drivers/hwmon/lattepanda-sigma-ec.c - third_party/linux - Git at Google

 // 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/ioport.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.
  *
  * The EC may update the register pair between reading the high and low
  * bytes, which could produce a corrupted value if the high byte rolls
  * over (e.g., 0x0100 -> 0x00FF read as 0x01FF). Guard against this by
  * re-reading the high byte after reading the low byte. If the high byte
  * changed, re-read the low byte to get a consistent pair.
  * See also lm90_read16() which uses the same approach.
  */
 static int ec_read_reg16(u8 reg_hi, u8 reg_lo, u16 *val)
 {
 	int ret;
 	u8 oldh, newh, lo;

 	ret = ec_read_reg(reg_hi, &oldh);
 	if (ret)
 		return ret;

 	ret = ec_read_reg(reg_lo, &lo);
 	if (ret)
 		return ret;

 	ret = ec_read_reg(reg_hi, &newh);
 	if (ret)
 		return ret;

 	if (oldh != newh) {
 		ret = ec_read_reg(reg_lo, &lo);
 		if (ret)
 			return ret;
 	}

 	*val = ((u16)newh << 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;

 	if (!devm_request_region(dev, EC_DATA_PORT, 1, DRIVER_NAME))
 		return dev_err_probe(dev, -EBUSY,
 				     "Failed to request EC data port 0x%x\n",
 				     EC_DATA_PORT);

 	if (!devm_request_region(dev, EC_CMD_PORT, 1, DRIVER_NAME))
 		return dev_err_probe(dev, -EBUSY,
 				     "Failed to request EC cmd port 0x%x\n",
 				     EC_CMD_PORT);

 	/* 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");
	// 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/ioport.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.
	*
	* The EC may update the register pair between reading the high and low
	* bytes, which could produce a corrupted value if the high byte rolls
	* over (e.g., 0x0100 -> 0x00FF read as 0x01FF). Guard against this by
	* re-reading the high byte after reading the low byte. If the high byte
	* changed, re-read the low byte to get a consistent pair.
	* See also lm90_read16() which uses the same approach.
	*/
	static int ec_read_reg16(u8 reg_hi, u8 reg_lo, u16 *val)
	{
	int ret;
	u8 oldh, newh, lo;

	ret = ec_read_reg(reg_hi, &oldh);
	if (ret)
	return ret;

	ret = ec_read_reg(reg_lo, &lo);
	if (ret)
	return ret;

	ret = ec_read_reg(reg_hi, &newh);
	if (ret)
	return ret;

	if (oldh != newh) {
	ret = ec_read_reg(reg_lo, &lo);
	if (ret)
	return ret;
	}

	*val = ((u16)newh << 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;

	if (!devm_request_region(dev, EC_DATA_PORT, 1, DRIVER_NAME))
	return dev_err_probe(dev, -EBUSY,
	"Failed to request EC data port 0x%x\n",
	EC_DATA_PORT);

	if (!devm_request_region(dev, EC_CMD_PORT, 1, DRIVER_NAME))
	return dev_err_probe(dev, -EBUSY,
	"Failed to request EC cmd port 0x%x\n",
	EC_CMD_PORT);

	/* 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");