Re: [PATCH] thermal: generic-adc: Fix linear temperature approximation

["Paweł Jarosz" <paweljarosz3691@gmail.com>]

W dniu 20.10.2016 o 14:40, Laxman Dewangan pisze:
>
> On Wednesday 19 October 2016 01:01 AM, Paweł Jarosz wrote:
>> In current version of the driver there is error in temperature
>> calculation.
>>
>> So lets fix it using proper linear function.
>>
>> Signed-off-by: Paweł Jarosz <paweljarosz3691@gmail.com>
>
> Per my calculation, existing and your equation is same as both are 
> doing linear interpolation.
>
> Only think I have seen is that I have used 1000 for two consecutive 
> temp difference and you used (t2 - t1), so your is better in this case 
> but still the equation is same.
>
> The equation from you is
>
>     t1 + (hi -val) * factor.
>
> and existing one is
>      t2 - (val -lo) * factor
>
>
> factor is abs((t2-t1)/(hi-lo))
>
> If my analysis is not correct then can you please provide the example 
> with calculation for better understansing?

Hi

For example if we try to calculate temp for val = 8, i = 1 and table:

<0 9
  2 7>

	adc_hi = gti->lookup_table[2 * i - 1];
	adc_lo = gti->lookup_table[2 * i + 1];
	temp = gti->lookup_table[2 * i];
	temp -= ((val - adc_lo) * 1000) / (adc_hi - adc_lo);

Your method gives temp =  -498

Paweł