[PATCH v3 0/2] iio: temperature: mlx90632: Add extended calibration calculations

[PATCH v3 0/2] iio: temperature: mlx90632: Add extended calibration calculations

[Crt Mori]

Since the second patch is dependent on the first and was still not
merged, I have decided to send them together. First patch just makes
second one more readable as it splits out the repeated calculation and
that enables the second patch to tweak the variable to the new
condition.

Crt Mori (2):
  iio:temperature:mlx90632: Reduce number of equal calulcations
  iio:temperature:mlx90632: Adding extended calibration option

 drivers/iio/temperature/mlx90632.c | 233 +++++++++++++++++++++++++++--
 1 file changed, 223 insertions(+), 10 deletions(-)

-- 
2.25.1

[PATCH v3 1/2] iio:temperature:mlx90632: Reduce number of equal calulcations

[Crt Mori]

TAdut4 was calculated each iteration although it did not change. In light
of near future additions of the Extended range DSP calculations, this
function refactoring will help reduce unrelated changes in that series as
well as reduce the number of new functions needed.

Signed-off-by: Crt Mori <cmo@melexis.com>
---
 drivers/iio/temperature/mlx90632.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/temperature/mlx90632.c b/drivers/iio/temperature/mlx90632.c
index 51b812bcff2e..763a148a0095 100644
--- a/drivers/iio/temperature/mlx90632.c
+++ b/drivers/iio/temperature/mlx90632.c
@@ -374,11 +374,11 @@ static s32 mlx90632_calc_temp_ambient(s16 ambient_new_raw, s16 ambient_old_raw,
 }
 
 static s32 mlx90632_calc_temp_object_iteration(s32 prev_object_temp, s64 object,
-					       s64 TAdut, s32 Fa, s32 Fb,
+					       s64 TAdut, s64 TAdut4, s32 Fa, s32 Fb,
 					       s32 Ga, s16 Ha, s16 Hb,
 					       u16 emissivity)
 {
-	s64 calcedKsTO, calcedKsTA, ir_Alpha, TAdut4, Alpha_corr;
+	s64 calcedKsTO, calcedKsTA, ir_Alpha, Alpha_corr;
 	s64 Ha_customer, Hb_customer;
 
 	Ha_customer = ((s64)Ha * 1000000LL) >> 14ULL;
@@ -393,10 +393,6 @@ static s32 mlx90632_calc_temp_object_iteration(s32 prev_object_temp, s64 object,
 	Alpha_corr = emissivity * div64_s64(Alpha_corr, 100000LL);
 	Alpha_corr = div64_s64(Alpha_corr, 1000LL);
 	ir_Alpha = div64_s64((s64)object * 10000000LL, Alpha_corr);
-	TAdut4 = (div64_s64(TAdut, 10000LL) + 27315) *
-		(div64_s64(TAdut, 10000LL) + 27315) *
-		(div64_s64(TAdut, 10000LL)  + 27315) *
-		(div64_s64(TAdut, 10000LL) + 27315);
 
 	return (int_sqrt64(int_sqrt64(ir_Alpha * 1000000000000LL + TAdut4))
 		- 27315 - Hb_customer) * 10;
@@ -406,17 +402,21 @@ static s32 mlx90632_calc_temp_object(s64 object, s64 ambient, s32 Ea, s32 Eb,
 				     s32 Fa, s32 Fb, s32 Ga, s16 Ha, s16 Hb,
 				     u16 tmp_emi)
 {
-	s64 kTA, kTA0, TAdut;
+	s64 kTA, kTA0, TAdut, TAdut4;
 	s64 temp = 25000;
 	s8 i;
 
 	kTA = (Ea * 1000LL) >> 16LL;
 	kTA0 = (Eb * 1000LL) >> 8LL;
 	TAdut = div64_s64(((ambient - kTA0) * 1000000LL), kTA) + 25 * 1000000LL;
+	TAdut4 = (div64_s64(TAdut, 10000LL) + 27315) *
+		(div64_s64(TAdut, 10000LL) + 27315) *
+		(div64_s64(TAdut, 10000LL)  + 27315) *
+		(div64_s64(TAdut, 10000LL) + 27315);
 
 	/* Iterations of calculation as described in datasheet */
 	for (i = 0; i < 5; ++i) {
-		temp = mlx90632_calc_temp_object_iteration(temp, object, TAdut,
+		temp = mlx90632_calc_temp_object_iteration(temp, object, TAdut, TAdut4,
 							   Fa, Fb, Ga, Ha, Hb,
 							   tmp_emi);
 	}
-- 
2.25.1

[PATCH v3 2/2] iio:temperature:mlx90632: Adding extended calibration option

[Crt Mori]

For some time the market wants medical grade accuracy in medical range,
while still retaining the declared accuracy outside of the medical range
within the same sensor. That is why we created extended calibration
which is automatically switched to when object temperature is too high.

This patch also introduces the object_ambient_temperature variable which
is needed for more accurate calculation of the object infra-red
footprint as sensor's ambient temperature might be totally different
than what the ambient temperature is at object and that is why we can
have some more errors which can be eliminated. Currently this temperature
is fixed at 25, but the interface to adjust it by user (with external
sensor or just IR measurement of the other object which acts as ambient),
will be introduced in another commit.

Signed-off-by: Crt Mori <cmo@melexis.com>
---
 drivers/iio/temperature/mlx90632.c | 225 ++++++++++++++++++++++++++++-
 1 file changed, 219 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/temperature/mlx90632.c b/drivers/iio/temperature/mlx90632.c
index 763a148a0095..049c1217a166 100644
--- a/drivers/iio/temperature/mlx90632.c
+++ b/drivers/iio/temperature/mlx90632.c
@@ -11,6 +11,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/kernel.h>
+#include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/math64.h>
 #include <linux/of.h>
@@ -58,6 +59,8 @@
 /* Control register address - volatile */
 #define MLX90632_REG_CONTROL	0x3001 /* Control Register address */
 #define   MLX90632_CFG_PWR_MASK		GENMASK(2, 1) /* PowerMode Mask */
+#define   MLX90632_CFG_MTYP_MASK		GENMASK(8, 4) /* Meas select Mask */
+
 /* PowerModes statuses */
 #define MLX90632_PWR_STATUS(ctrl_val) (ctrl_val << 1)
 #define MLX90632_PWR_STATUS_HALT MLX90632_PWR_STATUS(0) /* hold */
@@ -65,6 +68,18 @@
 #define MLX90632_PWR_STATUS_STEP MLX90632_PWR_STATUS(2) /* step */
 #define MLX90632_PWR_STATUS_CONTINUOUS MLX90632_PWR_STATUS(3) /* continuous*/
 
+/* Measurement types */
+#define MLX90632_MTYP_MEDICAL 0
+#define MLX90632_MTYP_EXTENDED 17
+
+/* Measurement type select*/
+#define MLX90632_MTYP_STATUS(ctrl_val) (ctrl_val << 4)
+#define MLX90632_MTYP_STATUS_MEDICAL MLX90632_MTYP_STATUS(MLX90632_MTYP_MEDICAL)
+#define MLX90632_MTYP_STATUS_EXTENDED MLX90632_MTYP_STATUS(MLX90632_MTYP_EXTENDED)
+
+/* I2C command register - volatile */
+#define MLX90632_REG_I2C_CMD    0x3005 /* I2C command Register address */
+
 /* Device status register - volatile */
 #define MLX90632_REG_STATUS	0x3fff /* Device status register */
 #define   MLX90632_STAT_BUSY		BIT(10) /* Device busy indicator */
@@ -81,6 +96,8 @@
 /* Magic constants */
 #define MLX90632_ID_MEDICAL	0x0105 /* EEPROM DSPv5 Medical device id */
 #define MLX90632_ID_CONSUMER	0x0205 /* EEPROM DSPv5 Consumer device id */
+#define MLX90632_ID_EXTENDED	0x0505 /* EEPROM DSPv5 Extended range device id */
+#define MLX90632_ID_MASK	GENMASK(14, 0) /* DSP version and device ID in EE_VERSION */
 #define MLX90632_DSP_VERSION	5 /* DSP version */
 #define MLX90632_DSP_MASK	GENMASK(7, 0) /* DSP version in EE_VERSION */
 #define MLX90632_RESET_CMD	0x0006 /* Reset sensor (address or global) */
@@ -88,16 +105,20 @@
 #define MLX90632_REF_3		12LL /**< ResCtrlRef value of Channel 3 */
 #define MLX90632_MAX_MEAS_NUM	31 /**< Maximum measurements in list */
 #define MLX90632_SLEEP_DELAY_MS 3000 /**< Autosleep delay */
+#define MLX90632_EXTENDED_LIMIT 27000 /* Extended mode raw value limit */
 
 struct mlx90632_data {
 	struct i2c_client *client;
 	struct mutex lock; /* Multiple reads for single measurement */
 	struct regmap *regmap;
 	u16 emissivity;
+	u8 mtyp; /* measurement type - to enable extended range calculations */
+	u32 object_ambient_temperature;
 };
 
 static const struct regmap_range mlx90632_volatile_reg_range[] = {
 	regmap_reg_range(MLX90632_REG_I2C_ADDR, MLX90632_REG_CONTROL),
+	regmap_reg_range(MLX90632_REG_I2C_CMD, MLX90632_REG_I2C_CMD),
 	regmap_reg_range(MLX90632_REG_STATUS, MLX90632_REG_STATUS),
 	regmap_reg_range(MLX90632_RAM_1(0),
 			 MLX90632_RAM_3(MLX90632_MAX_MEAS_NUM)),
@@ -113,6 +134,7 @@ static const struct regmap_range mlx90632_read_reg_range[] = {
 	regmap_reg_range(MLX90632_EE_CTRL, MLX90632_EE_I2C_ADDR),
 	regmap_reg_range(MLX90632_EE_Ha, MLX90632_EE_Hb),
 	regmap_reg_range(MLX90632_REG_I2C_ADDR, MLX90632_REG_CONTROL),
+	regmap_reg_range(MLX90632_REG_I2C_CMD, MLX90632_REG_I2C_CMD),
 	regmap_reg_range(MLX90632_REG_STATUS, MLX90632_REG_STATUS),
 	regmap_reg_range(MLX90632_RAM_1(0),
 			 MLX90632_RAM_3(MLX90632_MAX_MEAS_NUM)),
@@ -199,6 +221,26 @@ static int mlx90632_perform_measurement(struct mlx90632_data *data)
 	return (reg_status & MLX90632_STAT_CYCLE_POS) >> 2;
 }
 
+static int mlx90632_set_meas_type(struct regmap *regmap, u8 type)
+{
+	int ret;
+
+	if ((type != MLX90632_MTYP_MEDICAL) && (type != MLX90632_MTYP_EXTENDED))
+		return -EINVAL;
+
+	ret = regmap_write(regmap, MLX90632_REG_I2C_CMD, MLX90632_RESET_CMD);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_write_bits(regmap, MLX90632_REG_CONTROL,
+				 (MLX90632_CFG_MTYP_MASK | MLX90632_CFG_PWR_MASK),
+				 (MLX90632_MTYP_STATUS(type) | MLX90632_PWR_STATUS_HALT));
+	if (ret < 0)
+		return ret;
+
+	return mlx90632_pwr_continuous(regmap);
+}
+
 static int mlx90632_channel_new_select(int perform_ret, uint8_t *channel_new,
 				       uint8_t *channel_old)
 {
@@ -300,6 +342,106 @@ static int mlx90632_read_all_channel(struct mlx90632_data *data,
 	return ret;
 }
 
+static int mlx90632_read_ambient_raw_extended(struct regmap *regmap,
+					      s16 *ambient_new_raw, s16 *ambient_old_raw)
+{
+	unsigned int read_tmp;
+	int ret;
+
+	ret = regmap_read(regmap, MLX90632_RAM_3(17), &read_tmp);
+	if (ret < 0)
+		return ret;
+	*ambient_new_raw = (s16)read_tmp;
+
+	ret = regmap_read(regmap, MLX90632_RAM_3(18), &read_tmp);
+	if (ret < 0)
+		return ret;
+	*ambient_old_raw = (s16)read_tmp;
+
+	return 0;
+}
+
+static int mlx90632_read_object_raw_extended(struct regmap *regmap, s16 *object_new_raw)
+{
+	unsigned int read_tmp;
+	s32 read;
+	int ret;
+
+	ret = regmap_read(regmap, MLX90632_RAM_1(17), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = (s16)read_tmp;
+
+	ret = regmap_read(regmap, MLX90632_RAM_2(17), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = read - (s16)read_tmp;
+
+	ret = regmap_read(regmap, MLX90632_RAM_1(18), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = read - (s16)read_tmp;
+
+	ret = regmap_read(regmap, MLX90632_RAM_2(18), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = (read + (s16)read_tmp) / 2;
+
+	ret = regmap_read(regmap, MLX90632_RAM_1(19), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = read + (s16)read_tmp;
+
+	ret = regmap_read(regmap, MLX90632_RAM_2(19), &read_tmp);
+	if (ret < 0)
+		return ret;
+	read = read + (s16)read_tmp;
+
+	if (read > S16_MAX || read < S16_MIN)
+		return -ERANGE;
+
+	*object_new_raw = read;
+
+	return 0;
+}
+
+static int mlx90632_read_all_channel_extended(struct mlx90632_data *data, s16 *object_new_raw,
+					      s16 *ambient_new_raw, s16 *ambient_old_raw)
+{
+	int tries = 4;
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = mlx90632_set_meas_type(data->regmap, MLX90632_MTYP_EXTENDED);
+	if (ret < 0)
+		goto read_unlock;
+
+	while (tries-- > 0) {
+		ret = mlx90632_perform_measurement(data);
+		if (ret < 0)
+			goto read_unlock;
+
+		if (ret == 19)
+			break;
+	}
+	if (tries < 0) {
+		ret = -ETIMEDOUT;
+		goto read_unlock;
+	}
+
+	ret = mlx90632_read_object_raw_extended(data->regmap, object_new_raw);
+	if (ret < 0)
+		goto read_unlock;
+
+	ret = mlx90632_read_ambient_raw_extended(data->regmap, ambient_new_raw, ambient_old_raw);
+
+read_unlock:
+	(void) mlx90632_set_meas_type(data->regmap, MLX90632_MTYP_MEDICAL);
+
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
 static int mlx90632_read_ee_register(struct regmap *regmap, u16 reg_lsb,
 				     s32 *reg_value)
 {
@@ -354,9 +496,23 @@ static s64 mlx90632_preprocess_temp_obj(s16 object_new_raw, s16 object_old_raw,
 	return div64_s64((tmp << 19ULL), 1000LL);
 }
 
+static s64 mlx90632_preprocess_temp_obj_extended(s16 object_new_raw, s16 ambient_new_raw,
+						 s16 ambient_old_raw, s16 Ka)
+{
+	s64 VR_IR, kKa, tmp;
+
+	kKa = ((s64)Ka * 1000LL) >> 10ULL;
+	VR_IR = (s64)ambient_old_raw * 1000000LL +
+		kKa * div64_s64((s64)ambient_new_raw * 1000LL,
+				MLX90632_REF_3);
+	tmp = div64_s64(
+			div64_s64((s64) object_new_raw * 1000000000000LL, MLX90632_REF_12),
+			VR_IR);
+	return div64_s64(tmp << 19ULL, 1000LL);
+}
+
 static s32 mlx90632_calc_temp_ambient(s16 ambient_new_raw, s16 ambient_old_raw,
-				      s32 P_T, s32 P_R, s32 P_G, s32 P_O,
-				      s16 Gb)
+				      s32 P_T, s32 P_R, s32 P_G, s32 P_O, s16 Gb)
 {
 	s64 Asub, Bsub, Ablock, Bblock, Cblock, AMB, sum;
 
@@ -398,6 +554,14 @@ static s32 mlx90632_calc_temp_object_iteration(s32 prev_object_temp, s64 object,
 		- 27315 - Hb_customer) * 10;
 }
 
+static s64 mlx90632_calc_ta4(s64 TAdut, s64 scale)
+{
+	return (div64_s64(TAdut, scale) + 27315) *
+		(div64_s64(TAdut, scale) + 27315) *
+		(div64_s64(TAdut, scale) + 27315) *
+		(div64_s64(TAdut, scale) + 27315);
+}
+
 static s32 mlx90632_calc_temp_object(s64 object, s64 ambient, s32 Ea, s32 Eb,
 				     s32 Fa, s32 Fb, s32 Ga, s16 Ha, s16 Hb,
 				     u16 tmp_emi)
@@ -409,10 +573,7 @@ static s32 mlx90632_calc_temp_object(s64 object, s64 ambient, s32 Ea, s32 Eb,
 	kTA = (Ea * 1000LL) >> 16LL;
 	kTA0 = (Eb * 1000LL) >> 8LL;
 	TAdut = div64_s64(((ambient - kTA0) * 1000000LL), kTA) + 25 * 1000000LL;
-	TAdut4 = (div64_s64(TAdut, 10000LL) + 27315) *
-		(div64_s64(TAdut, 10000LL) + 27315) *
-		(div64_s64(TAdut, 10000LL)  + 27315) *
-		(div64_s64(TAdut, 10000LL) + 27315);
+	TAdut4 = mlx90632_calc_ta4(TAdut, 10000LL);
 
 	/* Iterations of calculation as described in datasheet */
 	for (i = 0; i < 5; ++i) {
@@ -423,6 +584,31 @@ static s32 mlx90632_calc_temp_object(s64 object, s64 ambient, s32 Ea, s32 Eb,
 	return temp;
 }
 
+static s32 mlx90632_calc_temp_object_extended(s64 object, s64 ambient, s64 reflected,
+					      s32 Ea, s32 Eb, s32 Fa, s32 Fb, s32 Ga,
+					      s16 Ha, s16 Hb, u16 tmp_emi)
+{
+	s64 kTA, kTA0, TAdut, TAdut4, Tr4, TaTr4;
+	s64 temp = 25000;
+	s8 i;
+
+	kTA = (Ea * 1000LL) >> 16LL;
+	kTA0 = (Eb * 1000LL) >> 8LL;
+	TAdut = div64_s64(((ambient - kTA0) * 1000000LL), kTA) + 25 * 1000000LL;
+	Tr4 = mlx90632_calc_ta4(reflected, 10);
+	TAdut4 = mlx90632_calc_ta4(TAdut, 10000LL);
+	TaTr4 = Tr4 - div64_s64(Tr4 - TAdut4, tmp_emi) * 1000;
+
+	/* Iterations of calculation as described in datasheet */
+	for (i = 0; i < 5; ++i) {
+		temp = mlx90632_calc_temp_object_iteration(temp, object, TAdut, TaTr4,
+							   Fa / 2, Fb, Ga, Ha, Hb,
+							   tmp_emi);
+	}
+
+	return temp;
+}
+
 static int mlx90632_calc_object_dsp105(struct mlx90632_data *data, int *val)
 {
 	s32 ret;
@@ -470,6 +656,26 @@ static int mlx90632_calc_object_dsp105(struct mlx90632_data *data, int *val)
 	if (ret < 0)
 		return ret;
 
+	if (object_new_raw > MLX90632_EXTENDED_LIMIT &&
+	    data->mtyp == MLX90632_MTYP_EXTENDED) {
+		ret = mlx90632_read_all_channel_extended(data, &object_new_raw,
+							 &ambient_new_raw, &ambient_old_raw);
+		if (ret < 0)
+			return ret;
+
+		/* Use extended mode calculations */
+		ambient = mlx90632_preprocess_temp_amb(ambient_new_raw,
+						       ambient_old_raw, Gb);
+		object = mlx90632_preprocess_temp_obj_extended(object_new_raw,
+							       ambient_new_raw,
+							       ambient_old_raw, Ka);
+		*val = mlx90632_calc_temp_object_extended(object, ambient,
+							  data->object_ambient_temperature,
+							  Ea, Eb, Fa, Fb, Ga,
+							  Ha, Hb, data->emissivity);
+		return 0;
+	}
+
 	ambient = mlx90632_preprocess_temp_amb(ambient_new_raw,
 					       ambient_old_raw, Gb);
 	object = mlx90632_preprocess_temp_obj(object_new_raw,
@@ -643,6 +849,7 @@ static int mlx90632_probe(struct i2c_client *client,
 	i2c_set_clientdata(client, indio_dev);
 	mlx90632->client = client;
 	mlx90632->regmap = regmap;
+	mlx90632->mtyp = MLX90632_MTYP_MEDICAL;
 
 	mutex_init(&mlx90632->lock);
 	indio_dev->name = id->name;
@@ -662,12 +869,17 @@ static int mlx90632_probe(struct i2c_client *client,
 		dev_err(&client->dev, "read of version failed: %d\n", ret);
 		return ret;
 	}
+	read = read & MLX90632_ID_MASK;
 	if (read == MLX90632_ID_MEDICAL) {
 		dev_dbg(&client->dev,
 			"Detected Medical EEPROM calibration %x\n", read);
 	} else if (read == MLX90632_ID_CONSUMER) {
 		dev_dbg(&client->dev,
 			"Detected Consumer EEPROM calibration %x\n", read);
+	} else if (read == MLX90632_ID_EXTENDED) {
+		dev_dbg(&client->dev,
+			"Detected Extended range EEPROM calibration %x\n", read);
+		mlx90632->mtyp = MLX90632_MTYP_EXTENDED;
 	} else if ((read & MLX90632_DSP_MASK) == MLX90632_DSP_VERSION) {
 		dev_dbg(&client->dev,
 			"Detected Unknown EEPROM calibration %x\n", read);	
@@ -679,6 +891,7 @@ static int mlx90632_probe(struct i2c_client *client,
 	}
 
 	mlx90632->emissivity = 1000;
+	mlx90632->object_ambient_temperature = 25000; /* 25 degrees milliCelsius */
 
 	pm_runtime_disable(&client->dev);
 	ret = pm_runtime_set_active(&client->dev);
-- 
2.25.1

Re: [PATCH v3 0/2] iio: temperature: mlx90632: Add extended calibration calculations

[Andy Shevchenko]

On Sat, Aug 8, 2020 at 2:22 AM Crt Mori <cmo@melexis.com> wrote:
>
> Since the second patch is dependent on the first and was still not
> merged, I have decided to send them together. First patch just makes
> second one more readable as it splits out the repeated calculation and
> that enables the second patch to tweak the variable to the new
> condition.

Neither here nor in the individual patches I haven't found a changelog.

> Crt Mori (2):
>   iio:temperature:mlx90632: Reduce number of equal calulcations
>   iio:temperature:mlx90632: Adding extended calibration option
>
>  drivers/iio/temperature/mlx90632.c | 233 +++++++++++++++++++++++++++--
>  1 file changed, 223 insertions(+), 10 deletions(-)
>
> --
> 2.25.1
>


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 1/2] iio:temperature:mlx90632: Reduce number of equal calulcations

[Andy Shevchenko]

On Sat, Aug 8, 2020 at 2:22 AM Crt Mori <cmo@melexis.com> wrote:
>
> TAdut4 was calculated each iteration although it did not change. In light
> of near future additions of the Extended range DSP calculations, this
> function refactoring will help reduce unrelated changes in that series as
> well as reduce the number of new functions needed.

I see you provided a helper for this calculus, but I think we may
reduce a lot of churn if you do the following:
- introduce helper and convert one/current user (no functional change!)
- do what you did in this patch, but it will move less LOCs
- do what you have done in the next one using the helper

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 2/2] iio:temperature:mlx90632: Adding extended calibration option

[Andy Shevchenko]

On Sat, Aug 8, 2020 at 2:24 AM Crt Mori <cmo@melexis.com> wrote:
>
> For some time the market wants medical grade accuracy in medical range,
> while still retaining the declared accuracy outside of the medical range
> within the same sensor. That is why we created extended calibration
> which is automatically switched to when object temperature is too high.
>
> This patch also introduces the object_ambient_temperature variable which
> is needed for more accurate calculation of the object infra-red
> footprint as sensor's ambient temperature might be totally different
> than what the ambient temperature is at object and that is why we can
> have some more errors which can be eliminated. Currently this temperature
> is fixed at 25, but the interface to adjust it by user (with external
> sensor or just IR measurement of the other object which acts as ambient),
> will be introduced in another commit.

Thank you for an update!
My comments below.

...

>  struct mlx90632_data {
>         struct i2c_client *client;
>         struct mutex lock; /* Multiple reads for single measurement */
>         struct regmap *regmap;
>         u16 emissivity;
> +       u8 mtyp; /* measurement type - to enable extended range calculations */
> +       u32 object_ambient_temperature;
>  };

As a separate patch to have a kernel doc for this, there are plenty of
examples in the kernel, but I will show below an example

/**
 * struct foo - private data for the MLX90632 device
 * @client: I2C client of the device
 * @bar: ...
 ...
 */
struct foo {
  struct i2c_client *client;
  ... bar;
  ...
};

...

> +       if ((type != MLX90632_MTYP_MEDICAL) && (type != MLX90632_MTYP_EXTENDED))
> +               return -EINVAL;

So, just to point out what the difference between & and &&  (even for
boolean): the former one forces both sides of operand to be executed,
while && checks for only first in case of false.

...

> +static int mlx90632_read_ambient_raw_extended(struct regmap *regmap,
> +                                             s16 *ambient_new_raw, s16 *ambient_old_raw)
> +{
> +       unsigned int read_tmp;
> +       int ret;
> +
> +       ret = regmap_read(regmap, MLX90632_RAM_3(17), &read_tmp);
> +       if (ret < 0)
> +               return ret;
> +       *ambient_new_raw = (s16)read_tmp;

Again the same question, do you need all these castings?

> +       ret = regmap_read(regmap, MLX90632_RAM_3(18), &read_tmp);

These 17, 18 and 19 should be defined with descriptive names.

> +       if (ret < 0)
> +               return ret;
> +       *ambient_old_raw = (s16)read_tmp;
> +
> +       return 0;
> +}

...

> +       int tries = 4;

> +       while (tries-- > 0) {
> +               ret = mlx90632_perform_measurement(data);
> +               if (ret < 0)
> +                       goto read_unlock;
> +
> +               if (ret == 19)
> +                       break;
> +       }
> +       if (tries < 0) {
> +               ret = -ETIMEDOUT;
> +               goto read_unlock;
> +       }

Again, please use

unsigned int tries = 4; // or should be 5?

do {
  ...
} while (ret != ..._ LAST_CHANNEL && --tries);
if (!tries)
  ...

It will really make the code easier to read.

...

> +static s64 mlx90632_preprocess_temp_obj_extended(s16 object_new_raw, s16 ambient_new_raw,
> +                                                s16 ambient_old_raw, s16 Ka)
> +{
> +       s64 VR_IR, kKa, tmp;
> +
> +       kKa = ((s64)Ka * 1000LL) >> 10ULL;
> +       VR_IR = (s64)ambient_old_raw * 1000000LL +
> +               kKa * div64_s64((s64)ambient_new_raw * 1000LL,
> +                               MLX90632_REF_3);
> +       tmp = div64_s64(
> +                       div64_s64((s64) object_new_raw * 1000000000000LL, MLX90632_REF_12),
> +                       VR_IR);
> +       return div64_s64(tmp << 19ULL, 1000LL);
> +}

It would be nice to have a comment on this voodoo arithmetics.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 2/2] iio:temperature:mlx90632: Adding extended calibration option

[Crt Mori]

On Sat, 8 Aug 2020 at 12:44, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
>
> On Sat, Aug 8, 2020 at 2:24 AM Crt Mori <cmo@melexis.com> wrote:
> >
> > For some time the market wants medical grade accuracy in medical range,
> > while still retaining the declared accuracy outside of the medical range
> > within the same sensor. That is why we created extended calibration
> > which is automatically switched to when object temperature is too high.
> >
> > This patch also introduces the object_ambient_temperature variable which
> > is needed for more accurate calculation of the object infra-red
> > footprint as sensor's ambient temperature might be totally different
> > than what the ambient temperature is at object and that is why we can
> > have some more errors which can be eliminated. Currently this temperature
> > is fixed at 25, but the interface to adjust it by user (with external
> > sensor or just IR measurement of the other object which acts as ambient),
> > will be introduced in another commit.
>
> Thank you for an update!
> My comments below.
>

Will provide next version with changelog as well.

> ...
>
> >  struct mlx90632_data {
> >         struct i2c_client *client;
> >         struct mutex lock; /* Multiple reads for single measurement */
> >         struct regmap *regmap;
> >         u16 emissivity;
> > +       u8 mtyp; /* measurement type - to enable extended range calculations */
> > +       u32 object_ambient_temperature;
> >  };
>
> As a separate patch to have a kernel doc for this, there are plenty of
> examples in the kernel, but I will show below an example
>
> /**
>  * struct foo - private data for the MLX90632 device
>  * @client: I2C client of the device
>  * @bar: ...
>  ...
>  */
> struct foo {
>   struct i2c_client *client;
>   ... bar;
>   ...
> };
>
> ...
>
> > +       if ((type != MLX90632_MTYP_MEDICAL) && (type != MLX90632_MTYP_EXTENDED))
> > +               return -EINVAL;
>
> So, just to point out what the difference between & and &&  (even for
> boolean): the former one forces both sides of operand to be executed,
> while && checks for only first in case of false.
>

OK, I am OK with evaluating first only. I mostly thought it is boolean
vs bitwise, but I keep on learning.

> ...
>
> > +static int mlx90632_read_ambient_raw_extended(struct regmap *regmap,
> > +                                             s16 *ambient_new_raw, s16 *ambient_old_raw)
> > +{
> > +       unsigned int read_tmp;
> > +       int ret;
> > +
> > +       ret = regmap_read(regmap, MLX90632_RAM_3(17), &read_tmp);
> > +       if (ret < 0)
> > +               return ret;
> > +       *ambient_new_raw = (s16)read_tmp;
>
> Again the same question, do you need all these castings?
>

These castings are in fact needed. You read unsigned integer, but the
return value is signed integer. Without the cast it did not extend the
signed bit, but just wrote the value to signed. Also I find it more
obvious with casts, that I did not "accidentally" convert to signed.

> > +       ret = regmap_read(regmap, MLX90632_RAM_3(18), &read_tmp);
>
> These 17, 18 and 19 should be defined with descriptive names.
>

When we started 0 to 19 were all open for access, from userspace, then
only 1 and 2 were used with calculations, and now we use 17, 18 and
19. Matter of fact is, I can't provide a descriptive name as it
depends on DSP version and as you can see now within the same DSP
version, also on the ID part. While RAM3 vs RAM1 and RAM2 could be
named RAM_OBJECT1, RAM_OBJECT2, RAM_AMBIENT, knowing our development
that might not be true in the next configuration, so I rather keep the
naming as in the datasheet.

> > +       if (ret < 0)
> > +               return ret;
> > +       *ambient_old_raw = (s16)read_tmp;
> > +
> > +       return 0;
> > +}
>
> ...
>
> > +       int tries = 4;
>
> > +       while (tries-- > 0) {
> > +               ret = mlx90632_perform_measurement(data);
> > +               if (ret < 0)
> > +                       goto read_unlock;
> > +
> > +               if (ret == 19)
> > +                       break;
> > +       }
> > +       if (tries < 0) {
> > +               ret = -ETIMEDOUT;
> > +               goto read_unlock;
> > +       }
>
> Again, please use
>
> unsigned int tries = 4; // or should be 5?
>
> do {
>   ...
> } while (ret != ..._ LAST_CHANNEL && --tries);
> if (!tries)
>   ...
>
> It will really make the code easier to read.
>

I thought of keeping it consistent with the existing implementation in
the perform_measurement function. If you still insist in the loop
change, then I think it is better if I provide a followup patch that
changes both these loops.

> ...
>
> > +static s64 mlx90632_preprocess_temp_obj_extended(s16 object_new_raw, s16 ambient_new_raw,
> > +                                                s16 ambient_old_raw, s16 Ka)
> > +{
> > +       s64 VR_IR, kKa, tmp;
> > +
> > +       kKa = ((s64)Ka * 1000LL) >> 10ULL;
> > +       VR_IR = (s64)ambient_old_raw * 1000000LL +
> > +               kKa * div64_s64((s64)ambient_new_raw * 1000LL,
> > +                               MLX90632_REF_3);
> > +       tmp = div64_s64(
> > +                       div64_s64((s64) object_new_raw * 1000000000000LL, MLX90632_REF_12),
> > +                       VR_IR);
> > +       return div64_s64(tmp << 19ULL, 1000LL);
> > +}
>
> It would be nice to have a comment on this voodoo arithmetics.
>

Honestly, the equation is in the datasheet[1] and this is just making
floating point to fixed point with proper intermediate scaling
(initially I had defines of TENTOX, but that was not desired). There
is no better explanation of this voodoo.

> --
> With Best Regards,
> Andy Shevchenko

[1] https://www.melexis.com/-/media/files/documents/datasheets/mlx90632-datasheet-melexis.pdf