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Mon, 02 Mar 2026 10:35:19 -0800 (PST) From: Mariano Abad To: linux-hwmon@vger.kernel.org Cc: linux@roeck-us.net, corbet@lwn.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Mariano Abad Subject: [PATCH v2] hwmon: Add LattePanda Sigma EC driver Date: Mon, 2 Mar 2026 15:35:14 -0300 Message-ID: <20260302183514.3021503-1-weimaraner@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260301023707.1184592-1-weimaraner@gmail.com> References: <20260301023707.1184592-1-weimaraner@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- 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/hw= mon/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 +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D + +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 + +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 +---------------- + +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +``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" +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +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/ =20 +LATTEPANDA SIGMA EC HARDWARE MONITOR DRIVER +M: Mariano Abad +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" 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. =20 +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-$(CONFIG_SENSORS_K10TEMP) +=3D k10temp.o obj-$(CONFIG_SENSORS_KBATT) +=3D kbatt.o obj-$(CONFIG_SENSORS_KFAN) +=3D kfan.o obj-$(CONFIG_SENSORS_LAN966X) +=3D lan966x-hwmon.o +obj-$(CONFIG_SENSORS_LATTEPANDA_SIGMA_EC) +=3D lattepanda-sigma-ec.o obj-$(CONFIG_SENSORS_LENOVO_EC) +=3D lenovo-ec-sensors.o obj-$(CONFIG_SENSORS_LINEAGE) +=3D lineage-pem.o obj-$(CONFIG_SENSORS_LOCHNAGAR) +=3D 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 initializ= es, + * 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 + */ + +#include +#include +#include +#include +#include +#include + +#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 =3D 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 =3D 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 =3D ec_wait_ibf_clear(); + if (ret) + return ret; + + outb(EC_CMD_READ, EC_CMD_PORT); + + ret =3D ec_wait_ibf_clear(); + if (ret) + return ret; + + outb(reg, EC_DATA_PORT); + + ret =3D ec_wait_obf_set(); + if (ret) + return ret; + + *val =3D 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 =3D ec_read_reg(reg_hi, &hi); + if (ret) + return ret; + + ret =3D ec_read_reg(reg_lo, &lo); + if (ret) + return ret; + + *val =3D ((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 =3D "CPU Fan"; + return 0; + case hwmon_temp: + *str =3D channel =3D=3D 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 =3D=3D hwmon_fan_input || attr =3D=3D hwmon_fan_label) + return 0444; + break; + case hwmon_temp: + if (attr =3D=3D hwmon_temp_input || attr =3D=3D 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 !=3D hwmon_fan_input) + return -EOPNOTSUPP; + ret =3D ec_read_reg16(EC_REG_FAN_RPM_HI, + EC_REG_FAN_RPM_LO, &rpm); + if (ret) + return ret; + *val =3D rpm; + return 0; + + case hwmon_temp: + if (attr !=3D hwmon_temp_input) + return -EOPNOTSUPP; + ret =3D ec_read_reg(channel =3D=3D 0 ? EC_REG_TEMP_BOARD + : EC_REG_TEMP_CPU, + &v); + if (ret) + return ret; + /* EC reports unsigned 8-bit temperature in degrees Celsius */ + *val =3D (unsigned long)v * 1000; + return 0; + + default: + return -EOPNOTSUPP; + } +} + +static const struct hwmon_channel_info * const lps_ec_info[] =3D { + 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 =3D { + .is_visible =3D lps_ec_is_visible, + .read =3D lps_ec_read, + .read_string =3D lps_ec_read_string, +}; + +static const struct hwmon_chip_info lps_ec_chip_info =3D { + .ops =3D &lps_ec_ops, + .info =3D lps_ec_info, +}; + +static int lps_ec_probe(struct platform_device *pdev) +{ + struct device *dev =3D &pdev->dev; + struct device *hwmon; + u8 test; + int ret; + + /* Sanity check: verify EC is responsive */ + ret =3D 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 =3D 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=3D1) */ +static const struct dmi_system_id lps_ec_dmi_table[] =3D { + { + .ident =3D "LattePanda Sigma", + .matches =3D { + 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=3D1 */ +static const struct dmi_system_id lps_ec_dmi_table_force[] =3D { + { + .ident =3D "LattePanda Sigma", + .matches =3D { + DMI_MATCH(DMI_SYS_VENDOR, "LattePanda"), + DMI_MATCH(DMI_PRODUCT_NAME, "LattePanda Sigma"), + }, + }, + { } /* terminator */ +}; + +static struct platform_driver lps_ec_driver =3D { + .probe =3D lps_ec_probe, + .driver =3D { + .name =3D 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=3D1\n", + DRIVER_NAME); + } + + ret =3D platform_driver_register(&lps_ec_driver); + if (ret) + return ret; + + lps_ec_pdev =3D 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 "); +MODULE_DESCRIPTION("Hardware monitoring driver for LattePanda Sigma EC"); +MODULE_LICENSE("GPL"); --=20 2.43.0