The integration time of the veml6070 depends on an external resistor
(called Rset in the datasheet) and the value configured in the IT
field of the command register, whose supported values are 1/2x, 1x,
2x and 4x.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
---
 drivers/iio/light/veml6070.c | 134 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 126 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/light/veml6070.c b/drivers/iio/light/veml6070.c
index d11ae00f61f8..89b3ccb51515 100644
--- a/drivers/iio/light/veml6070.c
+++ b/drivers/iio/light/veml6070.c
@@ -6,7 +6,7 @@
  *
  * IIO driver for VEML6070 (7-bit I2C slave addresses 0x38 and 0x39)
  *
- * TODO: integration time, ACK signal
+ * TODO: ACK signal
  */
 
 #include <linux/bitfield.h>
@@ -15,6 +15,7 @@
 #include <linux/mutex.h>
 #include <linux/err.h>
 #include <linux/delay.h>
+#include <linux/units.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -29,18 +30,84 @@
 #define VEML6070_COMMAND_RSRVD	BIT(1) /* reserved, set to 1 */
 #define VEML6070_COMMAND_SD	BIT(0) /* shutdown mode when set */
 
-#define VEML6070_IT_10	0x01 /* integration time 1x */
+#define VEML6070_IT_05		0x00
+#define VEML6070_IT_10		0x01
+#define VEML6070_IT_20		0x02
+#define VEML6070_IT_40		0x03
+
+#define VEML6070_MIN_RSET_KOHM	75
+#define VEML6070_MIN_IT_US	15625 /* Rset = 75 kohm, IT = 1/2 */
 
 struct veml6070_data {
 	struct i2c_client *client1;
 	struct i2c_client *client2;
 	u8 config;
 	struct mutex lock;
+	u32 rset;
+	int it[4][2];
 };
 
+static void veml6070_calc_it(struct device *dev, struct veml6070_data *data)
+{
+	int i, tmp_it;
+
+	data->rset = 270000;
+	device_property_read_u32(dev, "rset-ohms", &data->rset);
+
+	if (data->rset < 75000) {
+		dev_warn(dev, "Rset too low, using minimum = 75 kohms\n");
+		data->rset = 75000;
+	}
+
+	if (data->rset > 1200000) {
+		dev_warn(dev, "Rset too high, using maximum = 1200 kohms\n");
+		data->rset = 1200000;
+	}
+
+	/*
+	 * convert to kohm to avoid overflows and work with the same units as
+	 * in the datasheet and simplify UVI operations.
+	 */
+	data->rset /= KILO;
+
+	tmp_it = VEML6070_MIN_IT_US * data->rset / VEML6070_MIN_RSET_KOHM;
+	for (i = 0; i < ARRAY_SIZE(data->it); i++) {
+		data->it[i][0] = (tmp_it << i) / MICRO;
+		data->it[i][1] = (tmp_it << i) % MICRO;
+	}
+}
+
+static int veml6070_get_it(struct veml6070_data *data, int *val, int *val2)
+{
+	int it_idx = FIELD_GET(VEML6070_COMMAND_IT, data->config);
+
+	*val = data->it[it_idx][0];
+	*val2 = data->it[it_idx][1];
+
+	return IIO_VAL_INT_PLUS_MICRO;
+}
+
+static int veml6070_set_it(struct veml6070_data *data, int val, int val2)
+{
+	int it_idx;
+
+	for (it_idx = 0; it_idx < ARRAY_SIZE(data->it); it_idx++) {
+		if (data->it[it_idx][0] == val && data->it[it_idx][1] == val2)
+			break;
+	}
+
+	if (it_idx >= ARRAY_SIZE(data->it))
+		return -EINVAL;
+
+	data->config = (data->config & ~VEML6070_COMMAND_IT) |
+		FIELD_PREP(VEML6070_COMMAND_IT, it_idx);
+
+	return i2c_smbus_write_byte(data->client1, data->config);
+}
+
 static int veml6070_read(struct veml6070_data *data)
 {
-	int ret;
+	int ret, it_ms, val, val2;
 	u8 msb, lsb;
 
 	guard(mutex)(&data->lock);
@@ -51,7 +118,9 @@ static int veml6070_read(struct veml6070_data *data)
 	if (ret < 0)
 		return ret;
 
-	msleep(125 + 10); /* measurement takes up to 125 ms for IT 1x */
+	veml6070_get_it(data, &val, &val2);
+	it_ms = val * MILLI + val2 / (MICRO / MILLI);
+	msleep(it_ms + 10);
 
 	ret = i2c_smbus_read_byte(data->client2); /* read MSB, address 0x39 */
 	if (ret < 0)
@@ -81,26 +150,37 @@ static const struct iio_chan_spec veml6070_channels[] = {
 		.modified = 1,
 		.channel2 = IIO_MOD_LIGHT_UV,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
+		.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),
 	},
 	{
 		.type = IIO_UVINDEX,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
+		.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),
 	}
 };
 
-static int veml6070_to_uv_index(unsigned int val)
+static int veml6070_to_uv_index(struct veml6070_data *data, unsigned int val)
 {
 	/*
 	 * conversion of raw UV intensity values to UV index depends on
 	 * integration time (IT) and value of the resistor connected to
-	 * the RSET pin (default: 270 KOhm)
+	 * the RSET pin.
 	 */
 	unsigned int uvi[11] = {
 		187, 373, 560, /* low */
 		746, 933, 1120, /* moderate */
 		1308, 1494, /* high */
 		1681, 1868, 2054}; /* very high */
-	int i;
+	int i, it_idx;
+
+	it_idx = FIELD_GET(VEML6070_COMMAND_IT, data->config);
+
+	if (!it_idx)
+		val = (val * 270  / data->rset) << 1;
+	else
+		val = (val * 270 / data->rset) >> (it_idx - 1);
 
 	for (i = 0; i < ARRAY_SIZE(uvi); i++)
 		if (val <= uvi[i])
@@ -123,10 +203,44 @@ static int veml6070_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 		if (mask == IIO_CHAN_INFO_PROCESSED)
-			*val = veml6070_to_uv_index(ret);
+			*val = veml6070_to_uv_index(data, ret);
 		else
 			*val = ret;
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_INT_TIME:
+		return veml6070_get_it(data, val, val2);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int veml6070_read_avail(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       const int **vals, int *type, int *length,
+			       long mask)
+{
+	struct veml6070_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_INT_TIME:
+		*vals = (int *)data->it;
+		*length = 2 * ARRAY_SIZE(data->it);
+		*type = IIO_VAL_INT_PLUS_MICRO;
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int veml6070_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	struct veml6070_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_INT_TIME:
+		return veml6070_set_it(data, val, val2);
 	default:
 		return -EINVAL;
 	}
@@ -134,6 +248,8 @@ static int veml6070_read_raw(struct iio_dev *indio_dev,
 
 static const struct iio_info veml6070_info = {
 	.read_raw = veml6070_read_raw,
+	.read_avail  = veml6070_read_avail,
+	.write_raw = veml6070_write_raw,
 };
 
 static void veml6070_i2c_unreg(void *p)
@@ -164,6 +280,8 @@ static int veml6070_probe(struct i2c_client *client)
 	indio_dev->name = VEML6070_DRV_NAME;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	veml6070_calc_it(&client->dev, data);
+
 	ret = devm_regulator_get_enable(&client->dev, "vdd");
 	if (ret < 0)
 		return ret;

-- 
2.43.0

On Mon, 28 Oct 2024 18:14:02 +0100
Javier Carrasco <javier.carrasco.cruz@gmail.com> wrote:

> The integration time of the veml6070 depends on an external resistor
> (called Rset in the datasheet) and the value configured in the IT
> field of the command register, whose supported values are 1/2x, 1x,
> 2x and 4x.
> 
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Minor thing inline about not necessarily papering over wrong
settings in DT.  If someone has a genuine out of range value then we don't
want to carry on with a default. If it is a dt bug then we have no idea
what the correct value is.  Either way I think printing a shouty message
and failing the probe is the way to go.

Jonathan

> ---
>  drivers/iio/light/veml6070.c | 134 ++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 126 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/light/veml6070.c b/drivers/iio/light/veml6070.c
> index d11ae00f61f8..89b3ccb51515 100644
> --- a/drivers/iio/light/veml6070.c
> +++ b/drivers/iio/light/veml6070.c
> @@ -6,7 +6,7 @@
>   *
>   * IIO driver for VEML6070 (7-bit I2C slave addresses 0x38 and 0x39)
>   *
> - * TODO: integration time, ACK signal
> + * TODO: ACK signal
>   */
>  
>  #include <linux/bitfield.h>
> @@ -15,6 +15,7 @@
>  #include <linux/mutex.h>
>  #include <linux/err.h>
>  #include <linux/delay.h>
> +#include <linux/units.h>
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> @@ -29,18 +30,84 @@
>  #define VEML6070_COMMAND_RSRVD	BIT(1) /* reserved, set to 1 */
>  #define VEML6070_COMMAND_SD	BIT(0) /* shutdown mode when set */
>  
> -#define VEML6070_IT_10	0x01 /* integration time 1x */
> +#define VEML6070_IT_05		0x00
> +#define VEML6070_IT_10		0x01
> +#define VEML6070_IT_20		0x02
> +#define VEML6070_IT_40		0x03
> +
> +#define VEML6070_MIN_RSET_KOHM	75
> +#define VEML6070_MIN_IT_US	15625 /* Rset = 75 kohm, IT = 1/2 */
>  
>  struct veml6070_data {
>  	struct i2c_client *client1;
>  	struct i2c_client *client2;
>  	u8 config;
>  	struct mutex lock;
> +	u32 rset;
> +	int it[4][2];
>  };
>  
> +static void veml6070_calc_it(struct device *dev, struct veml6070_data *data)
> +{
> +	int i, tmp_it;
> +
> +	data->rset = 270000;
> +	device_property_read_u32(dev, "rset-ohms", &data->rset);
> +
> +	if (data->rset < 75000) {
> +		dev_warn(dev, "Rset too low, using minimum = 75 kohms\n");
> +		data->rset = 75000;
Why are we papering over a DT issue?  Are there known DT out there that hit this
we want to keep working?

If not I'd just error out on out of range values - that way they get fixed
faster!

> +	}
> +
> +	if (data->rset > 1200000) {
> +		dev_warn(dev, "Rset too high, using maximum = 1200 kohms\n");
> +		data->rset = 1200000;
> +	}
> +
> +	/*
> +	 * convert to kohm to avoid overflows and work with the same units as
> +	 * in the datasheet and simplify UVI operations.
> +	 */
> +	data->rset /= KILO;
> +
> +	tmp_it = VEML6070_MIN_IT_US * data->rset / VEML6070_MIN_RSET_KOHM;
> +	for (i = 0; i < ARRAY_SIZE(data->it); i++) {
> +		data->it[i][0] = (tmp_it << i) / MICRO;
> +		data->it[i][1] = (tmp_it << i) % MICRO;
> +	}
> +}