diff --git a/MAINTAINERS b/MAINTAINERS
index d756b9ec236d..f44521abe8bf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11861,6 +11861,13 @@ F:	drivers/scsi/smartpqi/smartpqi*.[ch]
 F:	include/linux/cciss*.h
 F:	include/uapi/linux/cciss*.h
 
+MICROSOFT SURFACE BATTERY AND AC DRIVERS
+M:	Maximilian Luz <luzmaximilian@gmail.com>
+L:	linux-pm@vger.kernel.org
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/power/supply/surface_battery.c
+
 MICROSOFT SURFACE GPE LID SUPPORT DRIVER
 M:	Maximilian Luz <luzmaximilian@gmail.com>
 L:	platform-driver-x86@vger.kernel.org
diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 006b95eca673..cebeff10d543 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -801,4 +801,20 @@ config BATTERY_ACER_A500
 	help
 	  Say Y to include support for Acer Iconia Tab A500 battery fuel gauge.
 
+config BATTERY_SURFACE
+	tristate "Battery driver for 7th-generation Microsoft Surface devices"
+	depends on SURFACE_AGGREGATOR_REGISTRY
+	help
+	  Driver for battery devices connected via/managed by the Surface System
+	  Aggregator Module (SSAM).
+
+	  This driver provides battery-information and -status support for
+	  Surface devices where said data is not exposed via the standard ACPI
+	  devices. On those models (7th-generation), battery-information is
+	  instead handled directly via SSAM client devices and this driver.
+
+	  Say M or Y here to include battery status support for 7th-generation
+	  Microsoft Surface devices, i.e. Surface Pro 7, Surface Laptop 3,
+	  Surface Book 3, and Surface Laptop Go.
+
 endif # POWER_SUPPLY
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 5e5fdbbef531..134041538d2c 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -101,3 +101,4 @@ obj-$(CONFIG_CHARGER_BD99954)	+= bd99954-charger.o
 obj-$(CONFIG_CHARGER_WILCO)	+= wilco-charger.o
 obj-$(CONFIG_RN5T618_POWER)	+= rn5t618_power.o
 obj-$(CONFIG_BATTERY_ACER_A500)	+= acer_a500_battery.o
+obj-$(CONFIG_BATTERY_SURFACE)	+= surface_battery.o
diff --git a/drivers/power/supply/surface_battery.c b/drivers/power/supply/surface_battery.c
new file mode 100644
index 000000000000..b93a4f556b5c
--- /dev/null
+++ b/drivers/power/supply/surface_battery.c
@@ -0,0 +1,901 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Battery driver for 7th-generation Microsoft Surface devices via Surface
+ * System Aggregator Module (SSAM).
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/power_supply.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include <linux/surface_aggregator/device.h>
+
+
+/* -- SAM interface. -------------------------------------------------------- */
+
+enum sam_event_cid_bat {
+	SAM_EVENT_CID_BAT_BIX         = 0x15,
+	SAM_EVENT_CID_BAT_BST         = 0x16,
+	SAM_EVENT_CID_BAT_ADP         = 0x17,
+	SAM_EVENT_CID_BAT_PROT        = 0x18,
+	SAM_EVENT_CID_BAT_DPTF        = 0x53,
+};
+
+enum sam_battery_sta {
+	SAM_BATTERY_STA_OK            = 0x0f,
+	SAM_BATTERY_STA_PRESENT	      = 0x10,
+};
+
+enum sam_battery_state {
+	SAM_BATTERY_STATE_DISCHARGING = BIT(0),
+	SAM_BATTERY_STATE_CHARGING    = BIT(1),
+	SAM_BATTERY_STATE_CRITICAL    = BIT(2),
+};
+
+enum sam_battery_power_unit {
+	SAM_BATTERY_POWER_UNIT_mW     = 0,
+	SAM_BATTERY_POWER_UNIT_mA     = 1,
+};
+
+/* Equivalent to data returned in ACPI _BIX method, revision 0. */
+struct spwr_bix {
+	u8  revision;
+	__le32 power_unit;
+	__le32 design_cap;
+	__le32 last_full_charge_cap;
+	__le32 technology;
+	__le32 design_voltage;
+	__le32 design_cap_warn;
+	__le32 design_cap_low;
+	__le32 cycle_count;
+	__le32 measurement_accuracy;
+	__le32 max_sampling_time;
+	__le32 min_sampling_time;
+	__le32 max_avg_interval;
+	__le32 min_avg_interval;
+	__le32 bat_cap_granularity_1;
+	__le32 bat_cap_granularity_2;
+	__u8 model[21];
+	__u8 serial[11];
+	__u8 type[5];
+	__u8 oem_info[21];
+} __packed;
+
+static_assert(sizeof(struct spwr_bix) == 119);
+
+/* Equivalent to data returned in ACPI _BST method. */
+struct spwr_bst {
+	__le32 state;
+	__le32 present_rate;
+	__le32 remaining_cap;
+	__le32 present_voltage;
+} __packed;
+
+static_assert(sizeof(struct spwr_bst) == 16);
+
+#define SPWR_BIX_REVISION		0
+#define SPWR_BATTERY_VALUE_UNKNOWN	0xffffffff
+
+/* Get battery status (_STA) */
+SSAM_DEFINE_SYNC_REQUEST_CL_R(ssam_bat_get_sta, __le32, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x01,
+});
+
+/* Get battery static information (_BIX). */
+SSAM_DEFINE_SYNC_REQUEST_CL_R(ssam_bat_get_bix, struct spwr_bix, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x02,
+});
+
+/* Get battery dynamic information (_BST). */
+SSAM_DEFINE_SYNC_REQUEST_CL_R(ssam_bat_get_bst, struct spwr_bst, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x03,
+});
+
+/* Set battery trip point (_BTP). */
+SSAM_DEFINE_SYNC_REQUEST_CL_W(ssam_bat_set_btp, __le32, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x04,
+});
+
+
+/* -- Device structures. ---------------------------------------------------- */
+
+struct spwr_psy_properties {
+	const char *name;
+	struct ssam_event_registry registry;
+};
+
+struct spwr_battery_device {
+	struct ssam_device *sdev;
+
+	char name[32];
+	struct power_supply *psy;
+	struct power_supply_desc psy_desc;
+
+	struct delayed_work update_work;
+
+	struct ssam_event_notifier notif;
+
+	struct mutex lock;  /* Guards access to state data below. */
+	unsigned long timestamp;
+
+	__le32 sta;
+	struct spwr_bix bix;
+	struct spwr_bst bst;
+	u32 alarm;
+};
+
+
+/* -- Module parameters. ---------------------------------------------------- */
+
+static unsigned int cache_time = 1000;
+module_param(cache_time, uint, 0644);
+MODULE_PARM_DESC(cache_time, "battery state caching time in milliseconds [default: 1000]");
+
+
+/* -- State management. ----------------------------------------------------- */
+
+/*
+ * Delay for battery update quirk. See spwr_battery_recheck_adapter() below
+ * for more details.
+ */
+#define SPWR_AC_BAT_UPDATE_DELAY	msecs_to_jiffies(5000)
+
+static bool spwr_battery_present(struct spwr_battery_device *bat)
+{
+	lockdep_assert_held(&bat->lock);
+
+	return le32_to_cpu(bat->sta) & SAM_BATTERY_STA_PRESENT;
+}
+
+static int spwr_battery_load_sta(struct spwr_battery_device *bat)
+{
+	lockdep_assert_held(&bat->lock);
+
+	return ssam_retry(ssam_bat_get_sta, bat->sdev, &bat->sta);
+}
+
+static int spwr_battery_load_bix(struct spwr_battery_device *bat)
+{
+	int status;
+
+	lockdep_assert_held(&bat->lock);
+
+	if (!spwr_battery_present(bat))
+		return 0;
+
+	status = ssam_retry(ssam_bat_get_bix, bat->sdev, &bat->bix);
+
+	/* Enforce NULL terminated strings in case anything goes wrong... */
+	bat->bix.model[ARRAY_SIZE(bat->bix.model) - 1] = 0;
+	bat->bix.serial[ARRAY_SIZE(bat->bix.serial) - 1] = 0;
+	bat->bix.type[ARRAY_SIZE(bat->bix.type) - 1] = 0;
+	bat->bix.oem_info[ARRAY_SIZE(bat->bix.oem_info) - 1] = 0;
+
+	return status;
+}
+
+static int spwr_battery_load_bst(struct spwr_battery_device *bat)
+{
+	lockdep_assert_held(&bat->lock);
+
+	if (!spwr_battery_present(bat))
+		return 0;
+
+	return ssam_retry(ssam_bat_get_bst, bat->sdev, &bat->bst);
+}
+
+static int spwr_battery_set_alarm_unlocked(struct spwr_battery_device *bat, u32 value)
+{
+	__le32 value_le = cpu_to_le32(value);
+
+	lockdep_assert_held(&bat->lock);
+
+	bat->alarm = value;
+	return ssam_retry(ssam_bat_set_btp, bat->sdev, &value_le);
+}
+
+static int spwr_battery_update_bst_unlocked(struct spwr_battery_device *bat, bool cached)
+{
+	unsigned long cache_deadline = bat->timestamp + msecs_to_jiffies(cache_time);
+	int status;
+
+	lockdep_assert_held(&bat->lock);
+
+	if (cached && bat->timestamp && time_is_after_jiffies(cache_deadline))
+		return 0;
+
+	status = spwr_battery_load_sta(bat);
+	if (status)
+		return status;
+
+	status = spwr_battery_load_bst(bat);
+	if (status)
+		return status;
+
+	bat->timestamp = jiffies;
+	return 0;
+}
+
+static int spwr_battery_update_bst(struct spwr_battery_device *bat, bool cached)
+{
+	int status;
+
+	mutex_lock(&bat->lock);
+	status = spwr_battery_update_bst_unlocked(bat, cached);
+	mutex_unlock(&bat->lock);
+
+	return status;
+}
+
+static int spwr_battery_update_bix_unlocked(struct spwr_battery_device *bat)
+{
+	int status;
+
+	lockdep_assert_held(&bat->lock);
+
+	status = spwr_battery_load_sta(bat);
+	if (status)
+		return status;
+
+	status = spwr_battery_load_bix(bat);
+	if (status)
+		return status;
+
+	status = spwr_battery_load_bst(bat);
+	if (status)
+		return status;
+
+	if (bat->bix.revision != SPWR_BIX_REVISION)
+		dev_warn(&bat->sdev->dev, "unsupported battery revision: %u\n", bat->bix.revision);
+
+	bat->timestamp = jiffies;
+	return 0;
+}
+
+static u32 sprw_battery_get_full_cap_safe(struct spwr_battery_device *bat)
+{
+	u32 full_cap = get_unaligned_le32(&bat->bix.last_full_charge_cap);
+
+	lockdep_assert_held(&bat->lock);
+
+	if (full_cap == 0 || full_cap == SPWR_BATTERY_VALUE_UNKNOWN)
+		full_cap = get_unaligned_le32(&bat->bix.design_cap);
+
+	return full_cap;
+}
+
+static bool spwr_battery_is_full(struct spwr_battery_device *bat)
+{
+	u32 state = get_unaligned_le32(&bat->bst.state);
+	u32 full_cap = sprw_battery_get_full_cap_safe(bat);
+	u32 remaining_cap = get_unaligned_le32(&bat->bst.remaining_cap);
+
+	lockdep_assert_held(&bat->lock);
+
+	return full_cap != SPWR_BATTERY_VALUE_UNKNOWN && full_cap != 0 &&
+		remaining_cap != SPWR_BATTERY_VALUE_UNKNOWN &&
+		remaining_cap >= full_cap &&
+		state == 0;
+}
+
+static int spwr_battery_recheck_full(struct spwr_battery_device *bat)
+{
+	bool present;
+	u32 unit;
+	int status;
+
+	mutex_lock(&bat->lock);
+	unit = get_unaligned_le32(&bat->bix.power_unit);
+	present = spwr_battery_present(bat);
+
+	status = spwr_battery_update_bix_unlocked(bat);
+	if (status)
+		goto out;
+
+	/* If battery has been attached, (re-)initialize alarm. */
+	if (!present && spwr_battery_present(bat)) {
+		u32 cap_warn = get_unaligned_le32(&bat->bix.design_cap_warn);
+
+		status = spwr_battery_set_alarm_unlocked(bat, cap_warn);
+		if (status)
+			goto out;
+	}
+
+	/*
+	 * Warn if the unit has changed. This is something we genuinely don't
+	 * expect to happen, so make this a big warning. If it does, we'll
+	 * need to add support for it.
+	 */
+	WARN_ON(unit != get_unaligned_le32(&bat->bix.power_unit));
+
+out:
+	mutex_unlock(&bat->lock);
+
+	if (!status)
+		power_supply_changed(bat->psy);
+
+	return status;
+}
+
+static int spwr_battery_recheck_status(struct spwr_battery_device *bat)
+{
+	int status;
+
+	status = spwr_battery_update_bst(bat, false);
+	if (!status)
+		power_supply_changed(bat->psy);
+
+	return status;
+}
+
+static int spwr_battery_recheck_adapter(struct spwr_battery_device *bat)
+{
+	/*
+	 * Handle battery update quirk: When the battery is fully charged (or
+	 * charged up to the limit imposed by the UEFI battery limit) and the
+	 * adapter is plugged in or removed, the EC does not send a separate
+	 * event for the state (charging/discharging) change. Furthermore it
+	 * may take some time until the state is updated on the battery.
+	 * Schedule an update to solve this.
+	 */
+
+	schedule_delayed_work(&bat->update_work, SPWR_AC_BAT_UPDATE_DELAY);
+	return 0;
+}
+
+static u32 spwr_notify_bat(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct spwr_battery_device *bat = container_of(nf, struct spwr_battery_device, notif);
+	int status;
+
+	dev_dbg(&bat->sdev->dev, "power event (cid = %#04x, iid = %#04x, tid = %#04x)\n",
+		event->command_id, event->instance_id, event->target_id);
+
+	/* Handled here, needs to be handled for all targets/instances. */
+	if (event->command_id == SAM_EVENT_CID_BAT_ADP) {
+		status = spwr_battery_recheck_adapter(bat);
+		return ssam_notifier_from_errno(status) | SSAM_NOTIF_HANDLED;
+	}
+
+	if (bat->sdev->uid.target != event->target_id)
+		return 0;
+
+	if (bat->sdev->uid.instance != event->instance_id)
+		return 0;
+
+	switch (event->command_id) {
+	case SAM_EVENT_CID_BAT_BIX:
+		status = spwr_battery_recheck_full(bat);
+		break;
+
+	case SAM_EVENT_CID_BAT_BST:
+		status = spwr_battery_recheck_status(bat);
+		break;
+
+	case SAM_EVENT_CID_BAT_PROT:
+		/*
+		 * TODO: Implement support for battery protection status change
+		 *       event.
+		 */
+		status = 0;
+		break;
+
+	case SAM_EVENT_CID_BAT_DPTF:
+		/*
+		 * TODO: Implement support for DPTF event.
+		 */
+		status = 0;
+		break;
+
+	default:
+		return 0;
+	}
+
+	return ssam_notifier_from_errno(status) | SSAM_NOTIF_HANDLED;
+}
+
+static void spwr_battery_update_bst_workfn(struct work_struct *work)
+{
+	struct delayed_work *dwork = to_delayed_work(work);
+	struct spwr_battery_device *bat;
+	int status;
+
+	bat = container_of(dwork, struct spwr_battery_device, update_work);
+
+	status = spwr_battery_update_bst(bat, false);
+	if (!status)
+		power_supply_changed(bat->psy);
+
+	if (status)
+		dev_err(&bat->sdev->dev, "failed to update battery state: %d\n", status);
+}
+
+
+/* -- Properties. ----------------------------------------------------------- */
+
+static enum power_supply_property spwr_battery_props_chg[] = {
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+	POWER_SUPPLY_PROP_CYCLE_COUNT,
+	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
+	POWER_SUPPLY_PROP_CHARGE_FULL,
+	POWER_SUPPLY_PROP_CHARGE_NOW,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CAPACITY_LEVEL,
+	POWER_SUPPLY_PROP_MODEL_NAME,
+	POWER_SUPPLY_PROP_MANUFACTURER,
+	POWER_SUPPLY_PROP_SERIAL_NUMBER,
+};
+
+static enum power_supply_property spwr_battery_props_eng[] = {
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+	POWER_SUPPLY_PROP_CYCLE_COUNT,
+	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_POWER_NOW,
+	POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN,
+	POWER_SUPPLY_PROP_ENERGY_FULL,
+	POWER_SUPPLY_PROP_ENERGY_NOW,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CAPACITY_LEVEL,
+	POWER_SUPPLY_PROP_MODEL_NAME,
+	POWER_SUPPLY_PROP_MANUFACTURER,
+	POWER_SUPPLY_PROP_SERIAL_NUMBER,
+};
+
+static int spwr_battery_prop_status(struct spwr_battery_device *bat)
+{
+	u32 state = get_unaligned_le32(&bat->bst.state);
+	u32 present_rate = get_unaligned_le32(&bat->bst.present_rate);
+
+	lockdep_assert_held(&bat->lock);
+
+	if (state & SAM_BATTERY_STATE_DISCHARGING)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+
+	if (state & SAM_BATTERY_STATE_CHARGING)
+		return POWER_SUPPLY_STATUS_CHARGING;
+
+	if (spwr_battery_is_full(bat))
+		return POWER_SUPPLY_STATUS_FULL;
+
+	if (present_rate == 0)
+		return POWER_SUPPLY_STATUS_NOT_CHARGING;
+
+	return POWER_SUPPLY_STATUS_UNKNOWN;
+}
+
+static int spwr_battery_prop_technology(struct spwr_battery_device *bat)
+{
+	lockdep_assert_held(&bat->lock);
+
+	if (!strcasecmp("NiCd", bat->bix.type))
+		return POWER_SUPPLY_TECHNOLOGY_NiCd;
+
+	if (!strcasecmp("NiMH", bat->bix.type))
+		return POWER_SUPPLY_TECHNOLOGY_NiMH;
+
+	if (!strcasecmp("LION", bat->bix.type))
+		return POWER_SUPPLY_TECHNOLOGY_LION;
+
+	if (!strncasecmp("LI-ION", bat->bix.type, 6))
+		return POWER_SUPPLY_TECHNOLOGY_LION;
+
+	if (!strcasecmp("LiP", bat->bix.type))
+		return POWER_SUPPLY_TECHNOLOGY_LIPO;
+
+	return POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
+}
+
+static int spwr_battery_prop_capacity(struct spwr_battery_device *bat)
+{
+	u32 full_cap = sprw_battery_get_full_cap_safe(bat);
+	u32 remaining_cap = get_unaligned_le32(&bat->bst.remaining_cap);
+
+	lockdep_assert_held(&bat->lock);
+
+	if (full_cap == 0 || full_cap == SPWR_BATTERY_VALUE_UNKNOWN)
+		return -ENODEV;
+
+	if (remaining_cap == SPWR_BATTERY_VALUE_UNKNOWN)
+		return -ENODEV;
+
+	return remaining_cap * 100 / full_cap;
+}
+
+static int spwr_battery_prop_capacity_level(struct spwr_battery_device *bat)
+{
+	u32 state = get_unaligned_le32(&bat->bst.state);
+	u32 remaining_cap = get_unaligned_le32(&bat->bst.remaining_cap);
+
+	lockdep_assert_held(&bat->lock);
+
+	if (state & SAM_BATTERY_STATE_CRITICAL)
+		return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
+
+	if (spwr_battery_is_full(bat))
+		return POWER_SUPPLY_CAPACITY_LEVEL_FULL;
+
+	if (remaining_cap <= bat->alarm)
+		return POWER_SUPPLY_CAPACITY_LEVEL_LOW;
+
+	return POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
+}
+
+static int spwr_battery_get_property(struct power_supply *psy, enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct spwr_battery_device *bat = power_supply_get_drvdata(psy);
+	u32 value;
+	int status;
+
+	mutex_lock(&bat->lock);
+
+	status = spwr_battery_update_bst_unlocked(bat, true);
+	if (status)
+		goto out;
+
+	/* Abort if battery is not present. */
+	if (!spwr_battery_present(bat) && psp != POWER_SUPPLY_PROP_PRESENT) {
+		status = -ENODEV;
+		goto out;
+	}
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_STATUS:
+		val->intval = spwr_battery_prop_status(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = spwr_battery_present(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		val->intval = spwr_battery_prop_technology(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_CYCLE_COUNT:
+		value = get_unaligned_le32(&bat->bix.cycle_count);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
+		value = get_unaligned_le32(&bat->bix.design_voltage);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		value = get_unaligned_le32(&bat->bst.present_voltage);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+	case POWER_SUPPLY_PROP_POWER_NOW:
+		value = get_unaligned_le32(&bat->bst.present_rate);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
+		value = get_unaligned_le32(&bat->bix.design_cap);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+	case POWER_SUPPLY_PROP_ENERGY_FULL:
+		value = get_unaligned_le32(&bat->bix.last_full_charge_cap);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_CHARGE_NOW:
+	case POWER_SUPPLY_PROP_ENERGY_NOW:
+		value = get_unaligned_le32(&bat->bst.remaining_cap);
+		if (value != SPWR_BATTERY_VALUE_UNKNOWN)
+			val->intval = value * 1000;
+		else
+			status = -ENODEV;
+		break;
+
+	case POWER_SUPPLY_PROP_CAPACITY:
+		val->intval = spwr_battery_prop_capacity(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
+		val->intval = spwr_battery_prop_capacity_level(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_MODEL_NAME:
+		val->strval = bat->bix.model;
+		break;
+
+	case POWER_SUPPLY_PROP_MANUFACTURER:
+		val->strval = bat->bix.oem_info;
+		break;
+
+	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
+		val->strval = bat->bix.serial;
+		break;
+
+	default:
+		status = -EINVAL;
+		break;
+	}
+
+out:
+	mutex_unlock(&bat->lock);
+	return status;
+}
+
+
+/* -- Alarm attribute. ------------------------------------------------------ */
+
+static ssize_t spwr_battery_alarm_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct power_supply *psy = dev_get_drvdata(dev);
+	struct spwr_battery_device *bat = power_supply_get_drvdata(psy);
+	int status;
+
+	mutex_lock(&bat->lock);
+	status = sysfs_emit(buf, "%d\n", bat->alarm * 1000);
+	mutex_unlock(&bat->lock);
+
+	return status;
+}
+
+static ssize_t spwr_battery_alarm_store(struct device *dev, struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct power_supply *psy = dev_get_drvdata(dev);
+	struct spwr_battery_device *bat = power_supply_get_drvdata(psy);
+	unsigned long value;
+	int status;
+
+	status = kstrtoul(buf, 0, &value);
+	if (status)
+		return status;
+
+	mutex_lock(&bat->lock);
+
+	if (!spwr_battery_present(bat)) {
+		mutex_unlock(&bat->lock);
+		return -ENODEV;
+	}
+
+	status = spwr_battery_set_alarm_unlocked(bat, value / 1000);
+	if (status) {
+		mutex_unlock(&bat->lock);
+		return status;
+	}
+
+	mutex_unlock(&bat->lock);
+	return count;
+}
+
+static const struct device_attribute alarm_attr = {
+	.attr = {.name = "alarm", .mode = 0644},
+	.show = spwr_battery_alarm_show,
+	.store = spwr_battery_alarm_store,
+};
+
+
+/* -- Device setup. --------------------------------------------------------- */
+
+static void spwr_battery_init(struct spwr_battery_device *bat, struct ssam_device *sdev,
+			      struct ssam_event_registry registry, const char *name)
+{
+	mutex_init(&bat->lock);
+	strncpy(bat->name, name, ARRAY_SIZE(bat->name) - 1);
+
+	bat->sdev = sdev;
+
+	bat->notif.base.priority = 1;
+	bat->notif.base.fn = spwr_notify_bat;
+	bat->notif.event.reg = registry;
+	bat->notif.event.id.target_category = sdev->uid.category;
+	bat->notif.event.id.instance = 0;
+	bat->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	bat->notif.event.flags = SSAM_EVENT_SEQUENCED;
+
+	bat->psy_desc.name = bat->name;
+	bat->psy_desc.type = POWER_SUPPLY_TYPE_BATTERY;
+	bat->psy_desc.get_property = spwr_battery_get_property;
+
+	INIT_DELAYED_WORK(&bat->update_work, spwr_battery_update_bst_workfn);
+}
+
+static void spwr_battery_destroy(struct spwr_battery_device *bat)
+{
+	mutex_destroy(&bat->lock);
+}
+
+static int spwr_battery_register(struct spwr_battery_device *bat)
+{
+	struct power_supply_config psy_cfg = {};
+	__le32 sta;
+	int status;
+
+	/* Make sure the device is there and functioning properly. */
+	status = ssam_retry(ssam_bat_get_sta, bat->sdev, &sta);
+	if (status)
+		return status;
+
+	if ((le32_to_cpu(sta) & SAM_BATTERY_STA_OK) != SAM_BATTERY_STA_OK)
+		return -ENODEV;
+
+	/* Satisfy lockdep although we are in an exclusive context here. */
+	mutex_lock(&bat->lock);
+
+	status = spwr_battery_update_bix_unlocked(bat);
+	if (status) {
+		mutex_unlock(&bat->lock);
+		return status;
+	}
+
+	if (spwr_battery_present(bat)) {
+		u32 cap_warn = get_unaligned_le32(&bat->bix.design_cap_warn);
+
+		status = spwr_battery_set_alarm_unlocked(bat, cap_warn);
+		if (status) {
+			mutex_unlock(&bat->lock);
+			return status;
+		}
+	}
+
+	mutex_unlock(&bat->lock);
+
+	switch (get_unaligned_le32(&bat->bix.power_unit)) {
+	case SAM_BATTERY_POWER_UNIT_mW:
+		bat->psy_desc.properties = spwr_battery_props_eng;
+		bat->psy_desc.num_properties = ARRAY_SIZE(spwr_battery_props_eng);
+		break;
+
+	case SAM_BATTERY_POWER_UNIT_mA:
+		bat->psy_desc.properties = spwr_battery_props_chg;
+		bat->psy_desc.num_properties = ARRAY_SIZE(spwr_battery_props_chg);
+		break;
+
+	default:
+		dev_err(&bat->sdev->dev, "unsupported battery power unit: %u\n",
+			get_unaligned_le32(&bat->bix.power_unit));
+		return -EINVAL;
+	}
+
+	psy_cfg.drv_data = bat;
+	bat->psy = power_supply_register(&bat->sdev->dev, &bat->psy_desc, &psy_cfg);
+	if (IS_ERR(bat->psy))
+		return PTR_ERR(bat->psy);
+
+	status = ssam_notifier_register(bat->sdev->ctrl, &bat->notif);
+	if (status)
+		goto err_notif;
+
+	status = device_create_file(&bat->psy->dev, &alarm_attr);
+	if (status)
+		goto err_file;
+
+	return 0;
+
+err_file:
+	ssam_notifier_unregister(bat->sdev->ctrl, &bat->notif);
+err_notif:
+	power_supply_unregister(bat->psy);
+	return status;
+}
+
+static void spwr_battery_unregister(struct spwr_battery_device *bat)
+{
+	ssam_notifier_unregister(bat->sdev->ctrl, &bat->notif);
+	cancel_delayed_work_sync(&bat->update_work);
+	device_remove_file(&bat->psy->dev, &alarm_attr);
+	power_supply_unregister(bat->psy);
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int __maybe_unused surface_battery_resume(struct device *dev)
+{
+	return spwr_battery_recheck_full(dev_get_drvdata(dev));
+}
+SIMPLE_DEV_PM_OPS(surface_battery_pm_ops, NULL, surface_battery_resume);
+
+static int surface_battery_probe(struct ssam_device *sdev)
+{
+	const struct spwr_psy_properties *p;
+	struct spwr_battery_device *bat;
+	int status;
+
+	p = ssam_device_get_match_data(sdev);
+	if (!p)
+		return -ENODEV;
+
+	bat = devm_kzalloc(&sdev->dev, sizeof(*bat), GFP_KERNEL);
+	if (!bat)
+		return -ENOMEM;
+
+	spwr_battery_init(bat, sdev, p->registry, p->name);
+	ssam_device_set_drvdata(sdev, bat);
+
+	status = spwr_battery_register(bat);
+	if (status)
+		spwr_battery_destroy(bat);
+
+	return status;
+}
+
+static void surface_battery_remove(struct ssam_device *sdev)
+{
+	struct spwr_battery_device *bat = ssam_device_get_drvdata(sdev);
+
+	spwr_battery_unregister(bat);
+	spwr_battery_destroy(bat);
+}
+
+static const struct spwr_psy_properties spwr_psy_props_bat1 = {
+	.name = "BAT1",
+	.registry = SSAM_EVENT_REGISTRY_SAM,
+};
+
+static const struct spwr_psy_properties spwr_psy_props_bat2_sb3 = {
+	.name = "BAT2",
+	.registry = SSAM_EVENT_REGISTRY_KIP,
+};
+
+static const struct ssam_device_id surface_battery_match[] = {
+	{ SSAM_SDEV(BAT, 0x01, 0x01, 0x00), (unsigned long)&spwr_psy_props_bat1     },
+	{ SSAM_SDEV(BAT, 0x02, 0x01, 0x00), (unsigned long)&spwr_psy_props_bat2_sb3 },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_battery_match);
+
+static struct ssam_device_driver surface_battery_driver = {
+	.probe = surface_battery_probe,
+	.remove = surface_battery_remove,
+	.match_table = surface_battery_match,
+	.driver = {
+		.name = "surface_battery",
+		.pm = &surface_battery_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_ssam_device_driver(surface_battery_driver);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("Battery driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
