Documentation/hwmon/index.rst | 1 + Documentation/hwmon/lattepanda-sigma-ec.rst | 61 ++++ MAINTAINERS | 7 + drivers/hwmon/Kconfig | 17 + drivers/hwmon/Makefile | 1 + drivers/hwmon/lattepanda-sigma-ec.c | 329 ++++++++++++++++++++ 6 files changed, 416 insertions(+) create mode 100644 Documentation/hwmon/lattepanda-sigma-ec.rst create mode 100644 drivers/hwmon/lattepanda-sigma-ec.c
The LattePanda Sigma is an x86 single-board computer made by DFRobot,
featuring an Intel Core i5-1340P and an ITE IT8613E Embedded Controller
that manages fan speed and thermal monitoring.
The BIOS declares the ACPI Embedded Controller (PNP0C09) with _STA
returning 0 and provides only stub ECRD/ECWT methods. Since the kernel's
ACPI EC subsystem never initializes, ec_read() is not available and
direct port I/O to the standard ACPI EC ports (0x62/0x66) is used. As
ACPI never accesses the EC, no ACPI Global Lock or namespace mutex is
required.
The driver exposes:
- CPU fan speed (RPM, read-only)
- Board temperature (unsigned 8-bit, degrees Celsius)
- CPU proximity temperature (unsigned 8-bit, degrees Celsius)
DMI matching restricts the driver to verified LattePanda Sigma hardware
with BIOS version 5.27. A 'force' module parameter allows loading on
untested BIOS versions while still requiring vendor/product match.
The EC register map was discovered through firmware reverse engineering
and confirmed by physical testing.
Signed-off-by: Mariano Abad <weimaraner@gmail.com>
---
Changes in v2:
- Add entry to Documentation/hwmon/index.rst
- Move reverse engineering notes and ACPI explanation from .rst
into driver source comments
- Restrict DMI match to BIOS version 5.27; add 'force' module
parameter for untested versions
- Document why no ACPI lock is needed: DSDT analysis shows _STA
returns 0 and ECRD/ECWT are stubs, so firmware never accesses
the EC ports
- Remove driver mutex: the hwmon with_info API already serializes
all sysfs callbacks
- Keep udelay() for EC polling: usleep_range() was tested but
caused EC protocol failures; approach matches the kernel ACPI
EC driver (drivers/acpi/ec.c)
- Clarify temperature values are unsigned 8-bit
- Register platform driver before platform device
- Link to v1: https://lore.kernel.org/linux-hwmon/20260301023707.1184592-1-weimaraner@gmail.com/
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/lattepanda-sigma-ec.rst | 61 ++++
MAINTAINERS | 7 +
drivers/hwmon/Kconfig | 17 +
drivers/hwmon/Makefile | 1 +
drivers/hwmon/lattepanda-sigma-ec.c | 329 ++++++++++++++++++++
6 files changed, 416 insertions(+)
create mode 100644 Documentation/hwmon/lattepanda-sigma-ec.rst
create mode 100644 drivers/hwmon/lattepanda-sigma-ec.c
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index d91dbb20c..dff283064 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
kbatt
kfan
lan966x
+ lattepanda-sigma-ec
lineage-pem
lm25066
lm63
diff --git a/Documentation/hwmon/lattepanda-sigma-ec.rst b/Documentation/hwmon/lattepanda-sigma-ec.rst
new file mode 100644
index 000000000..8a521ee1f
--- /dev/null
+++ b/Documentation/hwmon/lattepanda-sigma-ec.rst
@@ -0,0 +1,61 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver lattepanda-sigma-ec
+=================================
+
+Supported systems:
+
+ * LattePanda Sigma (Intel 13th Gen i5-1340P)
+
+ DMI vendor: LattePanda
+
+ DMI product: LattePanda Sigma
+
+ BIOS version: 5.27 (verified)
+
+ Datasheet: Not available (EC registers discovered empirically)
+
+Author: Mariano Abad <weimaraner@gmail.com>
+
+Description
+-----------
+
+This driver provides hardware monitoring for the LattePanda Sigma
+single-board computer made by DFRobot. The board uses an ITE IT8613E
+Embedded Controller to manage a CPU cooling fan and thermal sensors.
+
+The BIOS declares the ACPI Embedded Controller (``PNP0C09``) with
+``_STA`` returning 0, preventing the kernel's ACPI EC subsystem from
+initializing. This driver reads the EC directly via the standard ACPI
+EC I/O ports (``0x62`` data, ``0x66`` command/status).
+
+Sysfs attributes
+----------------
+
+======================= ===============================================
+``fan1_input`` Fan speed in RPM (EC registers 0x2E:0x2F,
+ 16-bit big-endian)
+``fan1_label`` "CPU Fan"
+``temp1_input`` Board/ambient temperature in millidegrees
+ Celsius (EC register 0x60, unsigned)
+``temp1_label`` "Board Temp"
+``temp2_input`` CPU proximity temperature in millidegrees
+ Celsius (EC register 0x70, unsigned)
+``temp2_label`` "CPU Temp"
+======================= ===============================================
+
+Module parameters
+-----------------
+
+``force`` (bool, default false)
+ Force loading on BIOS versions other than 5.27. The driver still
+ requires DMI vendor and product name matching.
+
+Known limitations
+-----------------
+
+* Fan speed control is not supported. The fan is always under EC
+ automatic control.
+* The EC register map was verified only on BIOS version 5.27.
+ Other versions may use different register offsets; use the ``force``
+ parameter at your own risk.
diff --git a/MAINTAINERS b/MAINTAINERS
index 96e97d25e..7b0c5bb5d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14414,6 +14414,13 @@ F: drivers/net/wan/framer/
F: drivers/pinctrl/pinctrl-pef2256.c
F: include/linux/framer/
+LATTEPANDA SIGMA EC HARDWARE MONITOR DRIVER
+M: Mariano Abad <weimaraner@gmail.com>
+L: linux-hwmon@vger.kernel.org
+S: Maintained
+F: Documentation/hwmon/lattepanda-sigma-ec.rst
+F: drivers/hwmon/lattepanda-sigma-ec.c
+
LASI 53c700 driver for PARISC
M: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
L: linux-scsi@vger.kernel.org
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 41c381764..f2e2ee96f 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -990,6 +990,23 @@ config SENSORS_LAN966X
This driver can also be built as a module. If so, the module
will be called lan966x-hwmon.
+config SENSORS_LATTEPANDA_SIGMA_EC
+ tristate "LattePanda Sigma EC hardware monitoring"
+ depends on X86
+ depends on DMI
+ depends on HAS_IOPORT
+ help
+ If you say yes here you get support for the hardware monitoring
+ features of the Embedded Controller on LattePanda Sigma
+ single-board computers, including CPU fan speed (RPM) and
+ board and CPU temperatures.
+
+ The driver reads the EC directly via ACPI EC I/O ports and
+ uses DMI matching to ensure it only loads on supported hardware.
+
+ This driver can also be built as a module. If so, the module
+ will be called lattepanda-sigma-ec.
+
config SENSORS_LENOVO_EC
tristate "Sensor reader for Lenovo ThinkStations"
depends on X86
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index eade8e3b1..0372fedbb 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_SENSORS_K10TEMP) += k10temp.o
obj-$(CONFIG_SENSORS_KBATT) += kbatt.o
obj-$(CONFIG_SENSORS_KFAN) += kfan.o
obj-$(CONFIG_SENSORS_LAN966X) += lan966x-hwmon.o
+obj-$(CONFIG_SENSORS_LATTEPANDA_SIGMA_EC) += lattepanda-sigma-ec.o
obj-$(CONFIG_SENSORS_LENOVO_EC) += lenovo-ec-sensors.o
obj-$(CONFIG_SENSORS_LINEAGE) += lineage-pem.o
obj-$(CONFIG_SENSORS_LOCHNAGAR) += lochnagar-hwmon.o
diff --git a/drivers/hwmon/lattepanda-sigma-ec.c b/drivers/hwmon/lattepanda-sigma-ec.c
new file mode 100644
index 000000000..2ba51a20d
--- /dev/null
+++ b/drivers/hwmon/lattepanda-sigma-ec.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for LattePanda Sigma EC.
+ *
+ * The LattePanda Sigma is an x86 SBC made by DFRobot with an ITE IT8613E
+ * Embedded Controller that manages a CPU fan and thermal sensors.
+ *
+ * The BIOS declares the ACPI Embedded Controller (PNP0C09) with _STA
+ * returning 0 and provides only stub ECRD/ECWT methods that return Zero
+ * for all registers. Since the kernel's ACPI EC subsystem never initializes,
+ * ec_read() is not available and direct port I/O to the standard ACPI EC
+ * ports (0x62/0x66) is used instead.
+ *
+ * Because ACPI never initializes the EC, there is no concurrent firmware
+ * access to these ports, and no ACPI Global Lock or namespace mutex is
+ * required. The hwmon with_info API serializes all sysfs callbacks,
+ * so no additional driver-level locking is needed.
+ *
+ * The EC register map was discovered by dumping all 256 registers,
+ * identifying those that change in real-time, and validating by physically
+ * stopping the fan and observing the RPM register drop to zero. The map
+ * has been verified on BIOS version 5.27; other versions may differ.
+ *
+ * Copyright (c) 2026 Mariano Abad <weimaraner@gmail.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/dmi.h>
+#include <linux/hwmon.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define DRIVER_NAME "lattepanda_sigma_ec"
+
+/* EC I/O ports (standard ACPI EC interface) */
+#define EC_DATA_PORT 0x62
+#define EC_CMD_PORT 0x66 /* also status port */
+
+/* EC commands */
+#define EC_CMD_READ 0x80
+
+/* EC status register bits */
+#define EC_STATUS_OBF 0x01 /* Output Buffer Full */
+#define EC_STATUS_IBF 0x02 /* Input Buffer Full */
+
+/* EC register offsets for LattePanda Sigma (BIOS 5.27) */
+#define EC_REG_FAN_RPM_HI 0x2E
+#define EC_REG_FAN_RPM_LO 0x2F
+#define EC_REG_TEMP_BOARD 0x60
+#define EC_REG_TEMP_CPU 0x70
+#define EC_REG_FAN_DUTY 0x93
+
+/*
+ * EC polling uses udelay() because the EC typically responds within a
+ * few microseconds. The kernel's own ACPI EC driver (drivers/acpi/ec.c)
+ * likewise uses udelay() for busy-polling with a per-poll delay of 550us.
+ *
+ * usleep_range() was tested but caused EC protocol failures: the EC
+ * clears its status flags within microseconds, and sleeping for 50-100us
+ * between polls allowed the flags to transition past the expected state.
+ *
+ * The worst-case total busy-wait of 25ms covers EC recovery after errors.
+ * In practice the EC responds within 10us so the loop exits immediately.
+ */
+#define EC_TIMEOUT_US 25000
+#define EC_POLL_US 1
+
+static bool force;
+module_param(force, bool, 0444);
+MODULE_PARM_DESC(force,
+ "Force loading on untested BIOS versions (default: false)");
+
+static struct platform_device *lps_ec_pdev;
+
+static int ec_wait_ibf_clear(void)
+{
+ int i;
+
+ for (i = 0; i < EC_TIMEOUT_US; i++) {
+ if (!(inb(EC_CMD_PORT) & EC_STATUS_IBF))
+ return 0;
+ udelay(EC_POLL_US);
+ }
+ return -ETIMEDOUT;
+}
+
+static int ec_wait_obf_set(void)
+{
+ int i;
+
+ for (i = 0; i < EC_TIMEOUT_US; i++) {
+ if (inb(EC_CMD_PORT) & EC_STATUS_OBF)
+ return 0;
+ udelay(EC_POLL_US);
+ }
+ return -ETIMEDOUT;
+}
+
+static int ec_read_reg(u8 reg, u8 *val)
+{
+ int ret;
+
+ ret = ec_wait_ibf_clear();
+ if (ret)
+ return ret;
+
+ outb(EC_CMD_READ, EC_CMD_PORT);
+
+ ret = ec_wait_ibf_clear();
+ if (ret)
+ return ret;
+
+ outb(reg, EC_DATA_PORT);
+
+ ret = ec_wait_obf_set();
+ if (ret)
+ return ret;
+
+ *val = inb(EC_DATA_PORT);
+ return 0;
+}
+
+/* Read a 16-bit big-endian value from two consecutive EC registers. */
+static int ec_read_reg16(u8 reg_hi, u8 reg_lo, u16 *val)
+{
+ int ret;
+ u8 hi, lo;
+
+ ret = ec_read_reg(reg_hi, &hi);
+ if (ret)
+ return ret;
+
+ ret = ec_read_reg(reg_lo, &lo);
+ if (ret)
+ return ret;
+
+ *val = ((u16)hi << 8) | lo;
+ return 0;
+}
+
+static int
+lps_ec_read_string(struct device *dev,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel,
+ const char **str)
+{
+ switch (type) {
+ case hwmon_fan:
+ *str = "CPU Fan";
+ return 0;
+ case hwmon_temp:
+ *str = channel == 0 ? "Board Temp" : "CPU Temp";
+ return 0;
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static umode_t
+lps_ec_is_visible(const void *drvdata,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ switch (type) {
+ case hwmon_fan:
+ if (attr == hwmon_fan_input || attr == hwmon_fan_label)
+ return 0444;
+ break;
+ case hwmon_temp:
+ if (attr == hwmon_temp_input || attr == hwmon_temp_label)
+ return 0444;
+ break;
+ default:
+ break;
+ }
+ return 0;
+}
+
+static int
+lps_ec_read(struct device *dev,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ u16 rpm;
+ u8 v;
+ int ret;
+
+ switch (type) {
+ case hwmon_fan:
+ if (attr != hwmon_fan_input)
+ return -EOPNOTSUPP;
+ ret = ec_read_reg16(EC_REG_FAN_RPM_HI,
+ EC_REG_FAN_RPM_LO, &rpm);
+ if (ret)
+ return ret;
+ *val = rpm;
+ return 0;
+
+ case hwmon_temp:
+ if (attr != hwmon_temp_input)
+ return -EOPNOTSUPP;
+ ret = ec_read_reg(channel == 0 ? EC_REG_TEMP_BOARD
+ : EC_REG_TEMP_CPU,
+ &v);
+ if (ret)
+ return ret;
+ /* EC reports unsigned 8-bit temperature in degrees Celsius */
+ *val = (unsigned long)v * 1000;
+ return 0;
+
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static const struct hwmon_channel_info * const lps_ec_info[] = {
+ HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_LABEL),
+ HWMON_CHANNEL_INFO(temp,
+ HWMON_T_INPUT | HWMON_T_LABEL,
+ HWMON_T_INPUT | HWMON_T_LABEL),
+ NULL
+};
+
+static const struct hwmon_ops lps_ec_ops = {
+ .is_visible = lps_ec_is_visible,
+ .read = lps_ec_read,
+ .read_string = lps_ec_read_string,
+};
+
+static const struct hwmon_chip_info lps_ec_chip_info = {
+ .ops = &lps_ec_ops,
+ .info = lps_ec_info,
+};
+
+static int lps_ec_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device *hwmon;
+ u8 test;
+ int ret;
+
+ /* Sanity check: verify EC is responsive */
+ ret = ec_read_reg(EC_REG_FAN_DUTY, &test);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "EC not responding on ports 0x%x/0x%x\n",
+ EC_DATA_PORT, EC_CMD_PORT);
+
+ hwmon = devm_hwmon_device_register_with_info(dev, DRIVER_NAME, NULL,
+ &lps_ec_chip_info, NULL);
+ if (IS_ERR(hwmon))
+ return dev_err_probe(dev, PTR_ERR(hwmon),
+ "Failed to register hwmon device\n");
+
+ dev_info(dev, "EC hwmon registered (fan duty: %u%%)\n", test);
+ return 0;
+}
+
+/* DMI table with strict BIOS version match (override with force=1) */
+static const struct dmi_system_id lps_ec_dmi_table[] = {
+ {
+ .ident = "LattePanda Sigma",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "LattePanda"),
+ DMI_MATCH(DMI_PRODUCT_NAME, "LattePanda Sigma"),
+ DMI_MATCH(DMI_BIOS_VERSION, "5.27"),
+ },
+ },
+ { } /* terminator */
+};
+MODULE_DEVICE_TABLE(dmi, lps_ec_dmi_table);
+
+/* Loose table (vendor + product only) for use with force=1 */
+static const struct dmi_system_id lps_ec_dmi_table_force[] = {
+ {
+ .ident = "LattePanda Sigma",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "LattePanda"),
+ DMI_MATCH(DMI_PRODUCT_NAME, "LattePanda Sigma"),
+ },
+ },
+ { } /* terminator */
+};
+
+static struct platform_driver lps_ec_driver = {
+ .probe = lps_ec_probe,
+ .driver = {
+ .name = DRIVER_NAME,
+ },
+};
+
+static int __init lps_ec_init(void)
+{
+ int ret;
+
+ if (!dmi_check_system(lps_ec_dmi_table)) {
+ if (!force || !dmi_check_system(lps_ec_dmi_table_force))
+ return -ENODEV;
+ pr_warn("%s: BIOS version not verified, loading due to force=1\n",
+ DRIVER_NAME);
+ }
+
+ ret = platform_driver_register(&lps_ec_driver);
+ if (ret)
+ return ret;
+
+ lps_ec_pdev = platform_device_register_simple(DRIVER_NAME, -1,
+ NULL, 0);
+ if (IS_ERR(lps_ec_pdev)) {
+ platform_driver_unregister(&lps_ec_driver);
+ return PTR_ERR(lps_ec_pdev);
+ }
+
+ return 0;
+}
+
+static void __exit lps_ec_exit(void)
+{
+ platform_device_unregister(lps_ec_pdev);
+ platform_driver_unregister(&lps_ec_driver);
+}
+
+module_init(lps_ec_init);
+module_exit(lps_ec_exit);
+
+MODULE_AUTHOR("Mariano Abad <weimaraner@gmail.com>");
+MODULE_DESCRIPTION("Hardware monitoring driver for LattePanda Sigma EC");
+MODULE_LICENSE("GPL");
--
2.43.0On Mon, Mar 02, 2026 at 03:35:14PM -0300, Mariano Abad wrote:
> The LattePanda Sigma is an x86 single-board computer made by DFRobot,
> featuring an Intel Core i5-1340P and an ITE IT8613E Embedded Controller
> that manages fan speed and thermal monitoring.
>
> The BIOS declares the ACPI Embedded Controller (PNP0C09) with _STA
> returning 0 and provides only stub ECRD/ECWT methods. Since the kernel's
> ACPI EC subsystem never initializes, ec_read() is not available and
> direct port I/O to the standard ACPI EC ports (0x62/0x66) is used. As
> ACPI never accesses the EC, no ACPI Global Lock or namespace mutex is
> required.
>
> The driver exposes:
> - CPU fan speed (RPM, read-only)
> - Board temperature (unsigned 8-bit, degrees Celsius)
> - CPU proximity temperature (unsigned 8-bit, degrees Celsius)
>
> DMI matching restricts the driver to verified LattePanda Sigma hardware
> with BIOS version 5.27. A 'force' module parameter allows loading on
> untested BIOS versions while still requiring vendor/product match.
>
> The EC register map was discovered through firmware reverse engineering
> and confirmed by physical testing.
>
I had trouble to find this patch again and found that you sent it as reply
to the first version.
Documentation/process/submittingpatches.rst explains why you should
never do that.
Anyway, additional feedback:
> +/* Read a 16-bit big-endian value from two consecutive EC registers. */
> +static int ec_read_reg16(u8 reg_hi, u8 reg_lo, u16 *val)
> +{
> + int ret;
> + u8 hi, lo;
> +
> + ret = ec_read_reg(reg_hi, &hi);
> + if (ret)
> + return ret;
> +
> + ret = ec_read_reg(reg_lo, &lo);
> + if (ret)
> + return ret;
> +
> + *val = ((u16)hi << 8) | lo;
> + return 0;
> +}
Is it possible for the 16-bit value (e.g., fan RPM) to roll over between
reading the high and low bytes? Without latching or verifying that the high
byte did not change, reading a rapidly changing 16-bit value as two
independent 8-bit reads can yield a corrupted result (e.g., if it rolls over
from 0x0100 to 0x00FF between reads, producing 0x01FF).
This is AI generated, but it does have a point. lm90 had a similar problem,
which it kind of solved in lm90_read16(). You might want to consider using
a similar approach unless it is guaranteed that this is not a problem.
If so, please add a comment explaining why it is not a problem.
Thanks,
Guenter
On 3/2/26 10:35, Mariano Abad wrote:
> The LattePanda Sigma is an x86 single-board computer made by DFRobot,
> featuring an Intel Core i5-1340P and an ITE IT8613E Embedded Controller
> that manages fan speed and thermal monitoring.
>
> The BIOS declares the ACPI Embedded Controller (PNP0C09) with _STA
> returning 0 and provides only stub ECRD/ECWT methods. Since the kernel's
> ACPI EC subsystem never initializes, ec_read() is not available and
> direct port I/O to the standard ACPI EC ports (0x62/0x66) is used. As
> ACPI never accesses the EC, no ACPI Global Lock or namespace mutex is
> required.
>
> The driver exposes:
> - CPU fan speed (RPM, read-only)
> - Board temperature (unsigned 8-bit, degrees Celsius)
> - CPU proximity temperature (unsigned 8-bit, degrees Celsius)
>
> DMI matching restricts the driver to verified LattePanda Sigma hardware
> with BIOS version 5.27. A 'force' module parameter allows loading on
> untested BIOS versions while still requiring vendor/product match.
>
> The EC register map was discovered through firmware reverse engineering
> and confirmed by physical testing.
>
This should not be part of the commit message.
Couple of additional comments below. Most importantly, there needs to
be some i/o address protection to help ensure that no other driver
accesses to IO port range. Presumably the ec driver should bail out
and not reserve the addresses for itself.
Thanks,
Guenter
> Signed-off-by: Mariano Abad <weimaraner@gmail.com>
> ---
> Changes in v2:
> - Add entry to Documentation/hwmon/index.rst
> - Move reverse engineering notes and ACPI explanation from .rst
> into driver source comments
> - Restrict DMI match to BIOS version 5.27; add 'force' module
> parameter for untested versions
> - Document why no ACPI lock is needed: DSDT analysis shows _STA
> returns 0 and ECRD/ECWT are stubs, so firmware never accesses
> the EC ports
> - Remove driver mutex: the hwmon with_info API already serializes
> all sysfs callbacks
> - Keep udelay() for EC polling: usleep_range() was tested but
> caused EC protocol failures; approach matches the kernel ACPI
> EC driver (drivers/acpi/ec.c)
> - Clarify temperature values are unsigned 8-bit
> - Register platform driver before platform device
> - Link to v1: https://lore.kernel.org/linux-hwmon/20260301023707.1184592-1-weimaraner@gmail.com/
> Documentation/hwmon/index.rst | 1 +
> Documentation/hwmon/lattepanda-sigma-ec.rst | 61 ++++
> MAINTAINERS | 7 +
> drivers/hwmon/Kconfig | 17 +
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/lattepanda-sigma-ec.c | 329 ++++++++++++++++++++
> 6 files changed, 416 insertions(+)
> create mode 100644 Documentation/hwmon/lattepanda-sigma-ec.rst
> create mode 100644 drivers/hwmon/lattepanda-sigma-ec.c
>
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index d91dbb20c..dff283064 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
> kbatt
> kfan
> lan966x
> + lattepanda-sigma-ec
> lineage-pem
> lm25066
> lm63
> diff --git a/Documentation/hwmon/lattepanda-sigma-ec.rst b/Documentation/hwmon/lattepanda-sigma-ec.rst
> new file mode 100644
> index 000000000..8a521ee1f
> --- /dev/null
> +++ b/Documentation/hwmon/lattepanda-sigma-ec.rst
> @@ -0,0 +1,61 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver lattepanda-sigma-ec
> +=================================
> +
> +Supported systems:
> +
> + * LattePanda Sigma (Intel 13th Gen i5-1340P)
> +
> + DMI vendor: LattePanda
> +
> + DMI product: LattePanda Sigma
> +
> + BIOS version: 5.27 (verified)
> +
> + Datasheet: Not available (EC registers discovered empirically)
> +
> +Author: Mariano Abad <weimaraner@gmail.com>
> +
> +Description
> +-----------
> +
> +This driver provides hardware monitoring for the LattePanda Sigma
> +single-board computer made by DFRobot. The board uses an ITE IT8613E
> +Embedded Controller to manage a CPU cooling fan and thermal sensors.
> +
> +The BIOS declares the ACPI Embedded Controller (``PNP0C09``) with
> +``_STA`` returning 0, preventing the kernel's ACPI EC subsystem from
> +initializing. This driver reads the EC directly via the standard ACPI
> +EC I/O ports (``0x62`` data, ``0x66`` command/status).
> +
> +Sysfs attributes
> +----------------
> +
> +======================= ===============================================
> +``fan1_input`` Fan speed in RPM (EC registers 0x2E:0x2F,
> + 16-bit big-endian)
> +``fan1_label`` "CPU Fan"
> +``temp1_input`` Board/ambient temperature in millidegrees
> + Celsius (EC register 0x60, unsigned)
> +``temp1_label`` "Board Temp"
> +``temp2_input`` CPU proximity temperature in millidegrees
> + Celsius (EC register 0x70, unsigned)
> +``temp2_label`` "CPU Temp"
> +======================= ===============================================
> +
> +Module parameters
> +-----------------
> +
> +``force`` (bool, default false)
> + Force loading on BIOS versions other than 5.27. The driver still
> + requires DMI vendor and product name matching.
> +
> +Known limitations
> +-----------------
> +
> +* Fan speed control is not supported. The fan is always under EC
> + automatic control.
> +* The EC register map was verified only on BIOS version 5.27.
> + Other versions may use different register offsets; use the ``force``
> + parameter at your own risk.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 96e97d25e..7b0c5bb5d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14414,6 +14414,13 @@ F: drivers/net/wan/framer/
> F: drivers/pinctrl/pinctrl-pef2256.c
> F: include/linux/framer/
>
> +LATTEPANDA SIGMA EC HARDWARE MONITOR DRIVER
> +M: Mariano Abad <weimaraner@gmail.com>
> +L: linux-hwmon@vger.kernel.org
> +S: Maintained
> +F: Documentation/hwmon/lattepanda-sigma-ec.rst
> +F: drivers/hwmon/lattepanda-sigma-ec.c
> +
> LASI 53c700 driver for PARISC
> M: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> L: linux-scsi@vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 41c381764..f2e2ee96f 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -990,6 +990,23 @@ config SENSORS_LAN966X
> This driver can also be built as a module. If so, the module
> will be called lan966x-hwmon.
>
> +config SENSORS_LATTEPANDA_SIGMA_EC
> + tristate "LattePanda Sigma EC hardware monitoring"
> + depends on X86
> + depends on DMI
> + depends on HAS_IOPORT
> + help
> + If you say yes here you get support for the hardware monitoring
> + features of the Embedded Controller on LattePanda Sigma
> + single-board computers, including CPU fan speed (RPM) and
> + board and CPU temperatures.
> +
> + The driver reads the EC directly via ACPI EC I/O ports and
> + uses DMI matching to ensure it only loads on supported hardware.
> +
> + This driver can also be built as a module. If so, the module
> + will be called lattepanda-sigma-ec.
> +
> config SENSORS_LENOVO_EC
> tristate "Sensor reader for Lenovo ThinkStations"
> depends on X86
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index eade8e3b1..0372fedbb 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -114,6 +114,7 @@ obj-$(CONFIG_SENSORS_K10TEMP) += k10temp.o
> obj-$(CONFIG_SENSORS_KBATT) += kbatt.o
> obj-$(CONFIG_SENSORS_KFAN) += kfan.o
> obj-$(CONFIG_SENSORS_LAN966X) += lan966x-hwmon.o
> +obj-$(CONFIG_SENSORS_LATTEPANDA_SIGMA_EC) += lattepanda-sigma-ec.o
> obj-$(CONFIG_SENSORS_LENOVO_EC) += lenovo-ec-sensors.o
> obj-$(CONFIG_SENSORS_LINEAGE) += lineage-pem.o
> obj-$(CONFIG_SENSORS_LOCHNAGAR) += lochnagar-hwmon.o
> diff --git a/drivers/hwmon/lattepanda-sigma-ec.c b/drivers/hwmon/lattepanda-sigma-ec.c
> new file mode 100644
> index 000000000..2ba51a20d
> --- /dev/null
> +++ b/drivers/hwmon/lattepanda-sigma-ec.c
> @@ -0,0 +1,329 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for LattePanda Sigma EC.
> + *
> + * The LattePanda Sigma is an x86 SBC made by DFRobot with an ITE IT8613E
> + * Embedded Controller that manages a CPU fan and thermal sensors.
> + *
> + * The BIOS declares the ACPI Embedded Controller (PNP0C09) with _STA
> + * returning 0 and provides only stub ECRD/ECWT methods that return Zero
> + * for all registers. Since the kernel's ACPI EC subsystem never initializes,
> + * ec_read() is not available and direct port I/O to the standard ACPI EC
> + * ports (0x62/0x66) is used instead.
> + *
> + * Because ACPI never initializes the EC, there is no concurrent firmware
> + * access to these ports, and no ACPI Global Lock or namespace mutex is
> + * required. The hwmon with_info API serializes all sysfs callbacks,
> + * so no additional driver-level locking is needed.
> + *
If the io space is only used by this driver, it should be reserved,
either with request_muxed_region() while in use or permanently with
request_region() for both the command and data port to ensure that it
is used exclusively by this driver.
> + * The EC register map was discovered by dumping all 256 registers,
> + * identifying those that change in real-time, and validating by physically
> + * stopping the fan and observing the RPM register drop to zero. The map
> + * has been verified on BIOS version 5.27; other versions may differ.
> + *
> + * Copyright (c) 2026 Mariano Abad <weimaraner@gmail.com>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/dmi.h>
> +#include <linux/hwmon.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#define DRIVER_NAME "lattepanda_sigma_ec"
> +
> +/* EC I/O ports (standard ACPI EC interface) */
> +#define EC_DATA_PORT 0x62
> +#define EC_CMD_PORT 0x66 /* also status port */
> +
> +/* EC commands */
> +#define EC_CMD_READ 0x80
> +
> +/* EC status register bits */
> +#define EC_STATUS_OBF 0x01 /* Output Buffer Full */
> +#define EC_STATUS_IBF 0x02 /* Input Buffer Full */
> +
> +/* EC register offsets for LattePanda Sigma (BIOS 5.27) */
> +#define EC_REG_FAN_RPM_HI 0x2E
> +#define EC_REG_FAN_RPM_LO 0x2F
> +#define EC_REG_TEMP_BOARD 0x60
> +#define EC_REG_TEMP_CPU 0x70
> +#define EC_REG_FAN_DUTY 0x93
> +
> +/*
> + * EC polling uses udelay() because the EC typically responds within a
> + * few microseconds. The kernel's own ACPI EC driver (drivers/acpi/ec.c)
> + * likewise uses udelay() for busy-polling with a per-poll delay of 550us.
> + *
> + * usleep_range() was tested but caused EC protocol failures: the EC
> + * clears its status flags within microseconds, and sleeping for 50-100us
> + * between polls allowed the flags to transition past the expected state.
> + *
> + * The worst-case total busy-wait of 25ms covers EC recovery after errors.
> + * In practice the EC responds within 10us so the loop exits immediately.
> + */
> +#define EC_TIMEOUT_US 25000
> +#define EC_POLL_US 1
> +
> +static bool force;
> +module_param(force, bool, 0444);
> +MODULE_PARM_DESC(force,
> + "Force loading on untested BIOS versions (default: false)");
> +
> +static struct platform_device *lps_ec_pdev;
> +
> +static int ec_wait_ibf_clear(void)
> +{
> + int i;
> +
> + for (i = 0; i < EC_TIMEOUT_US; i++) {
> + if (!(inb(EC_CMD_PORT) & EC_STATUS_IBF))
> + return 0;
> + udelay(EC_POLL_US);
> + }
> + return -ETIMEDOUT;
> +}
> +
> +static int ec_wait_obf_set(void)
> +{
> + int i;
> +
> + for (i = 0; i < EC_TIMEOUT_US; i++) {
> + if (inb(EC_CMD_PORT) & EC_STATUS_OBF)
> + return 0;
> + udelay(EC_POLL_US);
> + }
> + return -ETIMEDOUT;
> +}
> +
> +static int ec_read_reg(u8 reg, u8 *val)
> +{
> + int ret;
> +
> + ret = ec_wait_ibf_clear();
> + if (ret)
> + return ret;
> +
> + outb(EC_CMD_READ, EC_CMD_PORT);
> +
> + ret = ec_wait_ibf_clear();
> + if (ret)
> + return ret;
> +
> + outb(reg, EC_DATA_PORT);
> +
> + ret = ec_wait_obf_set();
> + if (ret)
> + return ret;
> +
> + *val = inb(EC_DATA_PORT);
> + return 0;
> +}
> +
> +/* Read a 16-bit big-endian value from two consecutive EC registers. */
> +static int ec_read_reg16(u8 reg_hi, u8 reg_lo, u16 *val)
> +{
> + int ret;
> + u8 hi, lo;
> +
> + ret = ec_read_reg(reg_hi, &hi);
> + if (ret)
> + return ret;
> +
> + ret = ec_read_reg(reg_lo, &lo);
> + if (ret)
> + return ret;
> +
> + *val = ((u16)hi << 8) | lo;
> + return 0;
> +}
> +
> +static int
> +lps_ec_read_string(struct device *dev,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel,
> + const char **str)
> +{
> + switch (type) {
> + case hwmon_fan:
> + *str = "CPU Fan";
> + return 0;
> + case hwmon_temp:
> + *str = channel == 0 ? "Board Temp" : "CPU Temp";
> + return 0;
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> +static umode_t
> +lps_ec_is_visible(const void *drvdata,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel)
> +{
> + switch (type) {
> + case hwmon_fan:
> + if (attr == hwmon_fan_input || attr == hwmon_fan_label)
> + return 0444;
> + break;
> + case hwmon_temp:
> + if (attr == hwmon_temp_input || attr == hwmon_temp_label)
> + return 0444;
> + break;
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> +static int
> +lps_ec_read(struct device *dev,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + u16 rpm;
> + u8 v;
> + int ret;
> +
> + switch (type) {
> + case hwmon_fan:
> + if (attr != hwmon_fan_input)
> + return -EOPNOTSUPP;
> + ret = ec_read_reg16(EC_REG_FAN_RPM_HI,
> + EC_REG_FAN_RPM_LO, &rpm);
> + if (ret)
> + return ret;
> + *val = rpm;
> + return 0;
> +
> + case hwmon_temp:
> + if (attr != hwmon_temp_input)
> + return -EOPNOTSUPP;
> + ret = ec_read_reg(channel == 0 ? EC_REG_TEMP_BOARD
> + : EC_REG_TEMP_CPU,
> + &v);
> + if (ret)
> + return ret;
> + /* EC reports unsigned 8-bit temperature in degrees Celsius */
> + *val = (unsigned long)v * 1000;
> + return 0;
> +
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> +static const struct hwmon_channel_info * const lps_ec_info[] = {
> + HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_LABEL),
> + HWMON_CHANNEL_INFO(temp,
> + HWMON_T_INPUT | HWMON_T_LABEL,
> + HWMON_T_INPUT | HWMON_T_LABEL),
> + NULL
> +};
> +
> +static const struct hwmon_ops lps_ec_ops = {
> + .is_visible = lps_ec_is_visible,
> + .read = lps_ec_read,
> + .read_string = lps_ec_read_string,
> +};
> +
> +static const struct hwmon_chip_info lps_ec_chip_info = {
> + .ops = &lps_ec_ops,
> + .info = lps_ec_info,
> +};
> +
> +static int lps_ec_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device *hwmon;
> + u8 test;
> + int ret;
> +
> + /* Sanity check: verify EC is responsive */
> + ret = ec_read_reg(EC_REG_FAN_DUTY, &test);
> + if (ret)
> + return dev_err_probe(dev, ret,
> + "EC not responding on ports 0x%x/0x%x\n",
> + EC_DATA_PORT, EC_CMD_PORT);
> +
> + hwmon = devm_hwmon_device_register_with_info(dev, DRIVER_NAME, NULL,
> + &lps_ec_chip_info, NULL);
> + if (IS_ERR(hwmon))
> + return dev_err_probe(dev, PTR_ERR(hwmon),
> + "Failed to register hwmon device\n");
> +
> + dev_info(dev, "EC hwmon registered (fan duty: %u%%)\n", test);
> + return 0;
> +}
> +
> +/* DMI table with strict BIOS version match (override with force=1) */
> +static const struct dmi_system_id lps_ec_dmi_table[] = {
> + {
> + .ident = "LattePanda Sigma",
> + .matches = {
> + DMI_MATCH(DMI_SYS_VENDOR, "LattePanda"),
> + DMI_MATCH(DMI_PRODUCT_NAME, "LattePanda Sigma"),
> + DMI_MATCH(DMI_BIOS_VERSION, "5.27"),
> + },
> + },
> + { } /* terminator */
> +};
> +MODULE_DEVICE_TABLE(dmi, lps_ec_dmi_table);
> +
> +/* Loose table (vendor + product only) for use with force=1 */
> +static const struct dmi_system_id lps_ec_dmi_table_force[] = {
> + {
> + .ident = "LattePanda Sigma",
> + .matches = {
> + DMI_MATCH(DMI_SYS_VENDOR, "LattePanda"),
> + DMI_MATCH(DMI_PRODUCT_NAME, "LattePanda Sigma"),
> + },
> + },
> + { } /* terminator */
> +};
> +
> +static struct platform_driver lps_ec_driver = {
> + .probe = lps_ec_probe,
> + .driver = {
> + .name = DRIVER_NAME,
> + },
> +};
> +
> +static int __init lps_ec_init(void)
> +{
> + int ret;
> +
> + if (!dmi_check_system(lps_ec_dmi_table)) {
> + if (!force || !dmi_check_system(lps_ec_dmi_table_force))
> + return -ENODEV;
> + pr_warn("%s: BIOS version not verified, loading due to force=1\n",
> + DRIVER_NAME);
> + }
> +
> + ret = platform_driver_register(&lps_ec_driver);
> + if (ret)
> + return ret;
> +
> + lps_ec_pdev = platform_device_register_simple(DRIVER_NAME, -1,
> + NULL, 0);
CHECK: Alignment should match open parenthesis
#605: FILE: drivers/hwmon/lattepanda-sigma-ec.c:309:
+ lps_ec_pdev = platform_device_register_simple(DRIVER_NAME, -1,
+ NULL, 0);
> + if (IS_ERR(lps_ec_pdev)) {
> + platform_driver_unregister(&lps_ec_driver);
> + return PTR_ERR(lps_ec_pdev);
> + }
> +
> + return 0;
> +}
> +
> +static void __exit lps_ec_exit(void)
> +{
> + platform_device_unregister(lps_ec_pdev);
> + platform_driver_unregister(&lps_ec_driver);
> +}
> +
> +module_init(lps_ec_init);
> +module_exit(lps_ec_exit);
> +
> +MODULE_AUTHOR("Mariano Abad <weimaraner@gmail.com>");
> +MODULE_DESCRIPTION("Hardware monitoring driver for LattePanda Sigma EC");
> +MODULE_LICENSE("GPL");
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