ltr301als: Change the adc-lux conversion method

BZ: 39399 41574

The adc-lux conversion is not accurate on the DV20, change the
algorithm and coefficent according to the vendor's advice.

Change-Id: I5a6e11c86c8553cd40732c9cf300421a69ac440b
Signed-off-by: Leo Yan <leo.yan@intel.com>
Reviewed-on: http://android.intel.com:8080/52892
Reviewed-by: Liu, Hong <hong.liu@intel.com>
Reviewed-by: Chen, Jie D <jie.d.chen@intel.com>
Reviewed-by: Du, Alek <alek.du@intel.com>
Tested-by: Tang, HaifengX <haifengx.tang@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>

diff --git a/drivers/input/misc/ltr301als.c b/drivers/input/misc/ltr301als.c
index a8b5e3a..9084b7c 100644 (file)
--- a/drivers/input/misc/ltr301als.c
+++ b/drivers/input/misc/ltr301als.c
@@ -79,17 +79,18 @@
 
 /* adc to lux calculation channel coefficients for different ranges */
 #define CH0_COEFF_RANGE0       17743
-#define CH1_COEFF_RANGE0       -11059
+#define CH1_COEFF_RANGE0       11059
 #define CH0_COEFF_RANGE1       37725
-#define CH1_COEFF_RANGE1       13363
-#define CH0_COEFF_RANGE2       16900
-#define CH1_COEFF_RANGE2       1690
-#define CH0_COEFF_RANGE3       16900
-#define CH1_COEFF_RANGE3       -490
+#define CH1_COEFF_RANGE1       -13363
+#define CH0_COEFF_RANGE2       2075
+#define CH1_COEFF_RANGE2       960
 
 #define RATIO_RANGE0           45
-#define RATIO_RANGE1           64
-#define RATIO_RANGE2           85
+#define RATIO_RANGE1           71
+#define RATIO_RANGE2           95
+
+#define WINDOW_COMP            50
+#define COEFF_SCALE            10000
 
 #define IN_THRESHOLD_RANGE     1
 #define LUX_TO_ADC_LOTHRESH    2
@@ -175,6 +176,7 @@ static int ltr301_get_lux(struct ltr301_chip *chip)
        int ratio = 0;
        int ch0_coeff = 0;
        int ch1_coeff = 0;
+       int wc = 0;
 
        ch1 = ltr301_read_word(chip, ALS_DATA_CH1_0);
        if (ch1 < 0)
@@ -190,20 +192,20 @@ static int ltr301_get_lux(struct ltr301_chip *chip)
        if (ratio < RATIO_RANGE0)       {
                ch0_coeff = CH0_COEFF_RANGE0;
                ch1_coeff = CH1_COEFF_RANGE0;
+               wc = WINDOW_COMP;
        } else if (ratio < RATIO_RANGE1) {
                ch0_coeff = CH0_COEFF_RANGE1;
                ch1_coeff = CH1_COEFF_RANGE1;
-       } else if (ratio < RATIO_RANGE2) {
+       } else {
                ch0_coeff = CH0_COEFF_RANGE2;
                ch1_coeff = CH1_COEFF_RANGE2;
-       } else {
-               ch0_coeff = CH0_COEFF_RANGE3;
-               ch1_coeff = CH1_COEFF_RANGE3;
        }
 
        chip->ch0 = ch0;
        /* ch_coeff are x10000, compensate for window loss while scaling down */
-       lux = ((ch0 * ch0_coeff) - (ch1 * ch1_coeff)) / (100 * chip->opacity);
+       lux = (ch0 * ch0_coeff + ch1 * ch1_coeff) * chip->opacity / COEFF_SCALE;
+       if (lux >= wc)
+               lux += wc;
 
        dev_dbg(&chip->client->dev, "%s:ch0=%d, ch1=%d, lux=%d\n",
                                                __func__, ch0, ch1, lux);