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thermal: rockchip: make temperature reporting much more accurate 

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

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
This commit is contained in:
Caesar Wang 2015-01-25 10:11:11 +08:00 committed by Eduardo Valentin
parent 1fd2273f96
commit 1e9a1aea7a
1 changed files with 22 additions and 12 deletions
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34
drivers/thermal/rockchip_thermal.c
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@ -193,19 +193,20 @@ static u32 rk_tsadcv2_temp_to_code(long temp)
static long rk_tsadcv2_code_to_temp(u32 code)
{
int high, low, mid;
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;
low = 0;
high = ARRAY_SIZE(v2_code_table) - 1;
mid = (high + low) / 2;
/* Invalid code, return -EAGAIN */
if (code > TSADCV2_DATA_MASK)
return -EAGAIN;
if (code > v2_code_table[low].code || code < v2_code_table[high].code)
return 125000; /* No code available, return max temperature */
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 < v2_code_table[mid].code)
low = mid + 1;
else
@ -213,7 +214,16 @@ 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);
}
/**