iio: chemical: vz89x: add support for VZ89TE part

Add support the VZ89TE variant which removes the voc_short channel,
and has CRC check for data transactions.
Signed-off-by: NMatt Ranostay <mranostay@gmail.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/chemical/vz89x.c

@@ -34,8 +34,17 @@
 #define VZ89X_VOC_TVOC_IDX		2
 #define VZ89X_VOC_RESISTANCE_IDX	3
 
+#define VZ89TE_REG_MEASUREMENT		0x0c
+#define VZ89TE_REG_MEASUREMENT_RD_SIZE	7
+#define VZ89TE_REG_MEASUREMENT_WR_SIZE	6
+
+#define VZ89TE_VOC_TVOC_IDX		0
+#define VZ89TE_VOC_CO2_IDX		1
+#define VZ89TE_VOC_RESISTANCE_IDX	2
+
 enum {
 	VZ89X,
+	VZ89TE,
 };
 
 struct vz89x_chip_data;
@@ -47,7 +56,7 @@ struct vz89x_data {
 	int (*xfer)(struct vz89x_data *data, u8 cmd);
 
 	unsigned long last_update;
-	u8 buffer[VZ89X_REG_MEASUREMENT_RD_SIZE];
+	u8 buffer[VZ89TE_REG_MEASUREMENT_RD_SIZE];
 };
 
 struct vz89x_chip_data {
@@ -90,6 +99,40 @@ static const struct iio_chan_spec vz89x_channels[] = {
 		.info_mask_separate =
 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 		.address = VZ89X_VOC_RESISTANCE_IDX,
+		.scan_index = -1,
+		.scan_type = {
+			.endianness = IIO_LE,
+		},
+	},
+};
+
+static const struct iio_chan_spec vz89te_channels[] = {
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_VOC,
+		.modified = 1,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
+		.address = VZ89TE_VOC_TVOC_IDX,
+	},
+
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_CO2,
+		.modified = 1,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
+		.address = VZ89TE_VOC_CO2_IDX,
+	},
+	{
+		.type = IIO_RESISTANCE,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.address = VZ89TE_VOC_RESISTANCE_IDX,
+		.scan_index = -1,
+		.scan_type = {
+			.endianness = IIO_BE,
+		},
 	},
 };
 
@@ -121,13 +164,28 @@ static bool vz89x_measurement_is_valid(struct vz89x_data *data)
 	return !!(data->buffer[data->chip->read_size - 1] > 0);
 }
 
+/* VZ89TE device has a modified CRC-8 two complement check */
+static bool vz89te_measurement_is_valid(struct vz89x_data *data)
+{
+	u8 crc = 0;
+	int i, sum = 0;
+
+	for (i = 0; i < (data->chip->read_size - 1); i++) {
+		sum = crc + data->buffer[i];
+		crc = sum;
+		crc += sum / 256;
+	}
+
+	return !((0xff - crc) == data->buffer[data->chip->read_size - 1]);
+}
+
 static int vz89x_i2c_xfer(struct vz89x_data *data, u8 cmd)
 {
 	const struct vz89x_chip_data *chip = data->chip;
 	struct i2c_client *client = data->client;
 	struct i2c_msg msg[2];
 	int ret;
-	u8 buf[3] = { cmd, 0, 0};
+	u8 buf[6] = { cmd, 0, 0, 0, 0, 0xf3 };
 
 	msg[0].addr = client->addr;
 	msg[0].flags = client->flags;
@@ -186,11 +244,24 @@ static int vz89x_get_measurement(struct vz89x_data *data)
 	return 0;
 }
 
-static int vz89x_get_resistance_reading(struct vz89x_data *data)
+static int vz89x_get_resistance_reading(struct vz89x_data *data,
+					struct iio_chan_spec const *chan,
+					int *val)
 {
-	u8 *buf = &data->buffer[VZ89X_VOC_RESISTANCE_IDX];
+	u8 *tmp = (u8 *) &data->buffer[chan->address];
 
-	return buf[0] | (buf[1] << 8);
+	switch (chan->scan_type.endianness) {
+	case IIO_LE:
+		*val = le32_to_cpup((__le32 *) tmp) & GENMASK(23, 0);
+		break;
+	case IIO_BE:
+		*val = be32_to_cpup((__be32 *) tmp) >> 8;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 static int vz89x_read_raw(struct iio_dev *indio_dev,
@@ -209,15 +280,15 @@ static int vz89x_read_raw(struct iio_dev *indio_dev,
 		if (ret)
 			return ret;
 
-		switch (chan->address) {
-		case VZ89X_VOC_CO2_IDX:
-		case VZ89X_VOC_SHORT_IDX:
-		case VZ89X_VOC_TVOC_IDX:
+		switch (chan->type) {
+		case IIO_CONCENTRATION:
 			*val = data->buffer[chan->address];
 			return IIO_VAL_INT;
-		case VZ89X_VOC_RESISTANCE_IDX:
-			*val = vz89x_get_resistance_reading(data);
-			return IIO_VAL_INT;
+		case IIO_RESISTANCE:
+			ret = vz89x_get_resistance_reading(data, chan, val);
+			if (!ret)
+				return IIO_VAL_INT;
+			break;
 		default:
 			return -EINVAL;
 		}
@@ -232,12 +303,12 @@ static int vz89x_read_raw(struct iio_dev *indio_dev,
 		}
 		break;
 	case IIO_CHAN_INFO_OFFSET:
-		switch (chan->address) {
-		case VZ89X_VOC_CO2_IDX:
+		switch (chan->channel2) {
+		case IIO_MOD_CO2:
 			*val = 44;
 			*val2 = 250000;
 			return IIO_VAL_INT_PLUS_MICRO;
-		case VZ89X_VOC_TVOC_IDX:
+		case IIO_MOD_VOC:
 			*val = -13;
 			return IIO_VAL_INT;
 		default:
@@ -265,10 +336,21 @@ static const struct vz89x_chip_data vz89x_chips[] = {
 		.channels = vz89x_channels,
 		.num_channels = ARRAY_SIZE(vz89x_channels),
 	},
+	{
+		.valid = vz89te_measurement_is_valid,
+
+		.cmd = VZ89TE_REG_MEASUREMENT,
+		.read_size = VZ89TE_REG_MEASUREMENT_RD_SIZE,
+		.write_size = VZ89TE_REG_MEASUREMENT_WR_SIZE,
+
+		.channels = vz89te_channels,
+		.num_channels = ARRAY_SIZE(vz89te_channels),
+	},
 };
 
 static const struct of_device_id vz89x_dt_ids[] = {
 	{ .compatible = "sgx,vz89x", .data = (void *) VZ89X },
+	{ .compatible = "sgx,vz89te", .data = (void *) VZ89TE },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, vz89x_dt_ids);
@@ -319,6 +401,7 @@ static int vz89x_probe(struct i2c_client *client,
 
 static const struct i2c_device_id vz89x_id[] = {
 	{ "vz89x", VZ89X },
+	{ "vz89te", VZ89TE },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, vz89x_id);