/**
* adc_to_temp - converts the ADC code to temperature in C
* @direct: true if ths channel is direct index
* @adc_val: the adc_val that needs to be converted
* @tp: temperature return value
*
* Linear approximation is used to covert the skin adc value into temperature.
* This technique is used to avoid very long look-up table to get
* the appropriate temp value from ADC value.
* The adc code vs sensor temp curve is split into five parts
* to achieve very close approximate temp value with less than
* 0.5C error
*/
static int adc_to_temp(int direct, uint16_t adc_val, unsigned long *tp)
{
int temp;
/* Direct conversion for die temperature */
if (direct) {
if (is_valid_adc(adc_val, MSIC_DIE_ADC_MIN, MSIC_DIE_ADC_MAX)) {
*tp = to_msic_die_temp(adc_val) * 1000;
return 0;
}
return -ERANGE;
}
if (!is_valid_adc(adc_val, ADC_MIN, ADC_MAX))
return -ERANGE;
/* Linear approximation for skin temperature */
if (adc_val > ADC_VAL0C)
temp = 177 - (adc_val/5);
else if ((adc_val <= ADC_VAL0C) && (adc_val > ADC_VAL20C))
temp = 111 - (adc_val/8);
else if ((adc_val <= ADC_VAL20C) && (adc_val > ADC_VAL40C))
temp = 92 - (adc_val/10);
else if ((adc_val <= ADC_VAL40C) && (adc_val > ADC_VAL60C))
temp = 91 - (adc_val/10);
else
temp = 112 - (adc_val/6);
/* Convert temperature in celsius to milli degree celsius */
*tp = temp * 1000;
return 0;
}
static int adc_to_temp(int direct, uint16_t adc_val, unsigned long *tp)
{
int temp;
if (direct) {
if (is_valid_adc(adc_val, MSIC_DIE_ADC_MIN, MSIC_DIE_ADC_MAX)) {
*tp = to_msic_die_temp(adc_val) * 1000;
return 0;
}
return -ERANGE;
}
if (!is_valid_adc(adc_val, ADC_MIN, ADC_MAX))
return -ERANGE;
if (adc_val > ADC_VAL0C)
temp = 177 - (adc_val/5);
else if ((adc_val <= ADC_VAL0C) && (adc_val > ADC_VAL20C))
temp = 111 - (adc_val/8);
else if ((adc_val <= ADC_VAL20C) && (adc_val > ADC_VAL40C))
temp = 92 - (adc_val/10);
else if ((adc_val <= ADC_VAL40C) && (adc_val > ADC_VAL60C))
temp = 91 - (adc_val/10);
else
temp = 112 - (adc_val/6);
*tp = temp * 1000;
return 0;
}
