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

? 2015?01?22? 12:01, Daniel Kurtz ??:

On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang [off-list ref] wrote:

quoted

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 <redacted>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

---

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@gmail.com>

  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.

quoted

         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 (???)
???????????
Fuzhou Rockchip Electronics Co.Ltd
?????????????89????A?18??(350003)
Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou, Fujian,PRC
Email:wxt at rock-chips.com
Tel:+86-591-83991906/07->8221