[PATCH v2 0/4] iio: accel: adxl345: add calibration offset and sampling frequency support

[PATCH v2 0/4] iio: accel: adxl345: add calibration offset and sampling frequency support

[Akinobu Mita]

This patchset adds calibration offset and sampling frequency support for
adxl345 driver with some preparatory changes.

* v2
- Adjust the value for the calibbias to make the same scale as the _raw
  measurement, and remove misused calibscale.

Akinobu Mita (4):
  iio: accel: adxl345: add link to datasheet
  iio: accel: adxl345: use scan_index for accessing accel registers
  iio: accel: adxl345: add calibration offset support
  iio: accel: adxl345: add sampling frequency support

 drivers/iio/accel/adxl345_core.c | 123 +++++++++++++++++++++++++++++++++++----
 1 file changed, 112 insertions(+), 11 deletions(-)

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
-- 
2.7.4

[PATCH v2 1/4] iio: accel: adxl345: add link to datasheet

[Akinobu Mita]

Add a link to the ADXL345 datasheet

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
* v2
- No changes from v1

 drivers/iio/accel/adxl345_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 7251d0e..8e0d56b 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -6,6 +6,8 @@
  * This file is subject to the terms and conditions of version 2 of
  * the GNU General Public License. See the file COPYING in the main
  * directory of this archive for more details.
+ *
+ * Datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf
  */
 
 #include <linux/module.h>
-- 
2.7.4

[PATCH v2 2/4] iio: accel: adxl345: use scan_index for accessing accel registers

[Akinobu Mita]

Currently the address field in iio_chan_spec is filled with an accel
data register address for the corresponding axis.

In preparation for adding calibration offset support, this makes use of
scan_index field to access accel data registers instead of using address
field.  This change makes it easier to access both accel registers and
calibration offset registers with fewer lines of code as these are
located in X-axis, Y-axis, Z-axis order.

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
* v2
- No changes from v1

 drivers/iio/accel/adxl345_core.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 8e0d56b..6b62f82 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -49,19 +49,19 @@ struct adxl345_data {
 	u8 data_range;
 };
 
-#define ADXL345_CHANNEL(reg, axis) {					\
+#define ADXL345_CHANNEL(si, axis) {					\
 	.type = IIO_ACCEL,						\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##axis,					\
-	.address = reg,							\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.scan_index = si,						\
 }
 
 static const struct iio_chan_spec adxl345_channels[] = {
-	ADXL345_CHANNEL(ADXL345_REG_DATAX0, X),
-	ADXL345_CHANNEL(ADXL345_REG_DATAY0, Y),
-	ADXL345_CHANNEL(ADXL345_REG_DATAZ0, Z),
+	ADXL345_CHANNEL(0, X),
+	ADXL345_CHANNEL(1, Y),
+	ADXL345_CHANNEL(2, Z),
 };
 
 static int adxl345_read_raw(struct iio_dev *indio_dev,
@@ -79,8 +79,9 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 		 * ADXL345_REG_DATA(X0/Y0/Z0) contain the least significant byte
 		 * and ADXL345_REG_DATA(X0/Y0/Z0) + 1 the most significant byte
 		 */
-		ret = regmap_bulk_read(data->regmap, chan->address, &regval,
-				       sizeof(regval));
+		ret = regmap_bulk_read(data->regmap, ADXL345_REG_DATAX0 +
+				       sizeof(regval) * chan->scan_index,
+				       &regval, sizeof(regval));
 		if (ret < 0)
 			return ret;
 
-- 
2.7.4

Re: [PATCH v2 2/4] iio: accel: adxl345: use scan_index for accessing accel registers

[Andy Shevchenko]

On Mon, Jun 18, 2018 at 6:59 PM, Akinobu Mita <akinobu.mita@gmail.com> wrote:
> Currently the address field in iio_chan_spec is filled with an accel
> data register address for the corresponding axis.
>
> In preparation for adding calibration offset support, this makes use of
> scan_index field to access accel data registers instead of using address
> field.  This change makes it easier to access both accel registers and
> calibration offset registers with fewer lines of code as these are
> located in X-axis, Y-axis, Z-axis order.

> +               ret = regmap_bulk_read(data->regmap, ADXL345_REG_DATAX0 +
> +                                      sizeof(regval) * chan->scan_index,
> +                                      &regval, sizeof(regval));

Can't we do something like

#define ADXL345_REG_DATA_AXIS(si)  (0x32 + (si) * sizeof(__le16))

instead and use where applicable?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/4] iio: accel: adxl345: use scan_index for accessing accel registers

[Jonathan Cameron]

On Tue, 19 Jun 2018 00:59:10 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> Currently the address field in iio_chan_spec is filled with an accel
> data register address for the corresponding axis.
> 
> In preparation for adding calibration offset support, this makes use of
> scan_index field to access accel data registers instead of using address
> field.  This change makes it easier to access both accel registers and
> calibration offset registers with fewer lines of code as these are
> located in X-axis, Y-axis, Z-axis order.
> 
Hmm. My issue here is that scan_index exists for a very specific purpose
and that purpose is only relevant once we have buffered support (where
it describes the ordering in the binary data from the chrdev).

I'd rather we stuck to using the addr field, just changed it to an
index like you are doing here.

It's possible a later adding of buffered support would not work with these
particular scan_index values.

Jonathan

> Cc: Eva Rachel Retuya <eraretuya@gmail.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> ---
> * v2
> - No changes from v1
> 
>  drivers/iio/accel/adxl345_core.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 8e0d56b..6b62f82 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -49,19 +49,19 @@ struct adxl345_data {
>  	u8 data_range;
>  };
>  
> -#define ADXL345_CHANNEL(reg, axis) {					\
> +#define ADXL345_CHANNEL(si, axis) {					\
>  	.type = IIO_ACCEL,						\
>  	.modified = 1,							\
>  	.channel2 = IIO_MOD_##axis,					\
> -	.address = reg,							\
>  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
>  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
> +	.scan_index = si,						\
>  }
>  
>  static const struct iio_chan_spec adxl345_channels[] = {
> -	ADXL345_CHANNEL(ADXL345_REG_DATAX0, X),
> -	ADXL345_CHANNEL(ADXL345_REG_DATAY0, Y),
> -	ADXL345_CHANNEL(ADXL345_REG_DATAZ0, Z),
> +	ADXL345_CHANNEL(0, X),
> +	ADXL345_CHANNEL(1, Y),
> +	ADXL345_CHANNEL(2, Z),
>  };
>  
>  static int adxl345_read_raw(struct iio_dev *indio_dev,
> @@ -79,8 +79,9 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
>  		 * ADXL345_REG_DATA(X0/Y0/Z0) contain the least significant byte
>  		 * and ADXL345_REG_DATA(X0/Y0/Z0) + 1 the most significant byte
>  		 */
> -		ret = regmap_bulk_read(data->regmap, chan->address, &regval,
> -				       sizeof(regval));
> +		ret = regmap_bulk_read(data->regmap, ADXL345_REG_DATAX0 +
> +				       sizeof(regval) * chan->scan_index,
> +				       &regval, sizeof(regval));
>  		if (ret < 0)
>  			return ret;
>  

[PATCH v2 3/4] iio: accel: adxl345: add calibration offset support

[Akinobu Mita]

The ADXL345 provides the offset adjustment registers for each axis.
This adds the iio channel information for the calibraion offsets with
that feature.

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
* v2
- Adjust the value for the calibbias to make the same scale as the _raw
  measurement, and remove misused calibscale.

 drivers/iio/accel/adxl345_core.c | 47 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 6b62f82..a6cdf1b 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -18,6 +18,9 @@
 #include "adxl345.h"
 
 #define ADXL345_REG_DEVID		0x00
+#define ADXL345_REG_OFSX		0x1e
+#define ADXL345_REG_OFSY		0x1f
+#define ADXL345_REG_OFSZ		0x20
 #define ADXL345_REG_POWER_CTL		0x2D
 #define ADXL345_REG_DATA_FORMAT		0x31
 #define ADXL345_REG_DATAX0		0x32
@@ -53,7 +56,8 @@ struct adxl345_data {
 	.type = IIO_ACCEL,						\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##axis,					\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+		BIT(IIO_CHAN_INFO_CALIBBIAS),				\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
 	.scan_index = si,						\
 }
@@ -69,7 +73,8 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 			    int *val, int *val2, long mask)
 {
 	struct adxl345_data *data = iio_priv(indio_dev);
-	__le16 regval;
+	__le16 accel;
+	unsigned int regval;
 	int ret;
 
 	switch (mask) {
@@ -80,18 +85,49 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 		 * and ADXL345_REG_DATA(X0/Y0/Z0) + 1 the most significant byte
 		 */
 		ret = regmap_bulk_read(data->regmap, ADXL345_REG_DATAX0 +
-				       sizeof(regval) * chan->scan_index,
-				       &regval, sizeof(regval));
+				       sizeof(accel) * chan->scan_index, &accel,
+				       sizeof(accel));
 		if (ret < 0)
 			return ret;
 
-		*val = sign_extend32(le16_to_cpu(regval), 12);
+		*val = sign_extend32(le16_to_cpu(accel), 12);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 0;
 		*val2 = adxl345_uscale;
 
 		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		ret = regmap_read(data->regmap,
+				  ADXL345_REG_OFSX + chan->scan_index, &regval);
+		if (ret < 0)
+			return ret;
+		/*
+		 * 8-bit resolution at +/- 2g, that is 4x accel data scale
+		 * factor
+		 */
+		*val = sign_extend32(regval, 7) * 4;
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static int adxl345_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	struct adxl345_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_CALIBBIAS:
+		/*
+		 * 8-bit resolution at +/- 2g, that is 4x accel data scale
+		 * factor
+		 */
+		return regmap_write(data->regmap,
+				    ADXL345_REG_OFSX + chan->scan_index,
+				    val / 4);
 	}
 
 	return -EINVAL;
@@ -99,6 +135,7 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 
 static const struct iio_info adxl345_info = {
 	.read_raw	= adxl345_read_raw,
+	.write_raw	= adxl345_write_raw,
 };
 
 int adxl345_core_probe(struct device *dev, struct regmap *regmap,
-- 
2.7.4

Re: [PATCH v2 3/4] iio: accel: adxl345: add calibration offset support

[Andy Shevchenko]

On Mon, Jun 18, 2018 at 6:59 PM, Akinobu Mita <akinobu.mita@gmail.com> wrote:
> The ADXL345 provides the offset adjustment registers for each axis.
> This adds the iio channel information for the calibraion offsets with
> that feature.

>  #define ADXL345_REG_DEVID              0x00
> +#define ADXL345_REG_OFSX               0x1e
> +#define ADXL345_REG_OFSY               0x1f
> +#define ADXL345_REG_OFSZ               0x20

+ #define ADXL345_REG_OSF_AXIS(si) (0x1e + (si))

> -       __le16 regval;
> +       __le16 accel;

I would rather split renamint to a separate change.

>                 ret = regmap_bulk_read(data->regmap, ADXL345_REG_DATAX0 +
> -                                      sizeof(regval) * chan->scan_index,
> -                                      &regval, sizeof(regval));
> +                                      sizeof(accel) * chan->scan_index, &accel,
> +                                      sizeof(accel));

This hunk would be cleaner after addressing my proposal for patch 2.

> +       case IIO_CHAN_INFO_CALIBBIAS:
> +               ret = regmap_read(data->regmap,
> +                                 ADXL345_REG_OFSX + chan->scan_index, &regval);

So, for my opinion an axis agnostic macro would suit better above and here.

> +               return regmap_write(data->regmap,
> +                                   ADXL345_REG_OFSX + chan->scan_index,
> +                                   val / 4);

Ditto.

-- 
With Best Regards,
Andy Shevchenko

[PATCH v2 4/4] iio: accel: adxl345: add sampling frequency support

[Akinobu Mita]

The ADXL345 provides selectable output data rate.  This adds the iio
channel information for the sampling frequency with that feature.

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
* v2
- No changes from v1

 drivers/iio/accel/adxl345_core.c | 63 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index a6cdf1b..25cbaa5 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -14,6 +14,7 @@
 #include <linux/regmap.h>
 
 #include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
 
 #include "adxl345.h"
 
@@ -21,12 +22,15 @@
 #define ADXL345_REG_OFSX		0x1e
 #define ADXL345_REG_OFSY		0x1f
 #define ADXL345_REG_OFSZ		0x20
+#define ADXL345_REG_BW_RATE		0x2C
 #define ADXL345_REG_POWER_CTL		0x2D
 #define ADXL345_REG_DATA_FORMAT		0x31
 #define ADXL345_REG_DATAX0		0x32
 #define ADXL345_REG_DATAY0		0x34
 #define ADXL345_REG_DATAZ0		0x36
 
+#define ADXL345_BW_RATE			GENMASK(3, 0)
+
 #define ADXL345_POWER_CTL_MEASURE	BIT(3)
 #define ADXL345_POWER_CTL_STANDBY	0x00
 
@@ -58,7 +62,8 @@ struct adxl345_data {
 	.channel2 = IIO_MOD_##axis,					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
 		BIT(IIO_CHAN_INFO_CALIBBIAS),				\
-	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
+		BIT(IIO_CHAN_INFO_SAMP_FREQ),				\
 	.scan_index = si,						\
 }
 
@@ -68,6 +73,28 @@ static const struct iio_chan_spec adxl345_channels[] = {
 	ADXL345_CHANNEL(2, Z),
 };
 
+static const struct {
+	int val;
+	int val2;
+} adxl345_samp_freq_table[] = {
+	{ 0, 97656 },
+	{ 0, 195313 },
+	{ 0, 390625 },
+	{ 0, 781250 },
+	{ 1, 562500 },
+	{ 3, 125000 },
+	{ 6, 250000 },
+	{ 12, 500000 },
+	{ 25, 0 },
+	{ 50, 0 },
+	{ 100, 0 },
+	{ 200, 0 },
+	{ 400, 0 },
+	{ 800, 0 },
+	{ 1600, 0 },
+	{ 3200, 0 },
+};
+
 static int adxl345_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
@@ -108,6 +135,15 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 		 */
 		*val = sign_extend32(regval, 7) * 4;
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		ret = regmap_read(data->regmap, ADXL345_REG_BW_RATE, &regval);
+		if (ret < 0)
+			return ret;
+		regval &= ADXL345_BW_RATE;
+		*val = adxl345_samp_freq_table[regval].val;
+		*val2 = adxl345_samp_freq_table[regval].val2;
+
+		return IIO_VAL_INT_PLUS_MICRO;
 	}
 
 	return -EINVAL;
@@ -118,6 +154,7 @@ static int adxl345_write_raw(struct iio_dev *indio_dev,
 			    int val, int val2, long mask)
 {
 	struct adxl345_data *data = iio_priv(indio_dev);
+	int i;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_CALIBBIAS:
@@ -128,12 +165,36 @@ static int adxl345_write_raw(struct iio_dev *indio_dev,
 		return regmap_write(data->regmap,
 				    ADXL345_REG_OFSX + chan->scan_index,
 				    val / 4);
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		for (i = 0; i < ARRAY_SIZE(adxl345_samp_freq_table); i++) {
+			if (adxl345_samp_freq_table[i].val == val &&
+			    adxl345_samp_freq_table[i].val2 == val2) {
+				return regmap_update_bits(data->regmap,
+							ADXL345_REG_BW_RATE,
+							ADXL345_BW_RATE, i);
+			}
+		}
+		return -EINVAL;
 	}
 
 	return -EINVAL;
 }
 
+static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
+"0.097656 0.195313 0.390625 0.78125 1.5625 3.125 6.25 12.5 25 50 100 200 400 800 1600 3200"
+);
+
+static struct attribute *adxl345_attrs[] = {
+	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group adxl345_attrs_group = {
+	.attrs = adxl345_attrs,
+};
+
 static const struct iio_info adxl345_info = {
+	.attrs		= &adxl345_attrs_group,
 	.read_raw	= adxl345_read_raw,
 	.write_raw	= adxl345_write_raw,
 };
-- 
2.7.4

Re: [PATCH v2 4/4] iio: accel: adxl345: add sampling frequency support

[Andy Shevchenko]

On Mon, Jun 18, 2018 at 6:59 PM, Akinobu Mita <akinobu.mita@gmail.com> wrote:
> The ADXL345 provides selectable output data rate.  This adds the iio
> channel information for the sampling frequency with that feature.

> +static const struct {
> +       int val;
> +       int val2;
> +} adxl345_samp_freq_table[] = {
> +       { 0, 97656 },
> +       { 0, 195313 },
> +       { 0, 390625 },
> +       { 0, 781250 },
> +       { 1, 562500 },
> +       { 3, 125000 },
> +       { 6, 250000 },
> +       { 12, 500000 },
> +       { 25, 0 },
> +       { 50, 0 },
> +       { 100, 0 },
> +       { 200, 0 },
> +       { 400, 0 },
> +       { 800, 0 },
> +       { 1600, 0 },
> +       { 3200, 0 },
> +};

So, this is effectively a just formula with a bit shifts (index is an
exponent) and point of origin.
Why to keep ugly table?

-- 
With Best Regards,
Andy Shevchenko