ath9k: Add Calibration checks

* Prevent divide-by-zero errors in IQ Calibration.
* Do not run temperature compensation if initPDADC or currPDADC is zero.
* Also, introduce a separate function for handling OLC for AR9287.
Signed-off-by: Vivek Natarajan <vnatarajan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/calib.c

@@ -403,7 +403,8 @@ static void ath9k_hw_iqcalibrate(struct ath_hw *ah, u8 numChains)
 		iCoffDenom = (powerMeasI / 2 + powerMeasQ / 2) / 128;
 		qCoffDenom = powerMeasQ / 64;
 
-		if (powerMeasQ != 0) {
+		if ((powerMeasQ != 0) && (iCoffDenom != 0) &&
+		    (qCoffDenom != 0)) {
 			iCoff = iqCorrMeas / iCoffDenom;
 			qCoff = powerMeasI / qCoffDenom - 64;
 			ath_print(common, ATH_DBG_CALIBRATE,
@@ -746,29 +747,48 @@ s16 ath9k_hw_getchan_noise(struct ath_hw *ah, struct ath9k_channel *chan)
 	return nf;
 }
 
-static void ath9k_olc_temp_compensation(struct ath_hw *ah)
+static void ath9k_olc_temp_compensation_9287(struct ath_hw *ah)
 {
-	u32 rddata, i;
-	int delta, currPDADC, regval, slope;
+	u32 rddata;
+	int32_t delta, currPDADC, slope;
 
 	rddata = REG_READ(ah, AR_PHY_TX_PWRCTRL4);
 	currPDADC = MS(rddata, AR_PHY_TX_PWRCTRL_PD_AVG_OUT);
 
-
-	if (OLC_FOR_AR9287_10_LATER) {
 	if (ah->initPDADC == 0 || currPDADC == 0) {
+		/*
+		 * Zero value indicates that no frames have been transmitted yet,
+		 * can't do temperature compensation until frames are transmitted.
+		 */
 		return;
 	} else {
 		slope = ah->eep_ops->get_eeprom(ah, EEP_TEMPSENSE_SLOPE);
-			if (slope == 0)
+
+		if (slope == 0) { /* to avoid divide by zero case */
 			delta = 0;
-			else
+		} else {
 			delta = ((currPDADC - ah->initPDADC)*4) / slope;
+		}
 		REG_RMW_FIELD(ah, AR_PHY_CH0_TX_PWRCTRL11,
 			      AR_PHY_TX_PWRCTRL_OLPC_TEMP_COMP, delta);
 		REG_RMW_FIELD(ah, AR_PHY_CH1_TX_PWRCTRL11,
 			      AR_PHY_TX_PWRCTRL_OLPC_TEMP_COMP, delta);
 	}
+}
+
+static void ath9k_olc_temp_compensation(struct ath_hw *ah)
+{
+	u32 rddata, i;
+	int delta, currPDADC, regval;
+
+	if (OLC_FOR_AR9287_10_LATER) {
+		ath9k_olc_temp_compensation_9287(ah);
+	} else {
+		rddata = REG_READ(ah, AR_PHY_TX_PWRCTRL4);
+		currPDADC = MS(rddata, AR_PHY_TX_PWRCTRL_PD_AVG_OUT);
+
+		if (ah->initPDADC == 0 || currPDADC == 0) {
+			return;
 		} else {
 			if (ah->eep_ops->get_eeprom(ah, EEP_DAC_HPWR_5G))
 				delta = (currPDADC - ah->initPDADC + 4) / 8;
@@ -782,11 +802,13 @@ static void ath9k_olc_temp_compensation(struct ath_hw *ah)
 					if (regval < 0)
 						regval = 0;
 
-				REG_RMW_FIELD(ah, AR_PHY_TX_GAIN_TBL1 + i * 4,
+					REG_RMW_FIELD(ah,
+						      AR_PHY_TX_GAIN_TBL1 + i * 4,
 						      AR_PHY_TX_GAIN, regval);
 				}
 			}
 		}
+	}
 }
 
 static void ath9k_hw_9271_pa_cal(struct ath_hw *ah)