ARM: tegra: Surface RT: battery support

Custom driver derived from original APCI SSDT table.
Works for APX and UEFI.
Use CONFIG_BATTERY_SURFACE_RT=y

Signed-off-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>

MAINTAINERS

@@ -12374,6 +12374,13 @@ L:	platform-driver-x86@vger.kernel.org
 S:	Supported
 F:	drivers/platform/surface/surfacepro3_button.c
 
+MICROSOFT SURFACE RT
+M:	Jonas Schwöbel <jonasschwoebel@yahoo.de>
+S:	Supported
+F:	drivers/power/supply/surface-rt-battery.c
+F:	arch/arm/boot/dts/tegra30-microsoft-surface-rt.dts
+F:	arch/arm/boot/dts/tegra30-microsoft-surface-rt-efi.dts
+
 MICROSOFT SURFACE SYSTEM AGGREGATOR SUBSYSTEM
 M:	Maximilian Luz <luzmaximilian@gmail.com>
 L:	platform-driver-x86@vger.kernel.org

arch/arm/boot/dts/tegra30-microsoft-surface-rt.dts

@@ -116,6 +116,12 @@
 		status = "okay";
 		clock-frequency = <400000>;
 
+		battery@a {
+			compatible = "microsoft,surface-rt-battery";
+			reg = <0x0a>;
+			powerdown-gpios = <&gpio TEGRA_GPIO(N, 3) GPIO_ACTIVE_LOW>;
+		};
+
 		pmic: tps65911@2d {
 			compatible = "ti,tps65911";
 			reg = <0x2d>;

drivers/power/supply/Kconfig

@@ -851,4 +851,11 @@ config CHARGER_SURFACE
 	  Microsoft Surface devices, i.e. Surface Pro 7, Surface Laptop 3,
 	  Surface Book 3, and Surface Laptop Go.
 
+config BATTERY_SURFACE_RT
+	tristate "Battery driver for 1st-generation Microsoft Surface RT"
+	depends on I2C && GPIOLIB
+	help
+	  UEFI/APX driver for Surface RT battery
+	  Say M or Y here to include battery driver
+
 endif # POWER_SUPPLY

drivers/power/supply/Makefile

@@ -105,3 +105,4 @@ obj-$(CONFIG_RN5T618_POWER)	+= rn5t618_power.o
 obj-$(CONFIG_BATTERY_ACER_A500)	+= acer_a500_battery.o
 obj-$(CONFIG_BATTERY_SURFACE)	+= surface_battery.o
 obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
+obj-$(CONFIG_BATTERY_SURFACE_RT)	+= surface-rt-battery.o

drivers/power/supply/surface-rt-battery.c

@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/power_supply.h>
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/types.h>
+#include <linux/gpio/consumer.h>
+#include <linux/delay.h>
+
+struct srt_battery_device {
+	struct i2c_client *client;
+	struct device *dev;
+	struct power_supply *battery;
+	struct gpio_desc *powerdown_gpio;
+};
+
+static enum power_supply_property srt_battery_power_supply_props[] = {
+	POWER_SUPPLY_PROP_MANUFACTURER,
+	POWER_SUPPLY_PROP_MODEL_NAME,
+	POWER_SUPPLY_PROP_SERIAL_NUMBER,
+
+	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
+	POWER_SUPPLY_PROP_CHARGE_FULL,
+	POWER_SUPPLY_PROP_CHARGE_NOW,
+
+	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CYCLE_COUNT,
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+};
+
+static int readString(struct i2c_client *client_adap, char *buf, u8 address, u8 size)
+{
+	struct i2c_msg msg[2];
+
+	msg[0].addr = client_adap->addr;
+	msg[0].flags = 0;
+	msg[0].buf = &address;
+	msg[0].len = 1;
+
+	msg[1].addr = client_adap->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].buf = buf;
+	msg[1].len = size;
+
+	return i2c_transfer(client_adap->adapter, msg, 2);
+}
+
+static int srt_battery_power_supply_get_property(struct power_supply *psy,
+											enum power_supply_property psp,
+											union power_supply_propval *val)
+{
+	struct srt_battery_device *srt_battery = power_supply_get_drvdata(psy);
+	struct i2c_client *client = srt_battery->client;
+
+	static char strBuf[8];
+
+	gpiod_set_value(srt_battery->powerdown_gpio, 0); // power up
+	usleep_range(1000, 1500); // 1ms from ACPI wait till IC is ready
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_MANUFACTURER:
+		readString(client, strBuf, 0x46, 8);
+		val->strval = strBuf;
+		break;
+	case POWER_SUPPLY_PROP_MODEL_NAME:
+		readString(client, strBuf, 0x52, 8);
+		val->strval = strBuf;
+		break;
+	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
+		sprintf(strBuf, "%04x", i2c_smbus_read_word_data(client, 0x44));
+		strBuf[4] = '\0';
+		val->strval = strBuf;
+		break;
+	case POWER_SUPPLY_PROP_CAPACITY:
+		val->intval = i2c_smbus_read_word_data(client, 0x28);
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+		val->intval = i2c_smbus_read_word_data(client, 0x3C) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		val->intval = i2c_smbus_read_word_data(client, 0x2C) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_NOW:
+		val->intval = i2c_smbus_read_word_data(client, 0x28)
+					* i2c_smbus_read_word_data(client, 0x2C) * 10;
+		break;
+	case POWER_SUPPLY_PROP_CYCLE_COUNT:
+		val->intval = i2c_smbus_read_word_data(client, 0x3A);
+		break;
+	case POWER_SUPPLY_PROP_STATUS:
+		if (i2c_smbus_read_byte_data(client, 0x02) & 0x01)
+			val->intval = POWER_SUPPLY_STATUS_CHARGING;
+		else
+			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		break;
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		readString(client, strBuf, 0x5A, 4);
+		if (strncmp(strBuf, "LION", 4) == 0)
+			val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
+		else
+			val->intval = POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
+		val->intval = i2c_smbus_read_word_data(client, 0x3E) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		val->intval = i2c_smbus_read_word_data(client, 0x20) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		val->intval = (int16_t)i2c_smbus_read_word_data(client, 0x24) * 1000;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	gpiod_set_value(srt_battery->powerdown_gpio, 1); // powerdown
+
+	return 0;
+}
+
+static const struct power_supply_desc srt_battery_power_supply_desc = {
+	.name = "surface-rt-battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = srt_battery_power_supply_props,
+	.num_properties = ARRAY_SIZE(srt_battery_power_supply_props),
+	.get_property = srt_battery_power_supply_get_property,
+};
+
+static int srt_battery_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct srt_battery_device *srt_battery;
+	struct power_supply_config psy_cfg = {};
+	int ret = -1;
+
+	srt_battery = devm_kzalloc(dev, sizeof(*srt_battery), GFP_KERNEL);
+	if (!srt_battery)
+		return -ENOMEM;
+
+	srt_battery->client = client;
+	srt_battery->dev = dev;
+
+	srt_battery->powerdown_gpio = devm_gpiod_get_optional(srt_battery->dev, "powerdown", GPIOD_OUT_LOW);
+	if (IS_ERR(srt_battery->powerdown_gpio)) {
+		ret = PTR_ERR(srt_battery->powerdown_gpio);
+		dev_err(srt_battery->dev, "Failed to get powerdown");
+		return ret;
+	}
+
+	psy_cfg.drv_data = srt_battery;
+
+	srt_battery->battery = devm_power_supply_register(srt_battery->dev, &srt_battery_power_supply_desc, &psy_cfg);
+
+	if (PTR_ERR_OR_ZERO(srt_battery->battery) < 0) {
+		dev_err(srt_battery->dev, "Failed to register power supply\n");
+		return ret;
+	}
+
+	i2c_set_clientdata(client, srt_battery);
+
+	gpiod_set_value(srt_battery->powerdown_gpio, 1); // powerdown
+
+	return 0;
+}
+
+static const struct i2c_device_id srt_battery_i2c_ids[] = {
+	{ "surface-rt-battery", 0 },
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, srt_battery_i2c_ids);
+
+static const struct of_device_id srt_battery_of_match[] = {
+	{ .compatible = "microsoft,surface-rt-battery", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, srt_battery_of_match);
+
+static struct i2c_driver srt_battery_driver = {
+	.driver = {
+		.name = "surface-rt-battery",
+		.of_match_table = of_match_ptr(srt_battery_of_match),
+	},
+	.probe = srt_battery_probe,
+	.id_table = srt_battery_i2c_ids,
+};
+module_i2c_driver(srt_battery_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jonas Schwöbel <jonasschwoebel@yahoo.de>");
+MODULE_DESCRIPTION("Surface RT Battery driver");