[PATCH v5] thermal: rockchip: make temperature reporting much more accurate

[Caesar Wang]

在 2015年01月25日 09:58, Daniel Kurtz 写道:
> On Fri, Jan 23, 2015 at 11:49 PM, Caesar Wang <wxt at rock-chips.com> 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 at rock-chips.com>
>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
>>
>> ---
>>
>> Changes in v5:
>> Fixed some style.
>>
>> Changes in v4:
>> "return -EAGAIN" instead of "return rk_tsadcv2_code_to_temp(code)"
>>
>> 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 at gmail.com>
>>
>>   drivers/thermal/rockchip_thermal.c | 38 +++++++++++++++++++++++++-------------
>>   1 file changed, 25 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
>> index 1bcddfc..83bdf82 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;
>> -
>> -       if (code > v2_code_table[low].code || code < v2_code_table[high].code)
>> -               return 125000; /* No code available, return max temperature */
>> +       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;
>> +
>> +       /* Invalid code, return -EAGAIN */
>> +       if (code > TSADCV2_DATA_MASK)
>> +               return -EAGAIN;
>>
>> -       while (low <= high) {
>> -               if (code >= v2_code_table[mid].code && code <
>> -                   v2_code_table[mid - 1].code)
>> -                       return v2_code_table[mid].temp;
>> +       while (low <= high && mid) {
>> +               if (code >= v2_code_table[mid].code &&
>> +                   code < v2_code_table[mid - 1].code)
>> +                       break;
>> +               else if (code == TSADCV2_DATA_MASK)
>> +                       break;
> I don't think you need this check since this is v2_code_table[0].
> But, it doesn't hurt, so either way, this is:
>
> Reviewed-by: Daniel Kurtz <djkurtz at chromium.org>
Fixed, Thanks.
>>                  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
>>
>>
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