[PATCH v2 4/6] power: supply: Add battery gauge driver for Acer Iconia Tab A500

[Dmitry Osipenko]

This patch adds battery gauge driver for Acer Iconia Tab A500 device.
The battery gauge function is provided via the Embedded Controller,
which is found on the Acer A500.

Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
 drivers/power/supply/Kconfig             |   6 +
 drivers/power/supply/Makefile            |   1 +
 drivers/power/supply/acer_a500_battery.c | 297 +++++++++++++++++++++++
 3 files changed, 304 insertions(+)
 create mode 100644 drivers/power/supply/acer_a500_battery.c

diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index d1ccf17df42e..3daf0e359964 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -752,4 +752,10 @@ config CHARGER_WILCO
 	  information can be found in
 	  Documentation/ABI/testing/sysfs-class-power-wilco
 
+config BATTERY_ACER_A500
+	tristate "Acer Iconia Tab A500 battery driver"
+	depends on MFD_ACER_A500_EC
+	help
+	  Say Y to include support for Acer Iconia Tab A500 battery fuel gauge.
+
 endif # POWER_SUPPLY
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index b3c694a65114..08a5b49e2936 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -96,3 +96,4 @@ obj-$(CONFIG_CHARGER_UCS1002)	+= ucs1002_power.o
 obj-$(CONFIG_CHARGER_BD70528)	+= bd70528-charger.o
 obj-$(CONFIG_CHARGER_BD99954)	+= bd99954-charger.o
 obj-$(CONFIG_CHARGER_WILCO)	+= wilco-charger.o
+obj-$(CONFIG_BATTERY_ACER_A500)	+= acer_a500_battery.o
diff --git a/drivers/power/supply/acer_a500_battery.c b/drivers/power/supply/acer_a500_battery.c
new file mode 100644
index 000000000000..93135933c8af
--- /dev/null
+++ b/drivers/power/supply/acer_a500_battery.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Battery driver for Acer Iconia Tab A500.
+ *
+ * Copyright 2020 GRATE-driver project.
+ *
+ * Based on downstream driver from Acer Inc.
+ * Based on NVIDIA Gas Gauge driver for SBS Compliant Batteries.
+ *
+ * Copyright (c) 2010, NVIDIA Corporation.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/regmap.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+enum {
+	REG_CAPACITY,
+	REG_VOLTAGE,
+	REG_CURRENT,
+	REG_DESIGN_CAPACITY,
+	REG_TEMPERATURE,
+};
+
+#define EC_DATA(_reg, _psp) {			\
+	.psp = POWER_SUPPLY_PROP_ ## _psp,	\
+	.reg = _reg,				\
+}
+
+static const struct battery_register {
+	enum power_supply_property psp;
+	unsigned int reg;
+} ec_data[] = {
+	[REG_CAPACITY]		= EC_DATA(0x00, CAPACITY),
+	[REG_VOLTAGE]		= EC_DATA(0x01, VOLTAGE_NOW),
+	[REG_CURRENT]		= EC_DATA(0x03, CURRENT_NOW),
+	[REG_DESIGN_CAPACITY]	= EC_DATA(0x08, CHARGE_FULL_DESIGN),
+	[REG_TEMPERATURE]	= EC_DATA(0x0a, TEMP),
+};
+
+static const enum power_supply_property a500_battery_properties[] = {
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+	POWER_SUPPLY_PROP_TEMP,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+};
+
+struct a500_battery {
+	struct delayed_work poll_work;
+	struct power_supply *psy;
+	struct regmap *rmap;
+	unsigned int capacity;
+};
+
+static bool a500_battery_update_capacity(struct a500_battery *bat)
+{
+	unsigned int capacity;
+	int err;
+
+	err = regmap_read(bat->rmap, ec_data[REG_CAPACITY].reg, &capacity);
+	if (err)
+		return false;
+
+	/* capacity can be >100% even if max value is 100% */
+	capacity = min(capacity, 100u);
+
+	if (bat->capacity != capacity) {
+		bat->capacity = capacity;
+		return true;
+	}
+
+	return false;
+}
+
+static int a500_battery_get_status(struct a500_battery *bat)
+{
+	if (bat->capacity < 100) {
+		if (power_supply_am_i_supplied(bat->psy))
+			return POWER_SUPPLY_STATUS_CHARGING;
+		else
+			return POWER_SUPPLY_STATUS_DISCHARGING;
+	}
+
+	return POWER_SUPPLY_STATUS_FULL;
+}
+
+static void a500_battery_unit_adjustment(struct device *dev,
+					 enum power_supply_property psp,
+					 union power_supply_propval *val)
+{
+	const unsigned int base_unit_conversion = 1000;
+	const unsigned int temp_kelvin_to_celsius = 2731;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		val->intval *= base_unit_conversion;
+		break;
+
+	case POWER_SUPPLY_PROP_TEMP:
+		val->intval -= temp_kelvin_to_celsius;
+		break;
+
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = !!val->intval;
+		break;
+
+	default:
+		dev_dbg(dev,
+			"%s: no need for unit conversion %d\n", __func__, psp);
+	}
+}
+
+static int a500_battery_get_ec_data_index(struct device *dev,
+					  enum power_supply_property psp)
+{
+	unsigned int i;
+
+	/*
+	 * DESIGN_CAPACITY register always returns a non-zero value if
+	 * battery is connected and zero if disconnected, hence we'll use
+	 * it for judging the battery presence.
+	 */
+	if (psp == POWER_SUPPLY_PROP_PRESENT)
+		psp = POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN;
+
+	for (i = 0; i < ARRAY_SIZE(ec_data); i++)
+		if (psp == ec_data[i].psp)
+			return i;
+
+	dev_dbg(dev, "%s: invalid property %u\n", __func__, psp);
+
+	return -EINVAL;
+}
+
+static int a500_battery_get_property(struct power_supply *psy,
+				     enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct a500_battery *bat = power_supply_get_drvdata(psy);
+	struct device *dev = psy->dev.parent;
+	int ret = 0;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_STATUS:
+		val->intval = a500_battery_get_status(bat);
+		break;
+
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
+		break;
+
+	case POWER_SUPPLY_PROP_CAPACITY:
+		a500_battery_update_capacity(bat);
+		val->intval = bat->capacity;
+		break;
+
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+	case POWER_SUPPLY_PROP_PRESENT:
+	case POWER_SUPPLY_PROP_TEMP:
+		ret = a500_battery_get_ec_data_index(dev, psp);
+		if (ret < 0)
+			break;
+
+		ret = regmap_read(bat->rmap, ec_data[ret].reg, &val->intval);
+		break;
+
+	default:
+		dev_err(dev, "%s: invalid property %u\n", __func__, psp);
+		return -EINVAL;
+	}
+
+	if (!ret) {
+		/* convert units to match requirements of power supply class */
+		a500_battery_unit_adjustment(dev, psp, val);
+	}
+
+	dev_dbg(dev, "%s: property = %d, value = %x\n",
+		__func__, psp, val->intval);
+
+	/* return NODATA for properties if battery not presents */
+	if (ret)
+		return -ENODATA;
+
+	return 0;
+}
+
+static void a500_battery_poll_work(struct work_struct *work)
+{
+	struct a500_battery *bat;
+	bool capacity_changed;
+
+	bat = container_of(work, struct a500_battery, poll_work.work);
+	capacity_changed = a500_battery_update_capacity(bat);
+
+	if (capacity_changed)
+		power_supply_changed(bat->psy);
+
+	/* continuously send uevent notification */
+	schedule_delayed_work(&bat->poll_work, 30 * HZ);
+}
+
+static const struct power_supply_desc a500_battery_desc = {
+	.name = "ec-battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = a500_battery_properties,
+	.get_property = a500_battery_get_property,
+	.num_properties = ARRAY_SIZE(a500_battery_properties),
+	.external_power_changed = power_supply_changed,
+};
+
+static int a500_battery_probe(struct platform_device *pdev)
+{
+	struct power_supply_config psy_cfg = {};
+	struct a500_battery *bat;
+
+	bat = devm_kzalloc(&pdev->dev, sizeof(*bat), GFP_KERNEL);
+	if (!bat)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, bat);
+
+	psy_cfg.of_node = pdev->dev.parent->of_node;
+	psy_cfg.drv_data = bat;
+
+	bat->rmap = dev_get_regmap(pdev->dev.parent, "KB930");
+	if (!bat->rmap)
+		return -EINVAL;
+
+	bat->psy = devm_power_supply_register_no_ws(&pdev->dev,
+						    &a500_battery_desc,
+						    &psy_cfg);
+	if (IS_ERR(bat->psy))
+		return dev_err_probe(&pdev->dev, PTR_ERR(bat->psy),
+				     "failed to register battery\n");
+
+	INIT_DELAYED_WORK(&bat->poll_work, a500_battery_poll_work);
+	schedule_delayed_work(&bat->poll_work, HZ);
+
+	return 0;
+}
+
+static int a500_battery_remove(struct platform_device *pdev)
+{
+	struct a500_battery *bat = dev_get_drvdata(&pdev->dev);
+
+	cancel_delayed_work_sync(&bat->poll_work);
+
+	return 0;
+}
+
+static int __maybe_unused a500_battery_suspend(struct device *dev)
+{
+	struct a500_battery *bat = dev_get_drvdata(dev);
+
+	cancel_delayed_work_sync(&bat->poll_work);
+
+	return 0;
+}
+
+static int __maybe_unused a500_battery_resume(struct device *dev)
+{
+	struct a500_battery *bat = dev_get_drvdata(dev);
+
+	schedule_delayed_work(&bat->poll_work, HZ);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(a500_battery_pm_ops,
+			 a500_battery_suspend, a500_battery_resume);
+
+static struct platform_driver a500_battery_driver = {
+	.driver = {
+		.name = "acer-a500-iconia-battery",
+		.pm = &a500_battery_pm_ops,
+	},
+	.probe = a500_battery_probe,
+	.remove = a500_battery_remove,
+};
+module_platform_driver(a500_battery_driver);
+
+MODULE_DESCRIPTION("Battery gauge driver for Acer Iconia Tab A500");
+MODULE_AUTHOR("Dmitry Osipenko <digetx@xxxxxxxxx>");
+MODULE_ALIAS("platform:acer-a500-iconia-battery");
+MODULE_LICENSE("GPL");
-- 
2.27.0