[PATCH 1/3] thinkpad_acpi: add support for force_discharge

[Nicolo' Piazzalunga <nicolopiazzalunga@gmail.com>]

Lenovo ThinkPad systems have a feature that lets you
force the battery to discharge when AC is attached.

This patch implements that feature and exposes it via the generic
ACPI battery driver in the generic location:

/sys/class/power_supply/BATx/force_discharge

Signed-off-by: Ognjen Galic <smclt30p@gmail.com>
Signed-off-by: Thomas Koch <linrunner@gmx.net>
Signed-off-by: Nicolo' Piazzalunga <nicolopiazzalunga@gmail.com>
---
 drivers/platform/x86/thinkpad_acpi.c | 59 ++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 9c4df41687a3..6c7dca3a10d2 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -9317,6 +9317,8 @@ static struct ibm_struct mute_led_driver_data = {
 #define SET_START	"BCCS"
 #define GET_STOP	"BCSG"
 #define SET_STOP	"BCSS"
+#define GET_DISCHARGE	"BDSG"
+#define SET_DISCHARGE	"BDSS"
 
 enum {
 	BAT_ANY = 0,
@@ -9333,6 +9335,7 @@ enum {
 	/* This is used in the get/set helpers */
 	THRESHOLD_START,
 	THRESHOLD_STOP,
+	FORCE_DISCHARGE
 };
 
 struct tpacpi_battery_data {
@@ -9340,6 +9343,7 @@ struct tpacpi_battery_data {
 	int start_support;
 	int charge_stop;
 	int stop_support;
+	int discharge_support;
 };
 
 struct tpacpi_battery_driver_data {
@@ -9397,6 +9401,12 @@ static int tpacpi_battery_get(int what, int battery, int *ret)
 		if (*ret == 0)
 			*ret = 100;
 		return 0;
+	case FORCE_DISCHARGE:
+		if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, ret, battery))
+			return -ENODEV;
+		/* The force discharge status is in bit 0 */
+		*ret = *ret & 0x01;
+		return 0;
 	default:
 		pr_crit("wrong parameter: %d", what);
 		return -EINVAL;
@@ -9425,6 +9435,16 @@ static int tpacpi_battery_set(int what, int battery, int value)
 			return -ENODEV;
 		}
 		return 0;
+	case FORCE_DISCHARGE:
+		/* Force discharge is in bit 0,
+		 * break on AC attach is in bit 1 (won't work on some ThinkPads),
+		 * battery ID is in bits 8-9, 2 bits.
+		 */
+		if ACPI_FAILURE(tpacpi_battery_acpi_eval(SET_DISCHARGE, &ret, param)) {
+			pr_err("failed to set force dischrage on %d", battery);
+			return -ENODEV;
+		}
+		return 0;
 	default:
 		pr_crit("wrong parameter: %d", what);
 		return -EINVAL;
@@ -9443,6 +9463,8 @@ static int tpacpi_battery_probe(int battery)
 	 * 2) Check for support
 	 * 3) Get the current stop threshold
 	 * 4) Check for support
+	 * 5) Get the current force discharge status
+	 * 6) Check for support
 	 */
 	if (acpi_has_method(hkey_handle, GET_START)) {
 		if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_START, &ret, battery)) {
@@ -9479,11 +9501,16 @@ static int tpacpi_battery_probe(int battery)
 			return -ENODEV;
 		}
 	}
-	pr_info("battery %d registered (start %d, stop %d)",
+	if (acpi_has_method(hkey_handle, GET_DISCHARGE))
+		if (!ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, &ret, battery)))
+			/* Support is marked in bit 8 */
+			battery_info.batteries[battery].discharge_support = ret & BIT(8);
+
+	pr_info("battery %d registered (start %d, stop %d, force: %d)",
 			battery,
 			battery_info.batteries[battery].charge_start,
-			battery_info.batteries[battery].charge_stop);
-
+			battery_info.batteries[battery].charge_stop,
+			battery_info.batteries[battery].discharge_support);
 	return 0;
 }
 
@@ -9569,6 +9596,15 @@ static ssize_t tpacpi_battery_store(int what,
 		if (tpacpi_battery_set(THRESHOLD_STOP, battery, value))
 			return -EINVAL;
 		return count;
+	case FORCE_DISCHARGE:
+		if (!battery_info.batteries[battery].discharge_support)
+			return -ENODEV;
+		/* The only valid values are 1 and 0 */
+		if (value != 0 && value != 1)
+			return -EINVAL;
+		if (tpacpi_battery_set(FORCE_DISCHARGE, battery, value))
+			return -ENODEV;
+		return count;
 	default:
 		pr_crit("Wrong parameter: %d", what);
 		return -EINVAL;
@@ -9617,6 +9653,13 @@ static ssize_t charge_control_end_threshold_show(struct device *device,
 	return tpacpi_battery_show(THRESHOLD_STOP, device, buf);
 }
 
+static ssize_t force_discharge_show(struct device *device,
+				struct device_attribute *attr,
+				char *buf)
+{
+	return tpacpi_battery_show(FORCE_DISCHARGE, device, buf);
+}
+
 static ssize_t charge_control_start_threshold_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
@@ -9631,8 +9674,16 @@ static ssize_t charge_control_end_threshold_store(struct device *dev,
 	return tpacpi_battery_store(THRESHOLD_STOP, dev, buf, count);
 }
 
+static ssize_t force_discharge_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	return tpacpi_battery_store(FORCE_DISCHARGE, dev, buf, count);
+}
+
 static DEVICE_ATTR_RW(charge_control_start_threshold);
 static DEVICE_ATTR_RW(charge_control_end_threshold);
+static DEVICE_ATTR_RW(force_discharge);
 static struct device_attribute dev_attr_charge_start_threshold = __ATTR(
 	charge_start_threshold,
 	0644,
@@ -9645,12 +9696,12 @@ static struct device_attribute dev_attr_charge_stop_threshold = __ATTR(
 	charge_control_end_threshold_show,
 	charge_control_end_threshold_store
 );
-
 static struct attribute *tpacpi_battery_attrs[] = {
 	&dev_attr_charge_control_start_threshold.attr,
 	&dev_attr_charge_control_end_threshold.attr,
 	&dev_attr_charge_start_threshold.attr,
 	&dev_attr_charge_stop_threshold.attr,
+	&dev_attr_force_discharge.attr,
 	NULL,
 };
 
-- 
2.25.1