Message-ID: <20250917-iio-emc1812-v1-2-0b1f74cea7ab@microchip.com>
Date: Wed, 17 Sep 2025 15:21:58 +0300
From: Marius Cristea <marius.cristea@...rochip.com>
To: Jonathan Cameron <jic23@...nel.org>, David Lechner
	<dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, "Andy
 Shevchenko" <andy@...nel.org>, Rob Herring <robh@...nel.org>, "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
CC: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Marius Cristea <marius.cristea@...rochip.com>
Subject: [PATCH 2/2] iio: temperature: add support for EMC1812

This is the iio driver for Microchip EMC1812/13/14/15/33
Multichannel Low-Voltage Remote Diode Sensor Family.

Signed-off-by: Marius Cristea <marius.cristea@...rochip.com>
---
 MAINTAINERS                       |   1 +
 drivers/iio/temperature/Kconfig   |  10 +
 drivers/iio/temperature/Makefile  |   1 +
 drivers/iio/temperature/emc1812.c | 792 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 804 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 09efda36a17e398b3ad807ac47485e530154bae4..15a40cfb7a473789086a1a37459baaff05c97ee2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22867,6 +22867,7 @@ M:	Marius Cristea <marius.cristea@...rochip.com>
 L:	linux-iio@...r.kernel.org
 S:	Supported
 F:	Documentation/devicetree/bindings/iio/temperature/microchip,emc1812.yaml
+F:	drivers/iio/temperature/emc1812.c
 
 SMSC EMC2103 HARDWARE MONITOR DRIVER
 M:	Steve Glendinning <steve.glendinning@...well.net>
diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
index 1244d8e17d504ab23425f0c33f5f2d06dadba663..eb7269bd0a2ab2b6eea777a55c0c520f5e048d53 100644
--- a/drivers/iio/temperature/Kconfig
+++ b/drivers/iio/temperature/Kconfig
@@ -4,6 +4,16 @@
 #
 menu "Temperature sensors"
 
+config EMC1812
+	tristate "Microchip Technology EMC1812 driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Microchip Technology's EMC181X/33
+	  Multichannel Low-Voltage Remote Diode Sensor Family.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called emc1812.
+
 config IQS620AT_TEMP
 	tristate "Azoteq IQS620AT temperature sensor"
 	depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile
index 07d6e65709f7fe6e1ed51867e08112c8a68ee98a..935eafb4d465dcaa3aef61ec26a1b7710a0d140f 100644
--- a/drivers/iio/temperature/Makefile
+++ b/drivers/iio/temperature/Makefile
@@ -3,6 +3,7 @@
 # Makefile for industrial I/O temperature drivers
 #
 
+obj-$(CONFIG_EMC1812) += emc1812.o
 obj-$(CONFIG_IQS620AT_TEMP) += iqs620at-temp.o
 obj-$(CONFIG_LTC2983) += ltc2983.o
 obj-$(CONFIG_HID_SENSOR_TEMP) += hid-sensor-temperature.o
diff --git a/drivers/iio/temperature/emc1812.c b/drivers/iio/temperature/emc1812.c
new file mode 100644
index 0000000000000000000000000000000000000000..b1f567b222026a7138e9c29d739d0240f4dc726f
--- /dev/null
+++ b/drivers/iio/temperature/emc1812.c
@@ -0,0 +1,792 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * IIO driver for Microchip EMC1812/13/14/15/33 Multichannel high-accuracy 2-wire
+ * low-voltage remote diode temperature monitor family.
+ *
+ * Copyright (C) 2025 Microchip Technology Inc. and its subsidiaries
+ *
+ * Author: Marius Cristea <marius.cristea@...rochip.com>
+ *
+ * Datasheet can be found here:
+ * https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/EMC1812-3-4-5-33-Data-Sheet-DS20005751.pdf
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/math64.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/string.h>
+#include <linux/units.h>
+
+/* EMC1812 Registers Addresses */
+#define EMC1812_STATUS_ADDR				0x02
+#define EMC1812_CONFIG_LO_ADDR				0x03
+
+#define EMC1812_CFG_ADDR				0x09
+#define EMC1812_CONV_ADDR				0x0A
+#define EMC1812_INT_DIODE_HIGH_LIMIT_ADDR		0x0B
+#define EMC1812_INT_DIODE_LOW_LIMIT_ADDR		0x0C
+#define EMC1812_EXT1_HIGH_LIMIT_HIGH_BYTE_ADDR		0x0D
+#define EMC1812_EXT1_LOW_LIMIT_HIGH_BYTE_ADDR		0x0E
+#define EMC1812_ONE_SHOT_ADDR				0x0F
+
+#define EMC1812_EXT1_HIGH_LIMIT_LOW_BYTE_ADDR		0x13
+#define EMC1812_EXT1_LOW_LIMIT_LOW_BYTE_ADDR		0x14
+#define EMC1812_EXT2_HIGH_LIMIT_HIGH_BYTE_ADDR		0x15
+#define EMC1812_EXT2_LOW_LIMIT_HIGH_BYTE_ADDR		0x16
+#define EMC1812_EXT2_HIGH_LIMIT_LOW_BYTE_ADDR		0x17
+#define EMC1812_EXT2_LOW_LIMIT_LOW_BYTE_ADDR		0x18
+#define EMC1812_EXT1_THERM_LIMIT_ADDR			0x19
+#define EMC1812_EXT2_THERM_LIMIT_ADDR			0x1A
+#define EMC1812_EXT_DIODE_FAULT_STATUS_ADDR		0x1B
+
+#define EMC1812_DIODE_FAULT_MASK_ADDR			0x1F
+#define EMC1812_INT_DIODE_THERM_LIMIT_ADDR		0x20
+#define EMC1812_THRM_HYS_ADDR				0x21
+#define EMC1812_CONSEC_ALERT_ADDR			0x22
+
+#define EMC1812_EXT1_BETA_CONFIG_ADDR			0x25
+#define EMC1812_EXT2_BETA_CONFIG_ADDR			0x26
+#define EMC1812_EXT1_IDEALITY_FACTOR_ADDR		0x27
+#define EMC1812_EXT2_IDEALITY_FACTOR_ADDR		0x28
+
+#define EMC1812_EXT3_HIGH_LIMIT_HIGH_BYTE_ADDR		0x2C
+#define EMC1812_EXT3_LOW_LIMIT_HIGH_BYTE_ADDR		0x2D
+#define EMC1812_EXT3_HIGH_LIMIT_LOW_BYTE_ADDR		0x2E
+#define EMC1812_EXT3_LOW_LIMIT_LOW_BYTE_ADDR		0x2F
+#define EMC1812_EXT3_THERM_LIMIT_ADDR			0x30
+#define EMC1812_EXT3_IDEALITY_FACTOR_ADDR		0x31
+
+#define EMC1812_EXT4_HIGH_LIMIT_HIGH_BYTE_ADDR		0x34
+#define EMC1812_EXT4_LOW_LIMIT_HIGH_BYTE_ADDR		0x35
+#define EMC1812_EXT4_HIGH_LIMIT_LOW_BYTE_ADDR		0x36
+#define EMC1812_EXT4_LOW_LIMIT_LOW_BYTE_ADDR		0x37
+#define EMC1812_EXT4_THERM_LIMIT_ADDR			0x38
+#define EMC1812_EXT4_IDEALITY_FACTOR_ADDR		0x39
+#define EMC1812_HIGH_LIMIT_STATUS_ADDR			0x3A
+#define EMC1812_LOW_LIMIT_STATUS_ADDR			0x3B
+#define EMC1812_THERM_LIMIT_STATUS_ADDR			0x3C
+#define EMC1812_ROC_GAIN_ADDR				0x3D
+#define EMC1812_ROC_CONFIG_ADDR				0x3E
+#define EMC1812_ROC_STATUS_ADDR				0x3F
+#define EMC1812_R1_RESH_ADDR				0x40
+#define EMC1812_R1_LIMH_ADDR				0x41
+#define EMC1812_R1_LIML_ADDR				0x42
+#define EMC1812_R1_SMPL_ADDR				0x43
+#define EMC1812_R2_RESH_ADDR				0x44
+#define EMC1812_R2_3_RESL_ADDR				0x45
+#define EMC1812_R2_LIMH_ADDR				0x46
+#define EMC1812_R2_LIML_ADDR				0x47
+#define EMC1812_R2_SMPL_ADDR				0x48
+#define EMC1812_PER_MAXTH_1_ADDR			0x49
+#define EMC1812_PER_MAXT1L_ADDR				0x4A
+#define EMC1812_PER_MAXTH_2_ADDR			0x4B
+#define EMC1812_PER_MAXT2_3L_ADDR			0x4C
+#define EMC1812_GBL_MAXT1H_ADDR				0x4D
+#define EMC1812_GBL_MAXT1L_ADDR				0x4E
+#define EMC1812_GBL_MAXT2H_ADDR				0x4F
+#define EMC1812_GBL_MAXT2L_ADDR				0x50
+#define EMC1812_FILTER_SEL_ADDR				0x51
+
+#define EMC1812_INT_HIGH_BYTE_ADDR		0x60
+#define EMC1812_INT_LOW_BYTE_ADDR		0x61
+#define EMC1812_EXT1_HIGH_BYTE_ADDR		0x62
+#define EMC1812_EXT1_LOW_BYTE_ADDR		0x63
+#define EMC1812_EXT2_HIGH_BYTE_ADDR		0x64
+#define EMC1812_EXT2_LOW_BYTE_ADDR		0x65
+#define EMC1812_EXT3_HIGH_BYTE_ADDR		0x66
+#define EMC1812_EXT3_LOW_BYTE_ADDR		0x67
+#define EMC1812_EXT4_HIGH_BYTE_ADDR		0x68
+#define EMC1812_EXT4_LOW_BYTE_ADDR		0x69
+#define EMC1812_HOTTEST_DIODE_HIGH_BYTE_ADDR	0x6A
+#define EMC1812_HOTTEST_DIODE_LOW_BYTE_ADDR	0x6B
+#define EMC1812_HOTTEST_STATUS_ADDR		0x6C
+#define EMC1812_HOTTEST_CFG_ADDR		0x6D
+
+#define EMC1812_PRODUCT_ID_ADDR			0xFD
+#define EMC1812_MANUFACTURER_ID_ADDR		0xFE
+#define EMC1812_REVISION_ADDR			0xFF
+
+/* EMC1812 Config Bits */
+#define EMC1812_CFG_MSKAL			BIT(7)
+#define EMC1812_CFG_RS				BIT(6)
+#define EMC1812_CFG_ATTHM			BIT(5)
+#define EMC1812_CFG_RECD12			BIT(4)
+#define EMC1812_CFG_RECD34			BIT(3)
+#define EMC1812_CFG_RANGE			BIT(2)
+#define EMC1812_CFG_DA_ENA			BIT(1)
+#define EMC1812_CFG_APDD			BIT(0)
+
+/* EMC1812 Status Bits */
+#define EMC1812_STATUS_ROCF			BIT(7)
+#define EMC1812_STATUS_HOTCHG			BIT(6)
+#define EMC1812_STATUS_BUSY			BIT(5)
+#define EMC1812_STATUS_HIGH			BIT(4)
+#define EMC1812_STATUS_LOW			BIT(3)
+#define EMC1812_STATUS_FAULT			BIT(2)
+#define EMC1812_STATUS_ETHRM			BIT(1)
+#define EMC1812_STATUS_ITHRM			BIT(0)
+
+#define EMC1812_BETA_CFG_ADDR(index)		(0x25 + (index))
+
+#define EMC1812_CH_ADDR(index)			(0x60 + 2 * (index))
+
+#define EMC1812_FILTER_MASK_LEN			2
+
+#define EMC1812_PID				0x81
+#define EMC1813_PID				0x87
+#define EMC1814_PID				0x84
+#define EMC1815_PID				0x85
+#define EMC1833_PID				0x83
+
+/* The maximum number of channels a member of the family can have */
+#define EMC1812_MAX_NUM_CHANNELS		5
+#define EMC1812_TEMP_OFFSET			-64
+
+#define EMC1812_CHAN(index, si, __address) ({						\
+	(struct iio_chan_spec) {                                                        \
+		.type = IIO_TEMP,							\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),				\
+		.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ) |	\
+		BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),			\
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ) |		\
+		BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY) |			\
+		BIT(IIO_CHAN_INFO_OFFSET) |						\
+		BIT(IIO_CHAN_INFO_SCALE),						\
+		.channel = index,							\
+		.address = __address,							\
+		.scan_index = si,							\
+		.scan_type = {								\
+			.sign = 'u',							\
+			.realbits = 8,							\
+			.storagebits = 8,						\
+		},									\
+		.indexed = 1,								\
+	};										\
+})
+
+/**
+ * struct emc1812_features - features of a emc1812 instance
+ * @name:		chip's name
+ * @phys_channels:	number of physical channels supported by the chip
+ * @lock_beta1:		lock beta compensation on channel 1 when APDD is enabled
+ * @lock_beta2:		lock beta compensation on channel 2 when APDD is enabled
+ * @allow_apdd		whether the chip supports enabling APDD
+ */
+struct emc1812_features {
+	const char	*name;
+	u8		phys_channels;
+	bool		lock_beta1;
+	bool		lock_beta2;
+};
+
+static const struct emc1812_features emc1833_chip_config = {
+	.name = "emc1833",
+	.phys_channels = 3,
+	.lock_beta1 = true,
+	.lock_beta2 = false,
+};
+
+static const struct emc1812_features emc1812_chip_config = {
+	.name = "emc1812",
+	.phys_channels = 2,
+	.lock_beta1 = false,
+	.lock_beta2 = false,
+};
+
+static const struct emc1812_features emc1813_chip_config = {
+	.name = "emc1813",
+	.phys_channels = 3,
+	.lock_beta1 = false,
+	.lock_beta2 = false,
+};
+
+static const struct emc1812_features emc1814_chip_config = {
+	.name = "emc1814",
+	.phys_channels = 4,
+	.lock_beta1 = false,
+	.lock_beta2 = true,
+};
+
+static const struct emc1812_features emc1815_chip_config = {
+	.name = "emc1815",
+	.phys_channels = 5,
+	.lock_beta1 = true,
+	.lock_beta2 = true,
+};
+
+static const unsigned int emc1812_freq[][2] = {
+	{  0,  62500 },
+	{  0, 125000 },
+	{  0, 250000 },
+	{  0, 500000 },
+	{  1,      0 },
+	{  2,      0 },
+	{  4,      0 },
+	{  8,      0 },
+	{ 16,      0 },
+	{ 32,      0 },
+	{ 64,      0 },
+};
+
+/*
+ * For moving average filter with window size 4 and 8, constants were calculated
+ * using: F(@-3db) = Sampling_Frequency(Hz) / (Window_Size * 2)
+ * In case the moving average filter is disabled we will print the sampling frequency.
+ */
+static const unsigned int emc1812_3db_values_map_tbl[11][3][2] = {
+	{ {  0,  62500 }, { 0,   7813 }, { 0,   3906 }, },
+	{ {  0, 125000 }, { 0,  15625 }, { 0,   7813 }, },
+	{ {  0, 250000 }, { 0,  31250 }, { 0,  15625 }, },
+	{ {  0, 500000 }, { 0,  62500 }, { 0,  31250 }, },
+	{ {  1,      0 }, { 0, 125000 }, { 0,  62500 }, },
+	{ {  2,      0 }, { 0, 250000 }, { 0, 125000 }, },
+	{ {  4,      0 }, { 0, 500000 }, { 0, 250000 }, },
+	{ {  8,      0 }, { 1,      0 }, { 0, 500000 }, },
+	{ { 16,      0 }, { 2,      0 }, { 1,      0 }, },
+	{ { 32,      0 }, { 4,      0 }, { 2,      0 }, },
+	{ { 64,      0 }, { 8,      0 }, { 4,      0 }, },
+};
+
+static const unsigned int emc1812_window_size[3] = { 1, 4, 8 };
+
+/**
+ * struct emc1812_priv - information about chip parameters
+ * @labels:		labels of the channels
+ * @chip:		pointer to structure holding chip features
+ * @ideality_value:	ideality factor value for each external channel
+ * @iio_chan:		specifications for each channel
+ * @beta_values:	beta compensation value for external channel 1 and 2
+ * @freq_idx:		index representing the current sampling frequency
+ * @regmap:		device register map
+ * @recd34_en:		state of Resistance Error Correction (REC) on channels 3 and 4
+ * @recd12_en:		state of Resistance Error Correction (REC) on channels 1 and 2
+ * @lock:		synchronize access to driver's state members
+ * @apdd_en:		state of anti-parallel diode mode
+ * @num_channels:	number of active physical channels
+ */
+struct emc1812_priv {
+	const char *labels[EMC1812_MAX_NUM_CHANNELS];
+	const struct emc1812_features *chip;
+	unsigned int ideality_value[4];
+	struct iio_chan_spec iio_chan[EMC1812_MAX_NUM_CHANNELS];
+	unsigned int beta_values[2];
+	unsigned int freq_idx;
+	struct regmap *regmap;
+	bool recd34_en;
+	bool recd12_en;
+	struct mutex lock;	 /* Synchronize access to driver's state members */
+	bool apdd_en;
+	u8 num_channels;
+};
+
+/* emc1812 regmap configuration */
+static const struct regmap_range emc1812_regmap_writable_ranges[] = {
+	regmap_reg_range(EMC1812_CFG_ADDR, EMC1812_ONE_SHOT_ADDR),
+	regmap_reg_range(EMC1812_EXT1_HIGH_LIMIT_LOW_BYTE_ADDR,
+			 EMC1812_EXT_DIODE_FAULT_STATUS_ADDR),
+	regmap_reg_range(EMC1812_DIODE_FAULT_MASK_ADDR, EMC1812_CONSEC_ALERT_ADDR),
+	regmap_reg_range(EMC1812_EXT1_BETA_CONFIG_ADDR, EMC1812_FILTER_SEL_ADDR),
+	regmap_reg_range(EMC1812_HOTTEST_STATUS_ADDR, EMC1812_HOTTEST_CFG_ADDR),
+};
+
+static const struct regmap_access_table emc1812_regmap_wr_table = {
+	.yes_ranges = emc1812_regmap_writable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(emc1812_regmap_writable_ranges),
+};
+
+static const struct regmap_range emc1812_regmap_rd_ranges[] = {
+	regmap_reg_range(EMC1812_STATUS_ADDR, EMC1812_CONFIG_LO_ADDR),
+	regmap_reg_range(EMC1812_CFG_ADDR, EMC1812_ONE_SHOT_ADDR),
+	regmap_reg_range(EMC1812_EXT1_HIGH_LIMIT_LOW_BYTE_ADDR,
+			 EMC1812_EXT_DIODE_FAULT_STATUS_ADDR),
+	regmap_reg_range(EMC1812_DIODE_FAULT_MASK_ADDR, EMC1812_CONSEC_ALERT_ADDR),
+	regmap_reg_range(EMC1812_EXT1_BETA_CONFIG_ADDR, EMC1812_FILTER_SEL_ADDR),
+	regmap_reg_range(EMC1812_INT_HIGH_BYTE_ADDR, EMC1812_HOTTEST_CFG_ADDR),
+	regmap_reg_range(EMC1812_PRODUCT_ID_ADDR, EMC1812_REVISION_ADDR),
+};
+
+static const struct regmap_access_table emc1812_regmap_rd_table = {
+	.yes_ranges = emc1812_regmap_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(emc1812_regmap_rd_ranges),
+};
+
+static bool emc1812_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case EMC1812_STATUS_ADDR:
+	case EMC1812_EXT_DIODE_FAULT_STATUS_ADDR:
+	case EMC1812_DIODE_FAULT_MASK_ADDR:
+
+	case EMC1812_EXT1_BETA_CONFIG_ADDR:
+	case EMC1812_EXT2_BETA_CONFIG_ADDR:
+
+	case EMC1812_HIGH_LIMIT_STATUS_ADDR:
+	case EMC1812_LOW_LIMIT_STATUS_ADDR:
+	case EMC1812_THERM_LIMIT_STATUS_ADDR:
+	case EMC1812_ROC_STATUS_ADDR:
+	case EMC1812_PER_MAXTH_1_ADDR:
+	case EMC1812_PER_MAXT1L_ADDR:
+	case EMC1812_PER_MAXTH_2_ADDR:
+	case EMC1812_PER_MAXT2_3L_ADDR:
+	case EMC1812_GBL_MAXT1H_ADDR:
+	case EMC1812_GBL_MAXT1L_ADDR:
+	case EMC1812_GBL_MAXT2H_ADDR:
+	case EMC1812_GBL_MAXT2L_ADDR:
+	case EMC1812_INT_HIGH_BYTE_ADDR:
+	case EMC1812_INT_LOW_BYTE_ADDR:
+	case EMC1812_EXT1_HIGH_BYTE_ADDR:
+	case EMC1812_EXT1_LOW_BYTE_ADDR:
+	case EMC1812_EXT2_HIGH_BYTE_ADDR:
+	case EMC1812_EXT2_LOW_BYTE_ADDR:
+	case EMC1812_EXT3_HIGH_BYTE_ADDR:
+	case EMC1812_EXT3_LOW_BYTE_ADDR:
+	case EMC1812_EXT4_HIGH_BYTE_ADDR:
+	case EMC1812_EXT4_LOW_BYTE_ADDR:
+	case EMC1812_HOTTEST_DIODE_HIGH_BYTE_ADDR:
+	case EMC1812_HOTTEST_DIODE_LOW_BYTE_ADDR:
+	case EMC1812_HOTTEST_STATUS_ADDR:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config emc1812_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.rd_table = &emc1812_regmap_rd_table,
+	.wr_table = &emc1812_regmap_wr_table,
+	.volatile_reg = emc1812_is_volatile_reg,
+	.max_register = EMC1812_REVISION_ADDR,
+};
+
+static int emc1812_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			      const int **vals, int *type, int *length, long mask)
+{
+	struct emc1812_priv *priv = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*vals = emc1812_freq[0];
+		*length = ARRAY_SIZE(emc1812_freq) * 2;
+		*type = IIO_VAL_INT_PLUS_MICRO;
+		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		*vals = emc1812_3db_values_map_tbl[priv->freq_idx][0];
+		*length = ARRAY_SIZE(emc1812_3db_values_map_tbl[priv->freq_idx]) * 2;
+		*type = IIO_VAL_INT_PLUS_MICRO;
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int emc1812_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct emc1812_priv *priv = iio_priv(indio_dev);
+	unsigned int idx, tmp_reg;
+	__be16 tmp_be16;
+	int ret;
+
+	guard(mutex)(&priv->lock);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = regmap_bulk_read(priv->regmap, EMC1812_CH_ADDR(chan->channel),
+				       &tmp_be16, sizeof(tmp_be16));
+		if (ret)
+			return ret;
+
+		*val = be16_to_cpu(tmp_be16);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = 3906250;
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = emc1812_freq[priv->freq_idx][0];
+		*val2 = emc1812_freq[priv->freq_idx][1];
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		ret = regmap_read(priv->regmap, EMC1812_FILTER_SEL_ADDR, &tmp_reg);
+		if (ret)
+			return ret;
+
+		idx = hweight32(tmp_reg);
+		*val = emc1812_3db_values_map_tbl[priv->freq_idx][idx][0];
+		*val2 = emc1812_3db_values_map_tbl[priv->freq_idx][idx][1];
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OFFSET:
+		*val = EMC1812_TEMP_OFFSET;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int emc1812_read_label(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan, char *label)
+{
+	struct emc1812_priv *priv = iio_priv(indio_dev);
+
+	if (chan->channel >= EMC1812_MAX_NUM_CHANNELS)
+		return -EINVAL;
+
+	return sysfs_emit(label, "%s\n", priv->labels[chan->channel]);
+}
+
+static int emc1812_write_raw_get_fmt(struct iio_dev *indio_dev,
+				     struct iio_chan_spec const *chan, long info)
+{
+	switch (info) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int emc1812_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	struct emc1812_priv *priv = iio_priv(indio_dev);
+	unsigned int i;
+	int ret;
+
+	guard(mutex)(&priv->lock);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		for (i = 0; i < ARRAY_SIZE(emc1812_freq); i++)
+			if (val == emc1812_freq[i][0] && val2 == emc1812_freq[i][1])
+				break;
+
+		if (i == ARRAY_SIZE(emc1812_freq))
+			return -EINVAL;
+
+		ret = regmap_write(priv->regmap, EMC1812_CONV_ADDR, i);
+		if (ret)
+			return ret;
+
+		priv->freq_idx = i;
+		break;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		for (i = 0; i < ARRAY_SIZE(emc1812_3db_values_map_tbl[priv->freq_idx]); i++)
+			if (val == emc1812_3db_values_map_tbl[priv->freq_idx][i][0] &&
+			    val2 == emc1812_3db_values_map_tbl[priv->freq_idx][i][1])
+				break;
+
+		if (i == ARRAY_SIZE(emc1812_3db_values_map_tbl[priv->freq_idx]))
+			return -EINVAL;
+
+		/*
+		 * In emc1812_3db_values_map_tbl the second index maps:
+		 * 0 for filter off
+		 * 1 for filter at level 1
+		 * 2 for filter at level 2
+		 */
+		if (i == 2)
+			i = 3;
+
+		ret = regmap_write(priv->regmap, EMC1812_FILTER_SEL_ADDR, i);
+		if (ret)
+			return ret;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct iio_info emc1812_info = {
+	.read_raw = emc1812_read_raw,
+	.read_label = emc1812_read_label,
+	.read_avail = emc1812_read_avail,
+	.write_raw_get_fmt = emc1812_write_raw_get_fmt,
+	.write_raw = emc1812_write_raw,
+};
+
+static int emc1812_init(struct emc1812_priv *priv)
+{
+	unsigned int i;
+	int ret;
+	u8 val;
+
+	/*
+	 * Depending on the chip, lock channel beta 1 and/or 2 to Diode Mode
+	 * when APDD is enabled.
+	 */
+	if (priv->chip->lock_beta1 && priv->apdd_en)
+		priv->beta_values[0] = 0x0F;
+	if (priv->chip->lock_beta2 && priv->apdd_en)
+		priv->beta_values[1] = 0x0F;
+
+	/*
+	 * Set default values in registers. APDD, RECD12 and RECD34 are active
+	 * on 0.
+	 * Set the device to be in Run (Active) state and converting on all
+	 * channels.
+	 * The temperature measurement range is -64°C to +191.875°C.
+	 */
+	val = FIELD_PREP(EMC1812_CFG_MSKAL, 1) |
+	      FIELD_PREP(EMC1812_CFG_RS, 0) |
+	      FIELD_PREP(EMC1812_CFG_ATTHM, 1) |
+	      FIELD_PREP(EMC1812_CFG_RECD12, !priv->recd12_en) |
+	      FIELD_PREP(EMC1812_CFG_RECD34, !priv->recd34_en) |
+	      FIELD_PREP(EMC1812_CFG_RANGE, 1) |
+	      FIELD_PREP(EMC1812_CFG_DA_ENA, 0) |
+	      FIELD_PREP(EMC1812_CFG_APDD, !priv->apdd_en);
+
+	ret = regmap_write(priv->regmap, EMC1812_CFG_ADDR, val);
+	if (ret)
+		return ret;
+
+	/* Default is 4 conversions/seconds */
+	ret = regmap_write(priv->regmap, EMC1812_CONV_ADDR, 6);
+	if (ret)
+		return ret;
+	priv->freq_idx = 6;
+
+	ret = regmap_write(priv->regmap, EMC1812_THRM_HYS_ADDR, 0x0A);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_CONSEC_ALERT_ADDR, 0x70);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_FILTER_SEL_ADDR, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_HOTTEST_CFG_ADDR, 0);
+	if (ret)
+		return ret;
+
+	/* Set beta1 and beta2 compensation parameters */
+	for (i = 0; i < ARRAY_SIZE(priv->beta_values); i++) {
+		ret = regmap_write(priv->regmap, EMC1812_BETA_CFG_ADDR(i),
+				   priv->beta_values[i]);
+		if (ret)
+			return ret;
+	}
+
+	/* Set ideality factor for all external channels */
+	ret = regmap_write(priv->regmap, EMC1812_EXT1_IDEALITY_FACTOR_ADDR,
+			   priv->ideality_value[0]);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_EXT2_IDEALITY_FACTOR_ADDR,
+			   priv->ideality_value[1]);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_EXT3_IDEALITY_FACTOR_ADDR,
+			   priv->ideality_value[2]);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, EMC1812_EXT4_IDEALITY_FACTOR_ADDR,
+			   priv->ideality_value[3]);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int emc1812_parse_fw_config(struct emc1812_priv *priv, struct device *dev,
+				   int device_nr_channels)
+{
+	unsigned int reg_nr, iio_idx, tmp;
+	int ret;
+
+	priv->apdd_en = device_property_read_bool(dev, "microchip,enable-anti-parallel");
+	priv->recd12_en = device_property_read_bool(dev, "microchip,parasitic-res-on-channel1-2");
+	priv->recd34_en = device_property_read_bool(dev, "microchip,parasitic-res-on-channel3-4");
+
+	memset32(priv->beta_values, 16, ARRAY_SIZE(priv->beta_values));
+	device_property_read_u32(dev, "microchip,beta1", &priv->beta_values[0]);
+	device_property_read_u32(dev, "microchip,beta2", &priv->beta_values[1]);
+	if (priv->beta_values[0] > 16 || priv->beta_values[1] > 16)
+		return dev_err_probe(dev, -EINVAL, "Invalid beta value\n");
+
+	priv->num_channels = device_get_child_node_count(dev) + 1;
+
+	if (priv->num_channels > priv->chip->phys_channels)
+		return dev_err_probe(dev, -E2BIG, "More channels than the chip supports\n");
+
+	priv->iio_chan[0] = EMC1812_CHAN(0, 0, EMC1812_CH_ADDR(0));
+
+	priv->labels[0] = "internal_diode";
+	iio_idx = 1;
+	device_for_each_child_node_scoped(dev, child) {
+		ret = fwnode_property_read_u32(child, "reg", &reg_nr);
+		if (ret || reg_nr >= priv->chip->phys_channels)
+			return dev_err_probe(dev, -EINVAL,
+				     "The index of the channels does not match the chip\n");
+
+		ret = fwnode_property_read_u32(child, "microchip,ideality-factor", &tmp);
+		if (ret == 0) {
+			if (tmp < 8  || tmp > 63)
+				return dev_err_probe(dev, ret, "Invalid ideality value\n");
+			priv->ideality_value[reg_nr - 1] = tmp;
+		} else {
+			priv->ideality_value[reg_nr - 1] = 18;
+		}
+
+		fwnode_property_read_string(child, "label", &priv->labels[reg_nr]);
+
+		priv->iio_chan[iio_idx++] = EMC1812_CHAN(reg_nr, reg_nr, EMC1812_CH_ADDR(reg_nr));
+	}
+
+	return 0;
+}
+
+static int emc1812_chip_identify(struct emc1812_priv *priv, struct i2c_client *client)
+{
+	int ret, tmp;
+
+	ret = regmap_read(priv->regmap, EMC1812_PRODUCT_ID_ADDR, &tmp);
+	if (ret)
+		return ret;
+
+	switch (tmp) {
+	case EMC1812_PID:
+		priv->chip = &emc1812_chip_config;
+		break;
+	case EMC1813_PID:
+		priv->chip = &emc1813_chip_config;
+		break;
+	case EMC1814_PID:
+		priv->chip = &emc1814_chip_config;
+		break;
+	case EMC1815_PID:
+		priv->chip = &emc1815_chip_config;
+		break;
+	case EMC1833_PID:
+		priv->chip = &emc1833_chip_config;
+		break;
+	default:
+		/*
+		 * If failed to identify the hardware based on internal registers,
+		 * try using fallback compatible in device tree to deal with some
+		 * newer part number.
+		 */
+		priv->chip = i2c_get_match_data(client);
+		if (!priv->chip)
+			return -EINVAL;
+		break;
+	}
+	return 0;
+}
+
+static int emc1812_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct emc1812_priv *priv;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(indio_dev);
+	priv->regmap = devm_regmap_init_i2c(client, &emc1812_regmap_config);
+	if (IS_ERR(priv->regmap))
+		return dev_err_probe(dev, PTR_ERR(priv->regmap),
+				     "Cannot initialize register map\n");
+
+	ret = devm_mutex_init(dev, &priv->lock);
+	if (ret)
+		return ret;
+
+	ret = emc1812_chip_identify(priv, client);
+	if (ret)
+		return dev_err_probe(dev, ret, "Chip identification fails\n");
+
+	dev_info(dev, "Device name: %s\n", priv->chip->name);
+
+	ret = emc1812_parse_fw_config(priv, dev, priv->chip->phys_channels);
+	if (ret)
+		return ret;
+
+	ret = emc1812_init(priv);
+	if (ret)
+		return dev_err_probe(dev, ret, "Cannot initialize device\n");
+
+	indio_dev->name = priv->chip->name;
+	indio_dev->info = &emc1812_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = &priv->iio_chan[0];
+	indio_dev->num_channels = priv->num_channels;
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Cannot register IIO device\n");
+
+	return 0;
+}
+
+static const struct i2c_device_id emc1812_id[] = {
+	{ .name = "emc1812", .driver_data = (kernel_ulong_t)&emc1812_chip_config },
+	{ .name = "emc1813", .driver_data = (kernel_ulong_t)&emc1813_chip_config },
+	{ .name = "emc1814", .driver_data = (kernel_ulong_t)&emc1814_chip_config },
+	{ .name = "emc1815", .driver_data = (kernel_ulong_t)&emc1815_chip_config },
+	{ .name = "emc1833", .driver_data = (kernel_ulong_t)&emc1833_chip_config },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, emc1812_id);
+
+static const struct of_device_id emc1812_of_match[] = {
+	{
+		.compatible = "microchip,emc1812",
+		.data = &emc1812_chip_config
+	},
+	{
+		.compatible = "microchip,emc1813",
+		.data = &emc1813_chip_config
+	},
+	{
+		.compatible = "microchip,emc1814",
+		.data = &emc1814_chip_config
+	},
+	{
+		.compatible = "microchip,emc1815",
+		.data = &emc1815_chip_config
+	},
+	{
+		.compatible = "microchip,emc1833",
+		.data = &emc1833_chip_config
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, emc1812_of_match);
+
+static struct i2c_driver emc1812_driver = {
+	.driver	 = {
+		.name = "emc1812",
+		.of_match_table = emc1812_of_match,
+	},
+	.probe = emc1812_probe,
+	.id_table = emc1812_id,
+};
+module_i2c_driver(emc1812_driver);
+
+MODULE_AUTHOR("Marius Cristea <marius.cristea@...rochip.com>");
+MODULE_DESCRIPTION("EMC1812/13/14/15/33 high-accuracy remote diode temperature monitor Driver");
+MODULE_LICENSE("GPL");

-- 
2.48.1

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