_PRODUCT_VERSION); + if (s && !strnicmp(s, "ThinkPad", 8)) { + dmi_walk(find_battery, battery); + if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, + &battery->flags) && + battery->design_voltage) { + battery->design_capacity = + battery->design_capacity * + 10000 / battery->design_voltage; + battery->full_charge_capacity = + battery->full_charge_capacity * + 10000 / battery->design_voltage; + battery->design_capacity_warning = + battery->design_capacity_warning * + 10000 / battery->design_voltage; + battery->capacity_now = battery->capacity_now * + 10000 / battery->design_voltage; + } + } + } } static int acpi_battery_update(struct acpi_battery *battery) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
