[2/2] platform/x86: x86-android-tablets: Add Vexia EDU ATLA 10 EC battery driver

diff --git a/drivers/platform/x86/x86-android-tablets/Makefile b/drivers/platform/x86/x86-android-tablets/Makefile
index 41ece5a37137..bc505ffcd2bf 100644
--- a/drivers/platform/x86/x86-android-tablets/Makefile
+++ b/drivers/platform/x86/x86-android-tablets/Makefile
@@ -4,6 +4,7 @@ 
 #
 
 obj-$(CONFIG_X86_ANDROID_TABLETS) += x86-android-tablets.o
+obj-$(CONFIG_X86_ANDROID_TABLETS) += vexia_atla10_ec.o
 
 x86-android-tablets-y := core.o dmi.o shared-psy-info.o \
 			 asus.o lenovo.o other.o
diff --git a/drivers/platform/x86/x86-android-tablets/vexia_atla10_ec.c b/drivers/platform/x86/x86-android-tablets/vexia_atla10_ec.c
new file mode 100644
index 000000000000..c5e6656d24fc
--- /dev/null
+++ b/drivers/platform/x86/x86-android-tablets/vexia_atla10_ec.c
@@ -0,0 +1,264 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * power_supply class (battery) driver for the I2C attached embedded controller
+ * found on Vexia EDU ATLA 10 (9V version) tablets.
+ *
+ * This is based on the ACPI Battery device in the DSDT which should work
+ * expect that it expects the I2C controller to be enumerated as an ACPI
+ * device and the tablet's BIOS enumerates all LPSS devices as PCI devices
+ * (and changing the LPSS BIOS settings from PCI -> ACPI does not work).
+ *
+ * Copyright (c) 2024 Hans de Goede <hansg@kernel.org>
+ */
+
+#include <linux/bits.h>
+#include <linux/devm-helpers.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/power_supply.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include <asm/byteorder.h>
+
+/* State field uses ACPI Battery spec status bits */
+#define ACPI_BATTERY_STATE_DISCHARGING		BIT(0)
+#define ACPI_BATTERY_STATE_CHARGING		BIT(1)
+
+#define ATLA10_EC_BATTERY_STATE_COMMAND		0x87
+#define ATLA10_EC_BATTERY_INFO_COMMAND		0x88
+
+/* From broken ACPI battery device in DSDT */
+#define ATLA10_EC_VOLTAGE_MIN_DESIGN		3750000
+
+struct atla10_ec_battery_state {
+	u8 len;				/* Struct length excluding the len field, always 12 */
+	u8 status;			/* Using ACPI Battery spec status bits */
+	u8 capacity;			/* Percent */
+	__le16 charge_now;		/* mAh */
+	__le16 voltage_now;		/* mV */
+	__le16 current_now;		/* mA */
+	__le16 charge_full;		/* mAh */
+	__le16 temp;			/* centi degrees celcius */
+} __packed;
+
+struct atla10_ec_battery_info {
+	u8 len;				/* Struct length excluding the len field, always 6 */
+	__le16 charge_full_design;	/* mAh */
+	__le16 voltage_now;		/* mV, should be design voltage, but is not ? */
+	__le16 charge_full_design2;	/* mAh */
+} __packed;
+
+struct atla10_ec_data {
+	struct i2c_client *client;
+	struct power_supply *psy;
+	struct delayed_work work;
+	struct mutex update_lock;
+	struct atla10_ec_battery_info info;
+	struct atla10_ec_battery_state state;
+	bool valid;			/* true if state is valid */
+	unsigned long last_update;	/* In jiffies */
+};
+
+static int atla10_ec_cmd(struct atla10_ec_data *data, u8 cmd, u8 len, u8 *values)
+{
+	struct device *dev = &data->client->dev;
+	int ret;
+
+	ret = i2c_smbus_read_i2c_block_data(data->client, cmd, len, values);
+	if (ret != len) {
+		dev_err(dev, "I2C command 0x%02x error: %d\n", cmd, ret);
+		return -EIO;
+	}
+
+	if (values[0] != (len - 1)) {
+		dev_err(dev, "I2C command 0x%02x header length mismatch expected %u got %u\n",
+			cmd, len - 1, values[0]);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int atla10_ec_update(struct atla10_ec_data *data)
+{
+	int ret;
+
+	/* Cache data for 5 seconds */
+	if (data->valid && time_before(jiffies, data->last_update + 5 * HZ))
+		return 0;
+
+	ret = atla10_ec_cmd(data, ATLA10_EC_BATTERY_STATE_COMMAND,
+			    sizeof(data->state), (u8 *)&data->state);
+	if (ret)
+		return ret;
+
+	data->last_update = jiffies;
+	data->valid = true;
+	return 0;
+}
+
+static int atla10_ec_psy_get_property(struct power_supply *psy,
+				      enum power_supply_property psp,
+				      union power_supply_propval *val)
+{
+	struct atla10_ec_data *data = power_supply_get_drvdata(psy);
+	int charge_now, charge_full, ret;
+
+	guard(mutex)(&data->update_lock);
+
+	ret = atla10_ec_update(data);
+	if (ret)
+		return ret;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_STATUS:
+		if (data->state.status & ACPI_BATTERY_STATE_DISCHARGING)
+			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		else if (data->state.status & ACPI_BATTERY_STATE_CHARGING)
+			val->intval = POWER_SUPPLY_STATUS_CHARGING;
+		else if (data->state.capacity == 100)
+			val->intval = POWER_SUPPLY_STATUS_FULL;
+		else
+			val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
+		break;
+	case POWER_SUPPLY_PROP_CAPACITY:
+		val->intval = data->state.capacity;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_NOW:
+		/*
+		 * The EC has a bug where it reports charge-full-design as
+		 * charge-now when the battery is full. Clamp charge-now to
+		 * charge-full to workaround this.
+		 */
+		charge_now = le16_to_cpu(data->state.charge_now);
+		charge_full = le16_to_cpu(data->state.charge_full);
+		val->intval = min(charge_now, charge_full) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		val->intval = le16_to_cpu(data->state.voltage_now) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		val->intval = le16_to_cpu(data->state.current_now) * 1000;
+		/*
+		 * Documentation/ABI/testing/sysfs-class-power specifies
+		 * negative current for discharing.
+		 */
+		if (data->state.status & ACPI_BATTERY_STATE_DISCHARGING)
+			val->intval = -val->intval;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		val->intval = le16_to_cpu(data->state.charge_full) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_TEMP:
+		val->intval = le16_to_cpu(data->state.temp) / 10;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+		val->intval = le16_to_cpu(data->info.charge_full_design) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
+		val->intval = ATLA10_EC_VOLTAGE_MIN_DESIGN;
+		break;
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = 1;
+		break;
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		val->intval = POWER_SUPPLY_TECHNOLOGY_LIPO;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void atla10_ec_external_power_changed_work(struct work_struct *work)
+{
+	struct atla10_ec_data *data = container_of(work, struct atla10_ec_data, work.work);
+
+	dev_dbg(&data->client->dev, "External power changed\n");
+	data->valid = false;
+	power_supply_changed(data->psy);
+}
+
+static void atla10_ec_external_power_changed(struct power_supply *psy)
+{
+	struct atla10_ec_data *data = power_supply_get_drvdata(psy);
+
+	/* After charger plug in/out wait 0.5s for things to stabilize */
+	mod_delayed_work(system_wq, &data->work, HZ / 2);
+}
+
+static const enum power_supply_property atla10_ec_psy_props[] = {
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CHARGE_NOW,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CHARGE_FULL,
+	POWER_SUPPLY_PROP_TEMP,
+	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+};
+
+static const struct power_supply_desc atla10_ec_psy_desc = {
+	.name = "atla10_ec_battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = atla10_ec_psy_props,
+	.num_properties = ARRAY_SIZE(atla10_ec_psy_props),
+	.get_property = atla10_ec_psy_get_property,
+	.external_power_changed = atla10_ec_external_power_changed,
+};
+
+static int atla10_ec_probe(struct i2c_client *client)
+{
+	struct power_supply_config psy_cfg = { };
+	struct device *dev = &client->dev;
+	struct atla10_ec_data *data;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	psy_cfg.drv_data = data;
+	data->client = client;
+
+	ret = devm_mutex_init(dev, &data->update_lock);
+	if (ret)
+		return ret;
+
+	ret = devm_delayed_work_autocancel(dev, &data->work,
+					   atla10_ec_external_power_changed_work);
+	if (ret)
+		return ret;
+
+	ret = atla10_ec_cmd(data, ATLA10_EC_BATTERY_INFO_COMMAND,
+			    sizeof(data->info), (u8 *)&data->info);
+	if (ret)
+		return ret;
+
+	data->psy = devm_power_supply_register(dev, &atla10_ec_psy_desc, &psy_cfg);
+	return PTR_ERR_OR_ZERO(data->psy);
+}
+
+static const struct i2c_device_id atla10_ec_id_table[] = {
+	{ "vexia_atla10_ec" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, atla10_ec_id_table);
+
+static struct i2c_driver atla10_ec_driver = {
+	.driver = {
+		.name = "vexia_atla10_ec",
+	},
+	.probe = atla10_ec_probe,
+	.id_table = atla10_ec_id_table,
+};
+module_i2c_driver(atla10_ec_driver);
+
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_DESCRIPTION("Battery driver for Vexia EDU ATLA 10 tablet EC");
+MODULE_LICENSE("GPL");