[PATCH v3 0/2] iio: light: veml6070: add integration time

[PATCH v3 0/2] iio: light: veml6070: add integration time

[Javier Carrasco]

This series adds a missing feature in the veml6070 driver to select the
integration time, which also depends on an external restistor that has
been added to the corresponding bindings.

The datasheet provides a Refresh time vs Rset graph (figure 7), which
does not clearly specify the minimum and maximum values for Rset. The
manufacuter has confirmed that no values under 75 kohms should be used
to keep linearity, and the graph does not go beyond 1200 kohms, which is
also the biggest Rset used in the application note. The default value of
270 kohms is the one currently used in the driver to calculate the UVI.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
---
Changes in v3:
- veml6075.yaml: simplify property handling (describe it completely at
  the top and add block for the devices that do not support it).
- veml6070.c: use int instead of u32 for the integration times.
- veml6070.c: refactor default rset value assignment.
- veml6070.c: drop comment about default Rset and IT.
- veml6070.c: use units from units.h
- Link to v2: https://lore.kernel.org/r/20241024-veml6070-integration-time-v2-0-d53272ec0feb@gmail.com

Changes in v2:
- Rebase onto iio/testing and drop applied patches.
- veml6075.yaml: use documented -ohms, top-level definition and
  per-device restriction.
- veml6075.yaml: add default value.
- veml6075.yaml: fix typo in commit message.
- veml6070.c: adjust rset property name and convert from ohms to kohms
  to avoid overflows and work with the same units as in the datasheet.
- veml6070.c: change default to 270 kohms (already used as default
  value to calculate UVI).
- veml6070.c: calculate UVI according to the current integration time.
- veml6070.c: re-calculate measurement time (i.e. msleep()) with the
  current integration time.
- Link to v1: https://lore.kernel.org/r/20241017-veml6070-integration-time-v1-0-3507d17d562a@gmail.com

---
Javier Carrasco (2):
      dt-bindings: iio: light: veml6075: document rset-ohms
      iio: light: veml6070: add support for integration time

 .../bindings/iio/light/vishay,veml6075.yaml        |  18 +++
 drivers/iio/light/veml6070.c                       | 134 +++++++++++++++++++--
 2 files changed, 144 insertions(+), 8 deletions(-)
---
base-commit: 9090ececac9ff1e22fb7e042f3c886990a8fb090
change-id: 20241014-veml6070-integration-time-78daf4eaad2f

Best regards,
-- 
Javier Carrasco <javier.carrasco.cruz@gmail.com>

[PATCH v3 1/2] dt-bindings: iio: light: veml6075: document rset-ohms

[Javier Carrasco]

The veml6070 provides a configurable integration time by means of an
external resistor (Rset in the datasheet) with values between 75 and
1200 kohms.

Document rset-ohms to select the integration time.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
---
 .../devicetree/bindings/iio/light/vishay,veml6075.yaml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
index 96c1317541fa..5381a90f7f7e 100644
--- a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
+++ b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
@@ -22,6 +22,13 @@ properties:
   reg:
     maxItems: 1
 
+  rset-ohms:
+    description:
+      Resistor used to select the integration time.
+    default: 270000
+    minimum: 75000
+    maximum: 1200000
+
   vdd-supply: true
 
 required:
@@ -29,6 +36,17 @@ required:
   - reg
   - vdd-supply
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          enum:
+            - vishay,veml6040
+            - vishay,veml6075
+    then:
+      properties:
+        rset-ohms: false
+
 additionalProperties: false
 
 examples:

-- 
2.43.0

[PATCH v3 2/2] iio: light: veml6070: add support for integration time

[Javier Carrasco]

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

Re: [PATCH v3 1/2] dt-bindings: iio: light: veml6075: document rset-ohms

[Krzysztof Kozlowski]

On Mon, Oct 28, 2024 at 06:14:01PM +0100, Javier Carrasco wrote:
> The veml6070 provides a configurable integration time by means of an
> external resistor (Rset in the datasheet) with values between 75 and
> 1200 kohms.
> 
> Document rset-ohms to select the integration time.
> 
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
> ---
>  .../devicetree/bindings/iio/light/vishay,veml6075.yaml | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
> index 96c1317541fa..5381a90f7f7e 100644
> --- a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
> +++ b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
> @@ -22,6 +22,13 @@ properties:
>    reg:
>      maxItems: 1
>  
> +  rset-ohms:

I missed last time this, sorry:
This looks specific to this device, so missing vendor prefix. Otherwise
you should use an existing property or make it a generic, IIO property
in common schema.

Best regards,
Krzysztof

Re: [PATCH v3 1/2] dt-bindings: iio: light: veml6075: document rset-ohms

[Javier Carrasco]

On 29/10/2024 08:33, Krzysztof Kozlowski wrote:
> On Mon, Oct 28, 2024 at 06:14:01PM +0100, Javier Carrasco wrote:
>> The veml6070 provides a configurable integration time by means of an
>> external resistor (Rset in the datasheet) with values between 75 and
>> 1200 kohms.
>>
>> Document rset-ohms to select the integration time.
>>
>> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
>> ---
>>  .../devicetree/bindings/iio/light/vishay,veml6075.yaml | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
>> index 96c1317541fa..5381a90f7f7e 100644
>> --- a/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
>> +++ b/Documentation/devicetree/bindings/iio/light/vishay,veml6075.yaml
>> @@ -22,6 +22,13 @@ properties:
>>    reg:
>>      maxItems: 1
>>  
>> +  rset-ohms:
> 
> I missed last time this, sorry:
> This looks specific to this device, so missing vendor prefix. Otherwise
> you should use an existing property or make it a generic, IIO property
> in common schema.
> 
> Best regards,
> Krzysztof
> 

This is a device-specific property, so I will rename to

vishay,reset-ohms

Thanks and best regards,
Javier Carrasco

Re: [PATCH v3 2/2] iio: light: veml6070: add support for integration time

[Jonathan Cameron]

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;
> +	}
> +}