[PATCH 4/5] thermal: rockchip: optimize the conversion table

[Caesar Wang]

In order to support the valid temperature can conver to analog value.
The rockchip thermal has not supported the all valid temperature.

For example:
In some cases, we need adjust the trip point.
$cd /sys/class/thermal/thermal_zone*
echo 68000 > trip_point_0_temp
That will report the error message before posting this patch.

Signed-off-by: Caesar Wang <w...@rock-chips.com>
---

 drivers/thermal/rockchip_thermal.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/thermal/rockchip_thermal.c 
b/drivers/thermal/rockchip_thermal.c
index 535f1fa..f4d4be9 100644
--- a/drivers/thermal/rockchip_thermal.c
+++ b/drivers/thermal/rockchip_thermal.c
@@ -401,6 +401,8 @@ static u32 rk_tsadcv2_temp_to_code(const struct 
chip_tsadc_table *table,
                                   int temp)
 {
        int high, low, mid;
+       unsigned long num;
+       unsigned int denom;
        u32 error = table->data_mask;
 
        low = 0;
@@ -421,6 +423,27 @@ static u32 rk_tsadcv2_temp_to_code(const struct 
chip_tsadc_table *table,
                mid = (low + high) / 2;
        }
 
+       /*
+        * The conversion code granularity provided by the table. Let's
+        * assume that the relationship between temperature and
+        * analog value between 2 table entries is linear and interpolate
+        * to produce less granular result.
+        */
+       num = abs(table->id[mid].code - table->id[mid + 1].code);
+       num *= temp - table->id[mid].temp;
+       denom = table->id[mid + 1].temp - table->id[mid].temp;
+
+       switch (table->mode) {
+       case ADC_DECREMENT:
+               return table->id[mid].code - (num / denom);
+       case ADC_INCREMENT:
+               return table->id[mid].code + (num / denom);
+       default:
+               pr_err("%s: invalid conversion table, mode=%d\n",
+                      __func__, table->mode);
+               return error;
+       }
+
 exit:
        pr_err("%s: invalid temperature, temp=%d error=%d\n",
               __func__, temp, error);
-- 
2.7.4