staging: iio: adt7316: dac fixes

The value of dac_bits is used in adt7316_show_DAC() and adt7316_store_DAC(), and it should be either 8, 10, or 12 bits depending on the device in use. The driver currently only assigns a value to dac_bits in adt7316_store_da_high_resolution(). The purpose of the dac high resolution option is not to change dac resolution for normal operation. Instead, it is specific to an optional feature where one or two of the four dacs can be set to output voltage proportional to temperature. If the user chooses to set dac a and/or dac b to output voltage proportional to temperature, the da_high_resolution attribute can optionally be enabled to use 10 bit resolution rather than the default 8 bits. This is only available on the 10 and 12 bit dac devices. If the user attempts to read or write dacs a or b under these settings, the driver's current behaviour is to return an error. Dacs c and d continue to operate normally under these conditions. With the above in mind, remove the dac_bits assignments from this function since the value of dac_bits as used in the driver is not dependent on this dac high resolution option.

Since the dac_bits assignments discussed above are currently the only ones in this driver, the default value of dac_bits is 0. This results in incorrect calculations when the dacs are read or written in adt7316_show_DAC() and adt7316_store_DAC(). To correct this, assign a value to dac_bits in adt7316_probe() to ensure correct operation as soon as the device is registered and available to userspace.

Fixes 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")

Signed-off-by Jeremy Fertic <[email protected]>

---
 drivers/staging/iio/addac/adt7316.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

drivers/staging/iio/addac/adt7316.c +9 -9

index 9db49aa186bb..e17c1cb12c94 100644
@@ -652,17 +652,10 @@ static ssize_t adt7316_store_da_high_resolution(struct device *dev,
 	u8 config3;
 	int ret;
 
-	chip->dac_bits = 8;
-
-	if (buf[0] == '1') {
+	if (buf[0] == '1')
 		config3 = chip->config3 | ADT7316_DA_HIGH_RESOLUTION;
-		if (chip->id == ID_ADT7316 || chip->id == ID_ADT7516)
-			chip->dac_bits = 12;
-		else if (chip->id == ID_ADT7317 || chip->id == ID_ADT7517)
-			chip->dac_bits = 10;
-	} else {
+	else
 		config3 = chip->config3 & (~ADT7316_DA_HIGH_RESOLUTION);
-	}
 
 	ret = chip->bus.write(chip->bus.client, ADT7316_CONFIG3, config3);
 	if (ret)

@@ -2145,6 +2138,13 @@ int adt7316_probe(struct device *dev, struct adt7316_bus *bus,
 	else
 		return -ENODEV;
 
+	if (chip->id == ID_ADT7316 || chip->id == ID_ADT7516)
+		chip->dac_bits = 12;
+	else if (chip->id == ID_ADT7317 || chip->id == ID_ADT7517)
+		chip->dac_bits = 10;
+	else
+		chip->dac_bits = 8;
+
 	chip->ldac_pin = devm_gpiod_get_optional(dev, "adi,ldac", GPIOD_OUT_LOW);
 	if (IS_ERR(chip->ldac_pin)) {
 		ret = PTR_ERR(chip->ldac_pin);

The adt7316/7 and adt7516/7 have the option to output voltage proportional to temperature on dac a and/or dac b. The default dac resolution in this mode is 8 bits with the dac high resolution option enabling 10 bits. None of these settings affect dacs c and d. Remove the "1 (12 bits)" output from the show function since that is not an option for this mode. Return "1 (10 bits)" if the device is one of the above mentioned chips and the dac high resolution mode is enabled.

In the store function, the driver currently allows the user to write to the ADT7316_DA_HIGH_RESOLUTION bit regardless of the device in use. Add a check to return an error in the case of an adt7318 or adt7519. Remove the else statement that clears the ADT7316_DA_HIGH_RESOLUTION bit. Instead, clear it before conditionally enabling it, depending on user input. This matches the typical pattern in the driver when an attribute is a boolean.

Fixes 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")

Signed-off-by Jeremy Fertic <[email protected]>

---
 drivers/staging/iio/addac/adt7316.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

drivers/staging/iio/addac/adt7316.c +6 -6

index e17c1cb12c94..80cc3420036b 100644
@@ -633,9 +633,7 @@ static ssize_t adt7316_show_da_high_resolution(struct device *dev,
 	struct adt7316_chip_info *chip = iio_priv(dev_info);
 
 	if (chip->config3 & ADT7316_DA_HIGH_RESOLUTION) {
-		if (chip->id == ID_ADT7316 || chip->id == ID_ADT7516)
-			return sprintf(buf, "1 (12 bits)\n");
-		if (chip->id == ID_ADT7317 || chip->id == ID_ADT7517)
+		if (chip->id != ID_ADT7318 && chip->id != ID_ADT7519)
 			return sprintf(buf, "1 (10 bits)\n");
 	}
 

@@ -652,10 +650,12 @@ static ssize_t adt7316_store_da_high_resolution(struct device *dev,
 	u8 config3;
 	int ret;
 
+	if (chip->id == ID_ADT7318 || chip->id == ID_ADT7519)
+		return -EPERM;
+
+	config3 = chip->config3 & (~ADT7316_DA_HIGH_RESOLUTION);
 	if (buf[0] == '1')
-		config3 = chip->config3 | ADT7316_DA_HIGH_RESOLUTION;
-	else
-		config3 = chip->config3 & (~ADT7316_DA_HIGH_RESOLUTION);
+		config3 |= ADT7316_DA_HIGH_RESOLUTION;
 
 	ret = chip->bus.write(chip->bus.client, ADT7316_CONFIG3, config3);
 	if (ret)

The calculation of the current dac value is using the wrong bits of the dac lsb register. Create two macros to shift the lsb register value into lsb position, depending on whether the dac is 10 or 12 bit. Initialize data to 0 so, with an 8 bit dac, the msb register value can be bitwise ORed with data.

Fixes 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")

Signed-off-by Jeremy Fertic <[email protected]>

---
 drivers/staging/iio/addac/adt7316.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

drivers/staging/iio/addac/adt7316.c +8 -2

index 80cc3420036b..d7f3d68e525b 100644
@@ -47,6 +47,8 @@
 #define ADT7516_MSB_AIN3		0xA
 #define ADT7516_MSB_AIN4		0xB
 #define ADT7316_DA_DATA_BASE		0x10
+#define ADT7316_DA_10_BIT_LSB_SHIFT	6
+#define ADT7316_DA_12_BIT_LSB_SHIFT	4
 #define ADT7316_DA_MSB_DATA_REGS	4
 #define ADT7316_LSB_DAC_A		0x10
 #define ADT7316_MSB_DAC_A		0x11

@@ -1392,7 +1394,7 @@ static IIO_DEVICE_ATTR(ex_analog_temp_offset, 0644,
 static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
 				int channel, char *buf)
 {
-	u16 data;
+	u16 data = 0;
 	u8 msb, lsb, offset;
 	int ret;
 

@@ -1417,7 +1419,11 @@ static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
 	if (ret)
 		return -EIO;
 
-	data = (msb << offset) + (lsb & ((1 << offset) - 1));
+	if (chip->dac_bits == 12)
+		data = lsb >> ADT7316_DA_12_BIT_LSB_SHIFT;
+	else if (chip->dac_bits == 10)
+		data = lsb >> ADT7316_DA_10_BIT_LSB_SHIFT;
+	data |= msb << offset;
 
 	return sprintf(buf, "%d\n", data);
 }

The lsb calculation is not masking the correct bits from the user input. Subtract 1 from (1 << offset) to correctly set up the mask to be applied to user input.

The lsb register stores its value starting at the bit 7 position. adt7316_store_DAC() currently assumes the value is at the other end of the register. Shift the lsb value before storing it in a new variable lsb_reg, and write this variable to the lsb register.

Fixes 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")

Signed-off-by Jeremy Fertic <[email protected]>

---
 drivers/staging/iio/addac/adt7316.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

drivers/staging/iio/addac/adt7316.c +7 -3

index d7f3d68e525b..6f7891b567b9 100644
@@ -1431,7 +1431,7 @@ static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
 static ssize_t adt7316_store_DAC(struct adt7316_chip_info *chip,
 				 int channel, const char *buf, size_t len)
 {
-	u8 msb, lsb, offset;
+	u8 msb, lsb, lsb_reg, offset;
 	u16 data;
 	int ret;
 

@@ -1449,9 +1449,13 @@ static ssize_t adt7316_store_DAC(struct adt7316_chip_info *chip,
 		return -EINVAL;
 
 	if (chip->dac_bits > 8) {
-		lsb = data & (1 << offset);
+		lsb = data & ((1 << offset) - 1);
+		if (chip->dac_bits == 12)
+			lsb_reg = lsb << ADT7316_DA_12_BIT_LSB_SHIFT;
+		else
+			lsb_reg = lsb << ADT7316_DA_10_BIT_LSB_SHIFT;
 		ret = chip->bus.write(chip->bus.client,
-			ADT7316_DA_DATA_BASE + channel * 2, lsb);
+			ADT7316_DA_DATA_BASE + channel * 2, lsb_reg);
 		if (ret)
 			return -EIO;
 	}