ath9k: Program the RTC registers correctly

This patch programs the RTC registers of AR9100 chipsets
correctly during chip reset.

Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath9k/hw.c b/drivers/net/wireless/ath9k/hw.c
index e33c53f..1c02358 100644
--- a/drivers/net/wireless/ath9k/hw.c
+++ b/drivers/net/wireless/ath9k/hw.c
@@ -1482,6 +1482,14 @@
 	u32 rst_flags;
 	u32 tmpReg;
 
+	if (AR_SREV_9100(ah)) {
+		u32 val = REG_READ(ah, AR_RTC_DERIVED_CLK);
+		val &= ~AR_RTC_DERIVED_CLK_PERIOD;
+		val |= SM(1, AR_RTC_DERIVED_CLK_PERIOD);
+		REG_WRITE(ah, AR_RTC_DERIVED_CLK, val);
+		(void)REG_READ(ah, AR_RTC_DERIVED_CLK);
+	}
+
 	REG_WRITE(ah, AR_RTC_FORCE_WAKE, AR_RTC_FORCE_WAKE_EN |
 		  AR_RTC_FORCE_WAKE_ON_INT);