hwmon: qpnp-adc-voltage: Add optional VADC property

Add option to select whether a fresh calibration
needs to be performed when performing the channel measurement.
If the property is not present the default value of
using calibration measurement collected from a timer
will be used. For most cases using a measurement collected
from a timer interval should suffice and the default value
can be used.

Change-Id: I632a9466f04d5d0712de436fc3e1251f7e2e7ad2
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>

Documentation/devicetree/bindings/hwmon/qpnp-adc-voltage.txt

@@ -8,8 +8,8 @@ for the USR peripheral of the VADC.
 VADC node
 
 Required properties:
-- compatible : should be "qcom,qpnp-vadc" for Voltage ADC driver and
-		"qcom,qpnp-vadc-hc" for VADC_HC voltage ADC driver.
+- compatible : should be "qcom,qpnp-vadc" for Voltage ADC device driver and
+		"qcom,qpnp-vadc-hc" for VADC_HC voltage ADC device driver.
 - reg : offset and length of the PMIC Aribter register map.
 - address-cells : Must be one.
 - size-cells : Must be zero.
@@ -40,6 +40,12 @@ Optional properties:
 			   by the thermal framework.
 - hkadc_ldo-supply : Add this property if VADC needs to perform a Software Vote for the HKADC.
 - hkadc_ok-supply : Add this property if the VADC needs to perform a Software vote for the HKADC VREG_OK.
+- qcom,cal-val : Add this property for VADC_HC voltage ADC device to select from the following
+		unsigned int. If the property is not present the default calibration value of
+		using the timer value is chosen.
+		    0 : The calibration values used for measurement are from a timer.
+		    1 : Forces a fresh measurement for calibration values at the same time
+			measurement is taken.
 
 Client required property:
 - qcom,<consumer name>-vadc : The phandle to the corresponding vadc device.
@@ -51,11 +57,15 @@ Required properties:
 - label : Channel name used for sysfs entry.
 - reg : AMUX channel number.
 - qcom,decimation : Sampling rate to use for the individual channel measurement.
-		    Select from following unsigned int.
+		    Select from following unsigned int for Voltage ADC device.
 		    0 : 512
 		    1 : 1K
 		    2 : 2K
 		    3 : 4K
+		    Select from following unsigned int for VADC_HC voltage ADC device.
+		    0 : 256
+		    1 : 512
+		    2 : 1024
 - qcom,pre-div-channel-scaling : Pre-div used for the channel before the signal
 				 is being measured. Some of the AMUX channels
 				 support dividing the signal from a predetermined
@@ -109,7 +119,7 @@ Required properties:
 - qcom,fast-avg-setup : Average number of samples to be used for measurement. Fast averaging
 			provides the option to obtain a single measurement from the ADC that
 			is an average of multiple samples. The value selected is 2^(value)
-			Select from the following unsigned int.
+			Select from the following unsigned int for Voltage ADC device.
 			0 : 1
 			1 : 2
 			2 : 4
@@ -119,6 +129,12 @@ Required properties:
 			6 : 64
 			7 : 128
 			8 : 256
+			Select from the following unsigned int for VADC_HC ADC device.
+			0 : 1
+			1 : 2
+			2 : 4
+			3 : 8
+			4 : 16
 
 Example:
 	/* Main Node */

drivers/hwmon/qpnp-adc-common.c

@@ -1789,7 +1789,7 @@ int32_t qpnp_adc_get_devicetree_data(struct platform_device *pdev,
 	struct qpnp_adc_properties *adc_prop;
 	struct qpnp_adc_amux_properties *amux_prop;
 	int count_adc_channel_list = 0, decimation, rc = 0, i = 0;
-	int decimation_tm_hc = 0, fast_avg_setup_tm_hc = 0;
+	int decimation_tm_hc = 0, fast_avg_setup_tm_hc = 0, cal_val_hc = 0;
 	bool adc_hc;
 
 	if (!node)
@@ -1948,6 +1948,17 @@ int32_t qpnp_adc_get_devicetree_data(struct platform_device *pdev,
 			fast_avg_setup = fast_avg_setup_tm_hc;
 		}
 
+		if (of_device_is_compatible(node, "qcom,qpnp-vadc-hc")) {
+			rc = of_property_read_u32(child, "qcom,cal-val",
+							&cal_val_hc);
+			if (rc) {
+				pr_debug("Use calibration value from timer\n");
+				adc_channel_list[i].cal_val = ADC_TIMER_CAL;
+			} else {
+				adc_channel_list[i].cal_val = cal_val_hc;
+			}
+		}
+
 		/* Individual channel properties */
 		adc_channel_list[i].name = (char *)channel_name;
 		adc_channel_list[i].channel_num = channel_num;