hwmon: (pmbus/ltc2978) add support for lt717x

Add support for LT7170 and LT7171. The LT7170 and LT7171 are 20 A, 16 V,
Single- or Dual-Phase, Silent Switcher Step-Down Regulators with Digital
Power System Management.

The relevant registers in the LT7170 and LT7171 are similar to those in
the LTC3887, but with fewer channels. This adds the chip ID and
identification of ASCII to differentiate between the LT7170 and LT7171.
These devices support polling for status updates and clearing peak
values. The data format for voltage, current, and temperature is set to
IEEE754 for precision and compatibility.

Co-developed-by: Cherrence Sarip <[e-mail]>
Signed-off-by: Cherrence Sarip <[e-mail]>
Signed-off-by: Kim Seer Paller <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/pmbus/Kconfig

···
 	depends on SENSORS_LTC2978 && REGULATOR
 	help
 	  If you say yes here you get regulator support for Linear Technology
-	  LTC3880, LTC3883, LTC3884, LTC3886, LTC3887, LTC3889, LTC7841,
-	  LTC7880, LTM4644, LTM4673, LTM4675, LTM4676, LTM4677, LTM4678,
-	  LTM4680, LTM4686, and LTM4700.
+	  LT7170, LT7171, LTC3880, LTC3883, LTC3884, LTC3886, LTC3887, LTC3889,
+	  LTC7841, LTC7880, LTM4644, LTM4673, LTM4675, LTM4676, LTM4677,
+	  LTM4678, LTM4680, LTM4686, and LTM4700.
 
 config SENSORS_LTC3815
 	tristate "Linear Technologies LTC3815"

drivers/hwmon/pmbus/ltc2978.c

···
 	/* Managers */
 	ltc2972, ltc2974, ltc2975, ltc2977, ltc2978, ltc2979, ltc2980,
 	/* Controllers */
-	ltc3880, ltc3882, ltc3883, ltc3884, ltc3886, ltc3887, ltc3889, ltc7132,
-	ltc7841, ltc7880,
+	lt7170, lt7171, ltc3880, ltc3882, ltc3883, ltc3884, ltc3886, ltc3887,
+	ltc3889, ltc7132, ltc7841, ltc7880,
 	/* Modules */
 	ltm2987, ltm4664, ltm4673, ltm4675, ltm4676, ltm4677, ltm4678, ltm4680,
 	ltm4686, ltm4700,
···
 
 #define LTC2978_ID_MASK			0xfff0
 
+#define LT7170_ID			0x1C10
 #define LTC2972_ID			0x0310
 #define LTC2974_ID			0x0210
 #define LTC2975_ID			0x0220
···
 }
 
 static const struct i2c_device_id ltc2978_id[] = {
+	{"lt7170", lt7170},
+	{"lt7171", lt7171},
 	{"ltc2972", ltc2972},
 	{"ltc2974", ltc2974},
 	{"ltc2975", ltc2975},
···
 		ret = i2c_smbus_read_block_data(client, PMBUS_MFR_ID, buf);
 		if (ret < 0)
 			return ret;
-		if (ret < 3 || strncmp(buf, "LTC", 3))
+		if (ret < 3 || (strncmp(buf, "LTC", 3) && strncmp(buf, "ADI", 3)))
 			return -ENODEV;
 
 		ret = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
···
 	}
 
 	chip_id &= LTC2978_ID_MASK;
+
+	if (chip_id == LT7170_ID) {
+		u8 buf[I2C_SMBUS_BLOCK_MAX];
+		int ret;
+
+		ret = i2c_smbus_read_i2c_block_data(client, PMBUS_IC_DEVICE_ID,
+						    sizeof(buf), buf);
+		if (ret < 0)
+			return ret;
+
+		if (!strncmp(buf + 1, "LT7170", 6) ||
+		    !strncmp(buf + 1, "LT7170-1", 8))
+			return lt7170;
+		if (!strncmp(buf + 1, "LT7171", 6) ||
+		    !strncmp(buf + 1, "LT7171-1", 8))
+			return lt7171;
+
+		return -ENODEV;
+	}
 
 	if (chip_id == LTC2972_ID)
 		return ltc2972;
···
 	data->temp2_max = 0x7c00;
 
 	switch (data->id) {
+	case lt7170:
+	case lt7171:
+		data->features |= FEAT_CLEAR_PEAKS | FEAT_NEEDS_POLLING;
+		info->read_word_data = ltc3883_read_word_data;
+		info->pages = LTC3883_NUM_PAGES;
+		info->format[PSC_VOLTAGE_IN] = ieee754;
+		info->format[PSC_VOLTAGE_OUT] = ieee754;
+		info->format[PSC_CURRENT_OUT] = ieee754;
+		info->format[PSC_TEMPERATURE] = ieee754;
+		info->func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
+		  | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
+		  | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT
+		  | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP;
+		break;
 	case ltc2972:
 		info->read_word_data = ltc2975_read_word_data;
 		info->pages = LTC2972_NUM_PAGES;
···
 
 #ifdef CONFIG_OF
 static const struct of_device_id ltc2978_of_match[] = {
+	{ .compatible = "lltc,lt7170" },
+	{ .compatible = "lltc,lt7171" },
 	{ .compatible = "lltc,ltc2972" },
 	{ .compatible = "lltc,ltc2974" },
 	{ .compatible = "lltc,ltc2975" },