Pasting in for completeness since this started as a mail thread. -------- Original Message -------- Subject: [Fwd: [patch 1/9] acpi battery: work around negative s16 battery current on Acer] Date: Mon, 31 Aug 2009 14:09:22 +0200 From: Stefan Bader To: Pete Graner Hi Pete, while walking over the linux-acpi list, this has been just accepted and it looks pretty much like fitting. From your acpi dump I see it is using mA and does a calculation which takes a 16bit value from the EC and then subtracts 65536 from that. Though that should not directly cause a battery critical warning (this is stored in another bit of the EC), but maybe gnome power manager tries to be smart about the discharge rate. It might be an interesting experiment to have the battery info logged in a tight loop and then unplug ac. At least a bit of it should make it to disk before suspending. -Stefan -------- Original Message -------- Subject: [patch 1/9] acpi battery: work around negative s16 battery current on Acer Date: Thu, 06 Aug 2009 15:57:48 -0700 From: To: CC: , , , From: Hector Martin Acer Aspire 8930G laptops (and possibly others) report the battery current as a 16-bit signed negative when it is charging. It also reports it as 0x10000 when the current is 0. This patch adds a quirk for this which takes the absolute value of the reported current cast to an s16. This is a DSDT bug present in the latest BIOS revision (the EC register is 16 bits signed and the DSDT attempts to take the 16-bit two's complement of this, which works for discharge but not charge. It also breaks zero values because a 32-bit register is used and the high bits aren't thrown away). I've enabled this for all Acer systems which report in mA units. This should be safe since it won't break compliant systems unless they report a current above 32A, which is insane. The patch also detects the valid 32-bit value -1, which indicates unknown status, and does not attempt the fix in that case (note that this does not conflict with 16-bit -1, which is 65535 as read normally and gets translated to 1mA). Signed-off-by: Hector Martin Cc: Alexey Starikovskiy Cc: Len Brown Signed-off-by: Andrew Morton --- drivers/acpi/battery.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff -puN drivers/acpi/battery.c~acpi-battery-work-around-negative-s16-battery-current-on-acer drivers/acpi/battery.c --- a/drivers/acpi/battery.c~acpi-battery-work-around-negative-s16-battery-current-on-acer +++ a/drivers/acpi/battery.c @@ -85,6 +85,10 @@ static const struct acpi_device_id batte MODULE_DEVICE_TABLE(acpi, battery_device_ids); +/* 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. + */ +#define QUIRK_SIGNED16_CURRENT 0x0001 struct acpi_battery { struct mutex lock; @@ -112,6 +116,7 @@ struct acpi_battery { int state; int power_unit; u8 alarm_present; + long quirks; }; #define to_acpi_battery(x) container_of(x, struct acpi_battery, bat); @@ -390,6 +395,11 @@ static int acpi_battery_get_state(struct state_offsets, ARRAY_SIZE(state_offsets)); battery->update_time = jiffies; kfree(buffer.pointer); + + if ((battery->quirks & QUIRK_SIGNED16_CURRENT) && + battery->rate_now != -1) + battery->rate_now = abs((s16)battery->rate_now); + return result; } @@ -495,6 +505,14 @@ static void sysfs_remove_battery(struct } #endif +static void acpi_battery_quirks(struct acpi_battery *battery) +{ + battery->quirks = 0; + if (dmi_name_in_vendors("Acer") && battery->power_unit) { + battery->quirks |= QUIRK_SIGNED16_CURRENT; + } +} + static int acpi_battery_update(struct acpi_battery *battery) { int result, old_present = acpi_battery_present(battery); @@ -513,6 +531,7 @@ static int acpi_battery_update(struct ac result = acpi_battery_get_info(battery); if (result) return result; + acpi_battery_quirks(battery); acpi_battery_init_alarm(battery); } #ifdef CONFIG_ACPI_SYSFS_POWER _ -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to