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

? 2015?01?22? 12:25, Daniel Kurtz ??:

On Thu, Jan 22, 2015 at 12:21 PM, Caesar Wang
[off-list ref] wrote:

quoted

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

quoted

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.

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.

Maybe "return -EAGAIN"

quoted

quoted

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

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