ar9170: handle overflow in tsf_low register during get_tsf

ar9170_op_get_tsf: handle a carry from TSF_L into TSF_H
by reading TSF_H twice.
Signed-off-by: Joerg Albert <jal2@gmx.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ar9170/cmd.c

@@ -72,8 +72,7 @@ int ar9170_write_reg(struct ar9170 *ar, const u32 reg, const u32 val)
 	return err;
 }
 
-static int ar9170_read_mreg(struct ar9170 *ar, int nregs,
-			    const u32 *regs, u32 *out)
+int ar9170_read_mreg(struct ar9170 *ar, int nregs, const u32 *regs, u32 *out)
 {
 	int i, err;
 	__le32 *offs, *res;

drivers/net/wireless/ath/ar9170/cmd.h

@@ -44,6 +44,7 @@
 int ar9170_write_mem(struct ar9170 *ar, const __le32 *data, size_t len);
 int ar9170_write_reg(struct ar9170 *ar, const u32 reg, const u32 val);
 int ar9170_read_reg(struct ar9170 *ar, u32 reg, u32 *val);
+int ar9170_read_mreg(struct ar9170 *ar, int nregs, const u32 *regs, u32 *out);
 int ar9170_echo_test(struct ar9170 *ar, u32 v);
 
 /*

drivers/net/wireless/ath/ar9170/main.c

@@ -2192,22 +2192,30 @@ static u64 ar9170_op_get_tsf(struct ieee80211_hw *hw)
 {
 	struct ar9170 *ar = hw->priv;
 	int err;
-	u32 tsf_low;
-	u32 tsf_high;
 	u64 tsf;
+#define NR 3
+	static const u32 addr[NR] = { AR9170_MAC_REG_TSF_H,
+				    AR9170_MAC_REG_TSF_L,
+				    AR9170_MAC_REG_TSF_H };
+	u32 val[NR];
+	int loops = 0;
 
 	mutex_lock(&ar->mutex);
-	err = ar9170_read_reg(ar, AR9170_MAC_REG_TSF_L, &tsf_low);
-	if (!err)
-		err = ar9170_read_reg(ar, AR9170_MAC_REG_TSF_H, &tsf_high);
+
+	while (loops++ < 10) {
+		err = ar9170_read_mreg(ar, NR, addr, val);
+		if (err || val[0] == val[2])
+			break;
+	}
+
 	mutex_unlock(&ar->mutex);
 
 	if (WARN_ON(err))
 		return 0;
-
-	tsf = tsf_high;
-	tsf = (tsf << 32) | tsf_low;
+	tsf = val[0];
+	tsf = (tsf << 32) | val[1];
 	return tsf;
+#undef NR
 }
 
 static int ar9170_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,