[PATCH v2 2/3] platform: arm64: Add Lenovo ThinkPad X13s EC driver
From: Clover
Date: Sat Sep 26 2026 - 15:55:20 EST
Add a standalone driver for the Lenovo ThinkPad X13s embedded controller,
providing keyboard-backlight control and notifications of firmware-driven
brightness changes. Keep the X13s-specific backlight, event and
power-management handling separate from the T14s driver.
Use STOP-separated command and response transfers and serialize EC
access, including keyboard-backlight read-modify-write operations.
Follow the EC command and power-state GPIO sequence described by the
X13s ACPI DSDT when entering and leaving low power.
Save the firmware-updated brightness in the EC on Fn+Space and restore
it on lid open, following the DSDT's SCMS(0x20) and SCMS(0x21) operations.
Also save software-selected brightness so lid opening does not reinstate
an older setting; this extends the DSDT's MLCS path, which does not
explicitly save it.
Defer event queries while suspended until normal resume, when the I2C
controller is usable again, and leave wake IRQ management to the I2C
core. Save the hardware backlight brightness before entering low power
and attempt to restore it on resume because the low-power transition
can reset it. Process deferred events afterwards so a lid-open restore
takes precedence over a snapshot taken after lid closure blanked the light.
This follows earlier X13s EC work by Konrad Dybcio and Steev Klimaszewski.
Assisted-by: LLM
Signed-off-by: Clover <alex@xxxxxxxxxxxxx>
---
diff --git a/MAINTAINERS b/MAINTAINERS
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27177,6 +27177,12 @@ THINKPAD T14S EMBEDDED CONTROLLER DRIVER
F: Documentation/devicetree/bindings/embedded-controller/lenovo,thinkpad-t14s-ec.yaml
F: drivers/platform/arm64/lenovo-thinkpad-t14s.c
+THINKPAD X13S EMBEDDED CONTROLLER DRIVER
+M: Clover <alex@xxxxxxxxxxxxx>
+S: Maintained
+F: Documentation/devicetree/bindings/embedded-controller/lenovo,thinkpad-x13s-ec.yaml
+F: drivers/platform/arm64/lenovo-thinkpad-x13s.c
+
THINKPAD LMI DRIVER
M: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
L: platform-driver-x86@xxxxxxxxxxxxxxx
diff --git a/drivers/platform/arm64/Kconfig b/drivers/platform/arm64/Kconfig
index e32e01b2a9bdd970d6f2b2bf6b051472c9a16103..c20b2fb40962f1d46e896ea7f7d0b16028f92f96 100644
--- a/drivers/platform/arm64/Kconfig
+++ b/drivers/platform/arm64/Kconfig
@@ -90,6 +90,22 @@ config EC_LENOVO_THINKPAD_T14S
Say M or Y here to include this support.
+config EC_LENOVO_THINKPAD_X13S
+ tristate "Lenovo ThinkPad X13s Embedded Controller driver"
+ depends on ARCH_QCOM || COMPILE_TEST
+ depends on I2C
+ depends on GPIOLIB
+ select NEW_LEDS
+ select LEDS_CLASS
+ select LEDS_BRIGHTNESS_HW_CHANGED
+ help
+ Driver for the embedded controller in the Lenovo ThinkPad X13s.
+ Provides keyboard backlight control, hardware brightness change
+ notifications and system sleep power sequencing with wake support.
+
+ To compile this driver as a module, choose M here: the module will
+ be called lenovo-thinkpad-x13s.
+
config EC_QCOM_HAMOA
tristate "Embedded Controller driver for Qualcomm Hamoa/Glymur reference devices"
depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/platform/arm64/Makefile b/drivers/platform/arm64/Makefile
index 7681be4a46e94e7cb80e50bcc5b724cb0961357b..23ed6eef7ce41a5f45d48f5f83b281ebbca94cbb 100644
--- a/drivers/platform/arm64/Makefile
+++ b/drivers/platform/arm64/Makefile
@@ -9,4 +9,5 @@ obj-$(CONFIG_EC_ACER_ASPIRE1) += acer-aspire1-ec.o
obj-$(CONFIG_EC_HUAWEI_GAOKUN) += huawei-gaokun-ec.o
obj-$(CONFIG_EC_LENOVO_YOGA_C630) += lenovo-yoga-c630.o
obj-$(CONFIG_EC_LENOVO_THINKPAD_T14S) += lenovo-thinkpad-t14s.o
+obj-$(CONFIG_EC_LENOVO_THINKPAD_X13S) += lenovo-thinkpad-x13s.o
obj-$(CONFIG_EC_QCOM_HAMOA) += qcom-hamoa-ec.o
diff --git a/drivers/platform/arm64/lenovo-thinkpad-x13s.c b/drivers/platform/arm64/lenovo-thinkpad-x13s.c
new file mode 100644
index 0000000000000000000000000000000000000000..708f909f787805d9832c2ff4aac29a8d8d52d0bb
--- /dev/null
+++ b/drivers/platform/arm64/lenovo-thinkpad-x13s.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Lenovo ThinkPad X13s embedded controller */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/container_of.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/leds.h>
+#include <linux/lockdep.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/slab.h>
+
+#define X13S_EC_CMD_READ 0x02
+#define X13S_EC_CMD_WRITE 0x03
+#define X13S_EC_CMD_EVENT 0xf0
+#define X13S_EC_REG_POWER_STATE 0x80
+#define X13S_EC_POWER_STATE_ENTER 0x55
+#define X13S_EC_POWER_STATE_EXIT 0xaa
+#define X13S_EC_REG_KBD_BACKLIGHT 0xc0
+#define X13S_EC_BACKLIGHT_MASK GENMASK(5, 4)
+#define X13S_EC_REG_KBD_BACKLIGHT_SAVED 0x15
+#define X13S_EC_BACKLIGHT_SAVED_MASK GENMASK(2, 1)
+#define X13S_EC_EVENT_FN_SPACE 0x1f
+#define X13S_EC_EVENT_LID_OPEN 0x52
+
+struct x13s_ec {
+ struct i2c_client *client;
+ struct gpio_desc *power_state;
+ /* Serializes EC transactions, backlight RMW and suspend/event state. */
+ struct mutex lock;
+ struct led_classdev led;
+ enum led_brightness saved_brightness;
+ bool suspended;
+ bool event_pending;
+};
+
+/*
+ * Each single-message transfer ends in STOP. Hold the bus segment across
+ * both halves so another client cannot interleave them. Keep the 10 ms
+ * post-command settling delay, including on failure.
+ */
+static int x13s_read(struct x13s_ec *ec, u8 cmd, u8 reg, u8 *value)
+{
+ struct i2c_client *client = ec->client;
+ u8 buf[] = { cmd, reg, 0, 1 };
+ struct i2c_msg request = {
+ .addr = client->addr,
+ .flags = I2C_M_STOP,
+ .len = sizeof(buf),
+ .buf = buf,
+ };
+ struct i2c_msg response = {
+ .addr = client->addr,
+ .flags = I2C_M_RD,
+ .len = 1,
+ .buf = value,
+ };
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ if (ec->suspended)
+ return -EBUSY;
+
+ i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
+ ret = __i2c_transfer(client->adapter, &request, 1);
+ if (ret == 1)
+ ret = __i2c_transfer(client->adapter, &response, 1);
+ ret = ret == 1 ? 0 : (ret < 0 ? ret : -EIO);
+ i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
+ fsleep(10000);
+ return ret;
+}
+
+/* Also used by normal PM callbacks while ordinary EC access is blocked. */
+static int x13s_write(struct x13s_ec *ec, u8 reg, u8 value)
+{
+ u8 buf[] = { X13S_EC_CMD_WRITE, reg, 0, 1, value };
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+
+ ret = i2c_master_send(ec->client, buf, sizeof(buf));
+ ret = ret == sizeof(buf) ? 0 : (ret < 0 ? ret : -EIO);
+ fsleep(10000);
+ return ret;
+}
+
+static int x13s_brightness(struct x13s_ec *ec)
+{
+ u8 value;
+ int ret;
+
+ ret = x13s_read(ec, X13S_EC_CMD_READ, X13S_EC_REG_KBD_BACKLIGHT, &value);
+ if (ret)
+ return ret;
+
+ ret = FIELD_GET(X13S_EC_BACKLIGHT_MASK, value);
+ return ret == 3 ? -EINVAL : ret;
+}
+
+static enum led_brightness x13s_brightness_get(struct led_classdev *led)
+{
+ struct x13s_ec *ec = container_of(led, struct x13s_ec, led);
+ int ret;
+
+ mutex_lock(&ec->lock);
+ ret = x13s_brightness(ec);
+ mutex_unlock(&ec->lock);
+ return ret;
+}
+
+static int x13s_set_brightness_locked(struct x13s_ec *ec,
+ enum led_brightness brightness)
+{
+ u8 old, new;
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ if (brightness > 2)
+ return -EINVAL;
+
+ ret = x13s_read(ec, X13S_EC_CMD_READ, X13S_EC_REG_KBD_BACKLIGHT, &old);
+ if (ret)
+ return ret;
+ /* Never interpret or overwrite a reserved current brightness. */
+ if (FIELD_GET(X13S_EC_BACKLIGHT_MASK, old) == 3)
+ return -EINVAL;
+ new = (old & ~X13S_EC_BACKLIGHT_MASK) |
+ FIELD_PREP(X13S_EC_BACKLIGHT_MASK, brightness);
+ return x13s_write(ec, X13S_EC_REG_KBD_BACKLIGHT, new);
+}
+
+/* SCMS(0x20): save the brightness obtained from C0 in the EC. */
+static int x13s_save_brightness_locked(struct x13s_ec *ec,
+ enum led_brightness brightness)
+{
+ u8 value;
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ ret = x13s_read(ec, X13S_EC_CMD_READ, X13S_EC_REG_KBD_BACKLIGHT_SAVED,
+ &value);
+ if (ret)
+ return ret;
+
+ value &= ~X13S_EC_BACKLIGHT_SAVED_MASK;
+ value |= FIELD_PREP(X13S_EC_BACKLIGHT_SAVED_MASK, brightness);
+ return x13s_write(ec, X13S_EC_REG_KBD_BACKLIGHT_SAVED, value);
+}
+
+/* SCMS(0x21): restore C0 from the EC's saved brightness. */
+static int x13s_restore_brightness_locked(struct x13s_ec *ec)
+{
+ u8 value;
+ int brightness, ret;
+
+ lockdep_assert_held(&ec->lock);
+ ret = x13s_read(ec, X13S_EC_CMD_READ, X13S_EC_REG_KBD_BACKLIGHT_SAVED,
+ &value);
+ if (ret)
+ return ret;
+
+ brightness = FIELD_GET(X13S_EC_BACKLIGHT_SAVED_MASK, value);
+ ret = x13s_set_brightness_locked(ec, brightness);
+ return ret ? ret : brightness;
+}
+
+static int x13s_brightness_set(struct led_classdev *led,
+ enum led_brightness brightness)
+{
+ struct x13s_ec *ec = container_of(led, struct x13s_ec, led);
+ int ret;
+
+ mutex_lock(&ec->lock);
+ ret = x13s_set_brightness_locked(ec, brightness);
+ /* Keep software selections across the EC's lid blank/restore cycle. */
+ if (!ret)
+ ret = x13s_save_brightness_locked(ec, brightness);
+ mutex_unlock(&ec->lock);
+ return ret;
+}
+
+static void x13s_refresh_brightness(struct x13s_ec *ec)
+{
+ int brightness, ret;
+
+ lockdep_assert_held(&ec->lock);
+ /* Firmware owns the transition; save its result as _Q1F does. */
+ brightness = x13s_brightness(ec);
+ if (brightness < 0) {
+ dev_err_ratelimited(&ec->client->dev,
+ "Backlight refresh failed: %d\n", brightness);
+ return;
+ }
+ ret = x13s_save_brightness_locked(ec, brightness);
+ if (ret)
+ dev_err_ratelimited(&ec->client->dev,
+ "Backlight save failed: %d\n", ret);
+ led_classdev_notify_brightness_hw_changed(&ec->led, brightness);
+}
+
+static void x13s_query_event(struct x13s_ec *ec)
+{
+ u8 event;
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ /* One query per interrupt, with no event-draining loop or retry. */
+ ret = x13s_read(ec, X13S_EC_CMD_EVENT, 0, &event);
+ if (ret) {
+ dev_err_ratelimited(&ec->client->dev, "Event query failed: %d\n", ret);
+ return;
+ }
+ if (event == X13S_EC_EVENT_FN_SPACE) {
+ x13s_refresh_brightness(ec);
+ } else if (event == X13S_EC_EVENT_LID_OPEN) {
+ ret = x13s_restore_brightness_locked(ec);
+ if (ret < 0) {
+ dev_err_ratelimited(&ec->client->dev,
+ "Backlight lid restore failed: %d\n", ret);
+ return;
+ }
+ ec->led.brightness = ret;
+ led_classdev_notify_brightness_hw_changed(&ec->led, ret);
+ }
+}
+
+static void x13s_process_pending_event(struct x13s_ec *ec)
+{
+ lockdep_assert_held(&ec->lock);
+ if (ec->event_pending) {
+ ec->event_pending = false;
+ x13s_query_event(ec);
+ }
+}
+
+static irqreturn_t x13s_irq(int irq, void *data)
+{
+ struct x13s_ec *ec = data;
+
+ mutex_lock(&ec->lock);
+ /* Coalesce suspended IRQs into one query; never access I2C here. */
+ if (ec->suspended)
+ ec->event_pending = true;
+ else
+ x13s_query_event(ec);
+ mutex_unlock(&ec->lock);
+ return IRQ_HANDLED;
+}
+
+static int x13s_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct x13s_ec *ec;
+ int ret;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -EOPNOTSUPP;
+ if (client->irq <= 0)
+ return dev_err_probe(dev, -EINVAL, "Missing event IRQ\n");
+ if (irq_get_trigger_type(client->irq) != IRQ_TYPE_EDGE_FALLING)
+ return dev_err_probe(dev, -EINVAL, "Expected falling-edge IRQ\n");
+
+ ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
+ if (!ec)
+ return -ENOMEM;
+ ec->client = client;
+ ret = devm_mutex_init(dev, &ec->lock);
+ if (ret)
+ return ret;
+ i2c_set_clientdata(client, ec);
+
+ ec->power_state = devm_gpiod_get(dev, "power-state", GPIOD_OUT_HIGH);
+ if (IS_ERR(ec->power_state))
+ return dev_err_probe(dev, PTR_ERR(ec->power_state),
+ "Failed to acquire power-state GPIO high\n");
+
+ ec->led.name = "platform::kbd_backlight";
+ ec->led.max_brightness = 2;
+ ec->led.flags = LED_BRIGHT_HW_CHANGED | LED_RETAIN_AT_SHUTDOWN;
+ ec->led.brightness_get = x13s_brightness_get;
+ ec->led.brightness_set_blocking = x13s_brightness_set;
+ ret = devm_led_classdev_register(dev, &ec->led);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to register keyboard backlight\n");
+
+ /* Devres synchronizes the IRQ before unregistering the LED. */
+ ret = devm_request_threaded_irq(dev, client->irq, NULL, x13s_irq,
+ IRQF_ONESHOT, dev_name(dev), ec);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to request event IRQ\n");
+
+ /* The I2C core manages the wake IRQ described by wakeup-source. */
+ return 0;
+}
+
+static int x13s_power_gpio(struct x13s_ec *ec, int value)
+{
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ ret = gpiod_set_value_cansleep(ec->power_state, value);
+ if (ret)
+ dev_err(&ec->client->dev, "Failed to set power-state GPIO to %d: %d\n",
+ value, ret);
+ return ret;
+}
+
+static void x13s_exit_low_power(struct x13s_ec *ec)
+{
+ int ret;
+
+ lockdep_assert_held(&ec->lock);
+ x13s_power_gpio(ec, 1);
+ /* DSDT: GPIO176 high, Sleep(10), then register 0x80 <- 0xaa. */
+ fsleep(10000);
+ ret = x13s_write(ec, X13S_EC_REG_POWER_STATE, X13S_EC_POWER_STATE_EXIT);
+ if (ret)
+ dev_err(&ec->client->dev, "Failed to exit low power: %d\n", ret);
+
+ /* Resume ordinary access even if the EC exit attempt failed. */
+ ec->suspended = false;
+}
+
+static int x13s_suspend(struct device *dev)
+{
+ struct x13s_ec *ec = dev_get_drvdata(dev);
+ int ret;
+
+ /* Finish in-flight access while the GENI parent is still usable. */
+ mutex_lock(&ec->lock);
+ if (ec->suspended)
+ goto out;
+ /* Keep the previous snapshot if reading the hardware fails. */
+ ret = x13s_brightness(ec);
+ if (ret < 0)
+ dev_err(dev, "Failed to save backlight brightness: %d\n", ret);
+ else
+ ec->saved_brightness = ret;
+
+ /* DSDT: register 0x80 <- 0x55, then GPIO176 low. */
+ ret = x13s_write(ec, X13S_EC_REG_POWER_STATE, X13S_EC_POWER_STATE_ENTER);
+ if (ret)
+ dev_err(dev, "Failed to enter low power: %d\n", ret);
+ else
+ x13s_power_gpio(ec, 0);
+ /* Defer event queries throughout host suspend, even on EC failure. */
+ ec->suspended = true;
+out:
+ mutex_unlock(&ec->lock);
+ return 0;
+}
+
+static int x13s_resume(struct device *dev)
+{
+ struct x13s_ec *ec = dev_get_drvdata(dev);
+ int ret;
+
+ /*
+ * Normal resume runs after the adapter and its GENI parent. In
+ * particular, device_resume_early() has re-enabled runtime PM:
+ * GENI's resume_noirq() alone is not sufficient for I2C transfers.
+ * Consume the pending query under the IRQ thread's mutex, without
+ * a worker that could race a new IRQ or the next suspend.
+ */
+ mutex_lock(&ec->lock);
+ x13s_exit_low_power(ec);
+ ret = x13s_set_brightness_locked(ec, ec->saved_brightness);
+ if (ret)
+ dev_err(dev, "Failed to restore backlight brightness: %d\n", ret);
+ else
+ /* A software restore is not a hardware brightness change. */
+ ec->led.brightness = ec->saved_brightness;
+
+ /* A deferred lid-open restore must supersede the PM snapshot. */
+ x13s_process_pending_event(ec);
+ mutex_unlock(&ec->lock);
+ return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(x13s_pm_ops, x13s_suspend, x13s_resume);
+
+static const struct of_device_id x13s_of_match[] = {
+ { .compatible = "lenovo,thinkpad-x13s-ec" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, x13s_of_match);
+
+static struct i2c_driver x13s_driver = {
+ .probe = x13s_probe,
+ .driver = {
+ .name = "thinkpad-x13s-ec",
+ .of_match_table = x13s_of_match,
+ .pm = pm_sleep_ptr(&x13s_pm_ops),
+ },
+};
+module_i2c_driver(x13s_driver);
+
+MODULE_DESCRIPTION("Lenovo ThinkPad X13s Embedded Controller");
+MODULE_LICENSE("GPL");