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Diffstat (limited to 'drivers/net/wireless/ath/ath5k/pcu.c')
-rw-r--r--drivers/net/wireless/ath/ath5k/pcu.c31
1 files changed, 29 insertions, 2 deletions
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index 174412f..5212e27 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -496,6 +496,8 @@ void ath5k_hw_set_rx_filter(struct ath5k_hw *ah, u32 filter)
* Beacon control *
\****************/
+#define ATH5K_MAX_TSF_READ 10
+
/**
* ath5k_hw_get_tsf64 - Get the full 64bit TSF
*
@@ -505,10 +507,35 @@ void ath5k_hw_set_rx_filter(struct ath5k_hw *ah, u32 filter)
*/
u64 ath5k_hw_get_tsf64(struct ath5k_hw *ah)
{
- u64 tsf = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+ u32 tsf_lower, tsf_upper1, tsf_upper2;
+ int i;
+
+ /*
+ * While reading TSF upper and then lower part, the clock is still
+ * counting (or jumping in case of IBSS merge) so we might get
+ * inconsistent values. To avoid this, we read the upper part again
+ * and check it has not been changed. We make the hypothesis that a
+ * maximum of 3 changes can happens in a row (we use 10 as a safe
+ * value).
+ *
+ * Impact on performance is pretty small, since in most cases, only
+ * 3 register reads are needed.
+ */
+
+ tsf_upper1 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+ for (i = 0; i < ATH5K_MAX_TSF_READ; i++) {
+ tsf_lower = ath5k_hw_reg_read(ah, AR5K_TSF_L32);
+ tsf_upper2 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
+ if (tsf_upper2 == tsf_upper1)
+ break;
+ tsf_upper1 = tsf_upper2;
+ }
+
+ WARN_ON( i == ATH5K_MAX_TSF_READ );
+
ATH5K_TRACE(ah->ah_sc);
- return ath5k_hw_reg_read(ah, AR5K_TSF_L32) | (tsf << 32);
+ return (((u64)tsf_upper1 << 32) | tsf_lower);
}
/**
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