On Thu, Dec 22, 2016 at 11:38:19AM +0100, Niklas Söderlund wrote: > Hi all, > > The series adds thermal support to Renesas R-Car Gen3 SoCs. It's tested > on Salvator-X H3 and M3-W SoC. > > Wolfram asked me to have a look at the comments for v4 and to try and > rework the temperature formulas to work with only ints and if it worked > out resend the series. I have reworked code in 2/4 but kept Wolfram as > the author and added my SoB, hope this is OK. > > Reworking the formulas involved moving from s64 to int as the data type > used to store coefficients used in binary scaled fixed point > calculations. By examining the largest values which could be produced in > these calculations a shift of 7 is the maximum scaling which is > possible and still fit inside an int, previously with s64 the decimal scaling > was 1000. > > Changing the decimal scaling also reduces the accuracy of the > calculations. In my tests this was hardly noticeable as the granularity > of the reported temperature to user-space is 0.5C, comparing the value > reported in the s64 vs int implementation only differ very slightly when > it rounded the value to the next 0.5C level. > > However the formulas used to calculate the coefficients are not > documented and none obvious (at lest not to me) so given different > initial values to calculate the coefficients the error might become > larger. Therefore I would like to ask Morimoto-san and/or Khiem to > provide or proxy testing of this less accurate formula and feedback if > it's OK, let me know if there is anything I can do to help out. Tested on H3 and M3-W. The temperatures I get when plugging the fan on/off are very very similar to previous versions of this driver. Thus: Tested-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
