Subject: [PATCH v2 2/9] thermal: qcom: tsens-8916: Add support for 8916 family of SoCs

From: [email-masked] (Rajendra Nayak)
Date: Mon, 21 Sep 2015 09:58:17 +0530

[]..

>> +static inline int code_to_degc(u32 adc_code, const struct tsens_sensor *s)
>> +{
>> +	int degc, num, den;
>> +
>> +	num = (adc_code * SLOPE_FACTOR) - s->offset;
>> +	den = s->slope;
>> +
>> +	if (num > 0)
>> +		degc = num + (den / 2);
>> +	else if (num < 0)
>> +		degc = num - (den / 2);
>> +	else
>> +		degc = num;
>> +
>> +	degc /= den;
>> +
>> +	return degc;
>> +}
>> +
>> +int get_temp_common(struct tsens_device *tmdev, int id, int *temp)
>> +{
>> +	struct tsens_sensor *s = &tmdev->sensor[id];
>> +	u32 code;
>> +	unsigned int sensor_addr;
>> +	int last_temp = 0, ret;
>> +
>> +	sensor_addr = S0_ST_ADDR + s->hw_id * SN_ADDR_OFFSET;
>> +	ret = regmap_read(tmdev->map, sensor_addr, &code);
>> +	if (ret)
>> +		return ret;
>> +	last_temp = code & SN_ST_TEMP_MASK;
>> +
>> +	*temp = code_to_degc(last_temp, s) * 1000;
>> +
>> +	return 0;
>> +}
>
> The way this function is coded the temperature will only ever change by
> 1C (i.e., 1000mC). Is there a chance that you're losing precision in the
> code_to_degc conversion that could be preserved perhaps?
>
> This is useful in scenarios where you use the power allocator governor
> and the greater precision allows better power budget estimation.

I'll take a look to see if we can get better precision. Thanks.

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