ath9k_hw: avoid possible infinite loop in ar9003_get_pll_sqsum_dvc

commit f18e3c6b67f448ec47b3a5b242789bd3d5644879 upstream.

"ath9k: Fix softlockup in AR9485" with commit id
64bc1239c790e051ff677e023435d770d2ffa174 fixed the reported
issue, yet its better to avoid the possible infinite loop
in ar9003_get_pll_sqsum_dvc by having a timeout as suggested
by ath9k maintainers.
http://www.spinics.net/lists/linux-wireless/msg92126.html.
Based on my testing PLL's locking measurement is done in
~200us (2 iterations).

Cc: Rolf Offermanns <rolf.offermanns@gmx.net>
Cc: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Cc: Senthil Balasubramanian <senthilb@qca.qualcomm.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index 7c2f06ed7a1..05320b9888b 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -682,13 +682,25 @@ static void ath9k_hw_init_qos(struct ath_hw *ah)
 
 u32 ar9003_get_pll_sqsum_dvc(struct ath_hw *ah)
 {
+        struct ath_common *common = ath9k_hw_common(ah);
+        int i = 0;
+
         REG_CLR_BIT(ah, PLL3, PLL3_DO_MEAS_MASK);
         udelay(100);
         REG_SET_BIT(ah, PLL3, PLL3_DO_MEAS_MASK);
 
-        while ((REG_READ(ah, PLL4) & PLL4_MEAS_DONE) == 0)
+        while ((REG_READ(ah, PLL4) & PLL4_MEAS_DONE) == 0) {
+
                 udelay(100);
 
+                if (WARN_ON_ONCE(i >= 100)) {
+                        ath_err(common, "PLL4 meaurement not done\n");
+                        break;
+                }
+
+                i++;
+        }
+
         return (REG_READ(ah, PLL3) & SQSUM_DVC_MASK) >> 3;
 }
 EXPORT_SYMBOL(ar9003_get_pll_sqsum_dvc);