[PATCH v6 6/7] power: supply: Add driver for ASUS Transformer battery

Svyatoslav Ryhel
2026-05-02T12:41:24Z

Driver implements one battery cell per EC controller and supports reading
of battery status for ASUS Transformer's pad and mobile dock.

Co-developed-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
drivers/power/supply/Kconfig | 11 +
drivers/power/supply/Makefile | 1 +
.../supply/asus-transformer-ec-battery.c | 272 ++++++++++++++++++
3 files changed, 284 insertions(+)
create mode 100644 drivers/power/supply/asus-transformer-ec-battery.c

diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 83392ed6a8da..1dc3d0b2e021 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -122,6 +122,17 @@ config BATTERY_CHAGALL
This driver can also be built as a module. If so, the module will be
called chagall-battery.

+config BATTERY_ASUS_TRANSFORMER_EC
+ tristate "Asus Transformer's battery driver"
+ depends on MFD_ASUS_TRANSFORMER_EC
+ help
+ Say Y to enable support for battery status access on Tegra based
+ ASUS Transformer devices.
+
+ This sub-driver supports battery cells found in Asus Transformer
+ tablets and mobile docks and controlled by a special embedded
+ controller.
+
config BATTERY_CPCAP
tristate "Motorola CPCAP PMIC battery driver"
depends on MFD_CPCAP && IIO
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 7ee839dca7f3..1313f367715c 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_TEST_POWER) += test_power.o
obj-$(CONFIG_BATTERY_88PM860X) += 88pm860x_battery.o
obj-$(CONFIG_CHARGER_ADP5061) += adp5061.o
obj-$(CONFIG_BATTERY_ACT8945A) += act8945a_charger.o
+obj-$(CONFIG_BATTERY_ASUS_TRANSFORMER_EC) += asus-transformer-ec-battery.o
obj-$(CONFIG_BATTERY_AXP20X) += axp20x_battery.o
obj-$(CONFIG_CHARGER_AXP20X) += axp20x_ac_power.o
obj-$(CONFIG_BATTERY_CHAGALL) += chagall-battery.o
diff --git a/drivers/power/supply/asus-transformer-ec-battery.c b/drivers/power/supply/asus-transformer-ec-battery.c
new file mode 100644
index 000000000000..aefcd3fed6fe
--- /dev/null
+++ b/drivers/power/supply/asus-transformer-ec-battery.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/array_size.h>
+#include <linux/devm-helpers.h>
+#include <linux/err.h>
+#include <linux/mfd/asus-transformer-ec.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/property.h>
+#include <linux/unaligned.h>
+
+#define ASUSEC_BATTERY_DATA_FRESH_MSEC 5000
+
+#define ASUSEC_BATTERY_DISCHARGING 0x40
+#define ASUSEC_BATTERY_FULL_CHARGED 0x20
+#define ASUSEC_BATTERY_NOT_CHARGING 0x10
+
+#define TEMP_CELSIUS_OFFSET 2731
+
+struct asus_ec_battery_data {
+ const struct asusec_info *ec;
+ struct power_supply *battery;
+ struct power_supply_desc psy_desc;
+ struct delayed_work poll_work;
+ struct mutex battery_lock; /* for data refresh */
+ unsigned long batt_data_ts;
+ int last_state;
+ u8 batt_data[DOCKRAM_ENTRY_BUFSIZE];
+};
+
+static int asus_ec_battery_refresh(struct asus_ec_battery_data *priv)
+{
+ int ret = 0;
+
+ guard(mutex)(&priv->battery_lock);
+
+ if (time_before(jiffies, priv->batt_data_ts))
+ return ret;
+
+ ret = asus_dockram_read(priv->ec->dockram, ASUSEC_DOCKRAM_BATT_CTL,
+ priv->batt_data);
+ if (ret < 0)
+ return ret;
+
+ priv->batt_data_ts = jiffies +
+ msecs_to_jiffies(ASUSEC_BATTERY_DATA_FRESH_MSEC);
+
+ return ret;
+}
+
+static enum power_supply_property asus_ec_battery_properties[] = {
+ POWER_SUPPLY_PROP_STATUS,
+ POWER_SUPPLY_PROP_VOLTAGE_MAX,
+ POWER_SUPPLY_PROP_CURRENT_MAX,
+ POWER_SUPPLY_PROP_TEMP,
+ POWER_SUPPLY_PROP_VOLTAGE_NOW,
+ POWER_SUPPLY_PROP_CURRENT_NOW,
+ POWER_SUPPLY_PROP_CAPACITY,
+ POWER_SUPPLY_PROP_CHARGE_NOW,
+ POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW,
+ POWER_SUPPLY_PROP_TIME_TO_FULL_NOW,
+ POWER_SUPPLY_PROP_PRESENT,
+};
+
+static const unsigned int asus_ec_battery_prop_offs[] = {
+ [POWER_SUPPLY_PROP_STATUS] = 1,
+ [POWER_SUPPLY_PROP_VOLTAGE_MAX] = 3,
+ [POWER_SUPPLY_PROP_CURRENT_MAX] = 5,
+ [POWER_SUPPLY_PROP_TEMP] = 7,
+ [POWER_SUPPLY_PROP_VOLTAGE_NOW] = 9,
+ [POWER_SUPPLY_PROP_CURRENT_NOW] = 11,
+ [POWER_SUPPLY_PROP_CAPACITY] = 13,
+ [POWER_SUPPLY_PROP_CHARGE_NOW] = 15,
+ [POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW] = 17,
+ [POWER_SUPPLY_PROP_TIME_TO_FULL_NOW] = 19,
+};
+
+static int asus_ec_battery_get_value(struct asus_ec_battery_data *priv,
+ enum power_supply_property psp)
+{
+ int ret, offs;
+
+ if (psp >= ARRAY_SIZE(asus_ec_battery_prop_offs))
+ return -EINVAL;
+
+ offs = asus_ec_battery_prop_offs[psp];
+ if (!offs)
+ return -EINVAL;
+
+ ret = asus_ec_battery_refresh(priv);
+ if (ret < 0)
+ return ret;
+
+ if (offs >= priv->batt_data[0])
+ return -ENODATA;
+
+ return get_unaligned_le16(priv->batt_data + offs);
+}
+
+static int asus_ec_battery_get_property(struct power_supply *psy,
+ enum power_supply_property psp,
+ union power_supply_propval *val)
+{
+ struct asus_ec_battery_data *priv = power_supply_get_drvdata(psy);
+ int ret;
+
+ switch (psp) {
+ case POWER_SUPPLY_PROP_PRESENT:
+ val->intval = 1;
+ break;
+
+ default:
+ ret = asus_ec_battery_get_value(priv, psp);
+ if (ret < 0)
+ return ret;
+
+ val->intval = (s16)ret;
+
+ switch (psp) {
+ case POWER_SUPPLY_PROP_STATUS:
+ if (ret & ASUSEC_BATTERY_FULL_CHARGED)
+ val->intval = POWER_SUPPLY_STATUS_FULL;
+ else if (ret & ASUSEC_BATTERY_NOT_CHARGING)
+ val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
+ else if (ret & ASUSEC_BATTERY_DISCHARGING)
+ val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+ else
+ val->intval = POWER_SUPPLY_STATUS_CHARGING;
+ break;
+
+ case POWER_SUPPLY_PROP_TEMP:
+ val->intval -= TEMP_CELSIUS_OFFSET;
+ break;
+
+ case POWER_SUPPLY_PROP_CHARGE_NOW:
+ case POWER_SUPPLY_PROP_CURRENT_NOW:
+ case POWER_SUPPLY_PROP_CURRENT_MAX:
+ case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+ case POWER_SUPPLY_PROP_VOLTAGE_MAX:
+ val->intval *= 1000;
+ break;
+
+ case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
+ case POWER_SUPPLY_PROP_TIME_TO_FULL_NOW:
+ val->intval *= 60;
+ break;
+
+ default:
+ break;
+ }
+
+ break;
+ }
+
+ return 0;
+}
+
+static void asus_ec_battery_poll_work(struct work_struct *work)
+{
+ struct asus_ec_battery_data *priv =
+ container_of(work, struct asus_ec_battery_data, poll_work.work);
+ int state;
+
+ state = asus_ec_battery_get_value(priv, POWER_SUPPLY_PROP_STATUS);
+ if (state < 0)
+ return;
+
+ if (state & ASUSEC_BATTERY_FULL_CHARGED)
+ state = POWER_SUPPLY_STATUS_FULL;
+ else if (state & ASUSEC_BATTERY_DISCHARGING)
+ state = POWER_SUPPLY_STATUS_DISCHARGING;
+ else
+ state = POWER_SUPPLY_STATUS_CHARGING;
+
+ if (priv->last_state != state) {
+ priv->last_state = state;
+ power_supply_changed(priv->battery);
+ }
+
+ /* continuously send uevent notification */
+ schedule_delayed_work(&priv->poll_work,
+ msecs_to_jiffies(ASUSEC_BATTERY_DATA_FRESH_MSEC));
+}
+
+static const struct power_supply_desc asus_ec_battery_desc = {
+ .name = "asus-ec-battery",
+ .type = POWER_SUPPLY_TYPE_BATTERY,
+ .properties = asus_ec_battery_properties,
+ .num_properties = ARRAY_SIZE(asus_ec_battery_properties),
+ .get_property = asus_ec_battery_get_property,
+ .external_power_changed = power_supply_changed,
+};
+
+static int asus_ec_battery_probe(struct platform_device *pdev)
+{
+ struct asus_ec_battery_data *priv;
+ struct device *dev = &pdev->dev;
+ struct power_supply_config cfg = { };
+ int ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, priv);
+
+ mutex_init(&priv->battery_lock);
+
+ priv->ec = cell_to_ec(pdev);
+ priv->batt_data_ts = jiffies - 1;
+ priv->last_state = POWER_SUPPLY_STATUS_UNKNOWN;
+
+ cfg.fwnode = dev_fwnode(dev->parent);
+ cfg.drv_data = priv;
+
+ memcpy(&priv->psy_desc, &asus_ec_battery_desc, sizeof(priv->psy_desc));
+ priv->psy_desc.name = devm_kasprintf(dev, GFP_KERNEL, "%s-battery",
+ priv->ec->name);
+
+ priv->battery = devm_power_supply_register(dev, &priv->psy_desc, &cfg);
+ if (IS_ERR(priv->battery))
+ return dev_err_probe(dev, PTR_ERR(priv->battery),
+ "Failed to register power supply\n");
+
+ ret = devm_delayed_work_autocancel(dev, &priv->poll_work,
+ asus_ec_battery_poll_work);
+ if (ret)
+ return ret;
+
+ schedule_delayed_work(&priv->poll_work,
+ msecs_to_jiffies(ASUSEC_BATTERY_DATA_FRESH_MSEC));
+
+ return 0;
+}
+
+static int __maybe_unused asus_ec_battery_suspend(struct device *dev)
+{
+ struct asus_ec_battery_data *priv = dev_get_drvdata(dev);
+
+ cancel_delayed_work_sync(&priv->poll_work);
+
+ return 0;
+}
+
+static int __maybe_unused asus_ec_battery_resume(struct device *dev)
+{
+ struct asus_ec_battery_data *priv = dev_get_drvdata(dev);
+
+ schedule_delayed_work(&priv->poll_work,
+ msecs_to_jiffies(ASUSEC_BATTERY_DATA_FRESH_MSEC));
+
+ return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(asus_ec_battery_pm_ops,
+ asus_ec_battery_suspend, asus_ec_battery_resume);
+
+static struct platform_driver asus_ec_battery_driver = {
+ .driver = {
+ .name = "asus-transformer-ec-battery",
+ .pm = &asus_ec_battery_pm_ops,
+ },
+ .probe = asus_ec_battery_probe,
+};
+module_platform_driver(asus_ec_battery_driver);
+
+MODULE_AUTHOR("Michał Mirosław <mirq-linux@rere.qmqm.pl>");
+MODULE_AUTHOR("Svyatoslav Ryhel <clamor95@gmail.com>");
+MODULE_DESCRIPTION("ASUS Transformer's battery driver");