[PATCH V3 2/4] iio: adc: qcom-vadc-common: add reverse scaling for PMIC5 Gen2 ADC_TM

[Jishnu Prakash]

Add reverse scaling function for PMIC5 Gen2 ADC_TM, to convert
temperature to raw ADC code, for setting thresholds for
thermistor channels.

Signed-off-by: Jishnu Prakash <quic_jprakash@xxxxxxxxxxx>
Acked-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
 drivers/iio/adc/qcom-vadc-common.c       | 11 +++++++++++
 include/linux/iio/adc/qcom-vadc-common.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/iio/adc/qcom-vadc-common.c b/drivers/iio/adc/qcom-vadc-common.c
index 1472389..194d7c3 100644
--- a/drivers/iio/adc/qcom-vadc-common.c
+++ b/drivers/iio/adc/qcom-vadc-common.c
@@ -677,6 +677,17 @@ u16 qcom_adc_tm5_temp_volt_scale(unsigned int prescale_ratio,
 }
 EXPORT_SYMBOL(qcom_adc_tm5_temp_volt_scale);
 
+u16 qcom_adc_tm5_gen2_temp_res_scale(int temp)
+{
+	int64_t resistance;
+
+	resistance = qcom_vadc_map_temp_voltage(adcmap7_100k,
+		ARRAY_SIZE(adcmap7_100k), temp);
+
+	return div64_s64(resistance * RATIO_MAX_ADC7, resistance + R_PU_100K);
+}
+EXPORT_SYMBOL(qcom_adc_tm5_gen2_temp_res_scale);
+
 int qcom_adc5_hw_scale(enum vadc_scale_fn_type scaletype,
 		    unsigned int prescale_ratio,
 		    const struct adc5_data *data,
diff --git a/include/linux/iio/adc/qcom-vadc-common.h b/include/linux/iio/adc/qcom-vadc-common.h
index 33f60f4..598a5d2 100644
--- a/include/linux/iio/adc/qcom-vadc-common.h
+++ b/include/linux/iio/adc/qcom-vadc-common.h
@@ -161,6 +161,8 @@ int qcom_adc5_hw_scale(enum vadc_scale_fn_type scaletype,
 u16 qcom_adc_tm5_temp_volt_scale(unsigned int prescale_ratio,
 				 u32 full_scale_code_volt, int temp);
 
+u16 qcom_adc_tm5_gen2_temp_res_scale(int temp);
+
 int qcom_adc5_prescaling_from_dt(u32 num, u32 den);
 
 int qcom_adc5_hw_settle_time_from_dt(u32 value, const unsigned int *hw_settle);
-- 
2.7.4