ath9k_hw: Add helper function for interpolation

Also round off interpolated values this would improve power
accuracy by 0.5dB in some cases.

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c b/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
index 5ffeda25bf14e1f86b32d952994eff8dfff09040..1b4e99167b6c1fccb6ff74b5ebfd751863e10f28 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
@@ -2982,6 +2982,16 @@ static int ath9k_hw_ar9300_check_eeprom(struct ath_hw *ah)
        return 0;
 }
 
+static int interpolate(int x, int xa, int xb, int ya, int yb)
+{
+       int bf, factor, plus;
+
+       bf = 2 * (yb - ya) * (x - xa) / (xb - xa);
+       factor = bf / 2;
+       plus = bf % 2;
+       return ya + factor + plus;
+}
+
 static u32 ath9k_hw_ar9300_get_eeprom(struct ath_hw *ah,
                                      enum eeprom_param param)
 {
@@ -3614,7 +3624,7 @@ static int ar9003_hw_power_interpolate(int32_t x,
                        if (hx == lx)
                                y = ly;
                        else    /* interpolate  */
-                               y = ly + (((x - lx) * (hy - ly)) / (hx - lx));
+                               y = interpolate(x, lx, hx, ly, hy);
                } else          /* only low is good, use it */
                        y = ly;
        } else if (hhave)       /* only high is good, use it */
@@ -4204,25 +4214,23 @@ static int ar9003_hw_calibration_apply(struct ath_hw *ah, int frequency)
                        /* so is the high frequency, interpolate */
                        if (hfrequency[ichain] - frequency < 1000) {
 
-                               correction[ichain] = lcorrection[ichain] +
-                                   (((frequency - lfrequency[ichain]) *
-                                     (hcorrection[ichain] -
-                                      lcorrection[ichain])) /
-                                    (hfrequency[ichain] - lfrequency[ichain]));
-
-                               temperature[ichain] = ltemperature[ichain] +
-                                   (((frequency - lfrequency[ichain]) *
-                                     (htemperature[ichain] -
-                                      ltemperature[ichain])) /
-                                    (hfrequency[ichain] - lfrequency[ichain]));
-
-                               voltage[ichain] =
-                                   lvoltage[ichain] +
-                                   (((frequency -
-                                      lfrequency[ichain]) * (hvoltage[ichain] -
-                                                             lvoltage[ichain]))
-                                    / (hfrequency[ichain] -
-                                       lfrequency[ichain]));
+                               correction[ichain] = interpolate(frequency,
+                                               lfrequency[ichain],
+                                               hfrequency[ichain],
+                                               lcorrection[ichain],
+                                               hcorrection[ichain]);
+
+                               temperature[ichain] = interpolate(frequency,
+                                               lfrequency[ichain],
+                                               hfrequency[ichain],
+                                               ltemperature[ichain],
+                                               htemperature[ichain]);
+
+                               voltage[ichain] = interpolate(frequency,
+                                               lfrequency[ichain],
+                                               hfrequency[ichain],
+                                               lvoltage[ichain],
+                                               hvoltage[ichain]);
                        }
                        /* only low is good, use it */
                        else {