Re: [PATCH v3] thermal: rockchip: make temperature reporting much more accurate

[Daniel Kurtz]

On Thu, Jan 22, 2015 at 12:21 PM, Caesar Wang
<caesar.wang@xxxxxxxxxxxxxx> wrote:
>
> å 2015å01æ22æ 12:01, Daniel Kurtz åé:
>
>> On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang <wxt@xxxxxxxxxxxxxx> wrote:
>>>
>>> In general, the kernel should report temperature readings exactly as
>>> reported by the hardware. The cpu / gpu thermal driver works in 5 degree
>>> increments,but we ought to do more accurate. The temperature will do
>>> linear interpolation between the entries in the table.
>>>
>>> Test= $md5sum /dev/zero &
>>> $while true; do grep "" /sys/class/thermal/thermal_zone[1-2]/temp;
>>> sleep .5; done
>>>
>>> e.g. We can get the result as follows:
>>>      /sys/class/thermal/thermal_zone1/temp:39994
>>>      /sys/class/thermal/thermal_zone2/temp:39086
>>>      /sys/class/thermal/thermal_zone1/temp:39994
>>>      /sys/class/thermal/thermal_zone2/temp:39540
>>>      /sys/class/thermal/thermal_zone1/temp:39540
>>>      /sys/class/thermal/thermal_zone2/temp:39540
>>>      /sys/class/thermal/thermal_zone1/temp:39540
>>>      /sys/class/thermal/thermal_zone2/temp:39994
>>>
>>> Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx>
>>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
>>>
>>> ---
>>>
>>> Changes in v3:
>>> Suggested-by Daniel Kurtz,
>>> the check doesn't reject "code == 0xfff"
>>> Fixed in rk_tsadcv2_code_to_temp(u32 code)
>>>
>>> Changes in v2:
>>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
>>>
>>>   drivers/thermal/rockchip_thermal.c | 32
>>> ++++++++++++++++++++++----------
>>>   1 file changed, 22 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/thermal/rockchip_thermal.c
>>> b/drivers/thermal/rockchip_thermal.c
>>> index 1bcddfc..ce18007 100644
>>> --- a/drivers/thermal/rockchip_thermal.c
>>> +++ b/drivers/thermal/rockchip_thermal.c
>>> @@ -193,19 +193,22 @@ static u32 rk_tsadcv2_temp_to_code(long temp)
>>>
>>>   static long rk_tsadcv2_code_to_temp(u32 code)
>>>   {
>>> -       int high, low, mid;
>>> -
>>> -       low = 0;
>>> -       high = ARRAY_SIZE(v2_code_table) - 1;
>>> -       mid = (high + low) / 2;
>>> +       unsigned int low = 0;
>>> +       unsigned int high = ARRAY_SIZE(v2_code_table) - 1;
>>> +       unsigned int mid = (low + high) / 2;
>>> +       unsigned int num;
>>> +       unsigned long denom;
>>>
>>> +       /* No code available, return callback */
>>>          if (code > v2_code_table[low].code || code <
>>> v2_code_table[high].code)
>>> -               return 125000; /* No code available, return max
>>> temperature */
>>> +               return rk_tsadcv2_code_to_temp(code);
>>
>> Isn't this an infinite recursion?
>
>
> No, I think we can try check if it  is happened.
> Maybe we can return a warning/error for it.

I mean, if the 'if' condition is true, then this will just call the
same function again with the same code, and again, and again...
Just return an error code here, -ENOENT maybe?
I am not sure what error code is appropriate.


>
>>>          while (low <= high) {
>>> -               if (code >= v2_code_table[mid].code && code <
>>> -                   v2_code_table[mid - 1].code)
>>> -                       return v2_code_table[mid].temp;
>>> +               if (code >= v2_code_table[mid].code &&
>>> +                   code < v2_code_table[mid - 1].code)
>>> +                       break;
>>> +               else if (code == TSADCV2_DATA_MASK)
>>> +                       break;
>>>                  else if (code < v2_code_table[mid].code)
>>>                          low = mid + 1;
>>>                  else
>>> @@ -213,7 +216,16 @@ static long rk_tsadcv2_code_to_temp(u32 code)
>>>                  mid = (low + high) / 2;
>>>          }
>>>
>>> -       return 125000;
>>> +       /*
>>> +        * The 5C granularity provided by the table is too much. Let's
>>> +        * assume that the relationship between sensor readings and
>>> +        * temperature between 2 table entries is linear and interpolate
>>> +        * to produce less granular result.
>>> +        */
>>> +       num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp;
>>> +       num *= v2_code_table[mid - 1].code - code;
>>> +       denom = v2_code_table[mid - 1].code - v2_code_table[mid].code;
>>> +       return v2_code_table[mid - 1].temp + (num / denom);
>>>   }
>>>
>>>   /**
>>> --
>>> 1.9.1
>>>
>>>
>>
>>
>
> --
> Best regards
> Caesar Wang (çæè)
> çåçèåçåæéåå
> Fuzhou Rockchip Electronics Co.Ltd
> çåççååéçèèäåé89åèäåAå18åæ(350003)
> Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou,
> Fujian,PRC
> Email:wxt@xxxxxxxxxxxxxx
> Tel:+86-591-83991906/07->8221
>
>
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