Merge git://git.infradead.org/battery-2.6

[cascardo/linux.git] / kernel / time / ntp.c

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index c631168..d232189 100644 (file)
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -149,10 +149,18 @@ static void ntp_update_offset(long offset)
        time_reftime = get_seconds();
 
        offset64    = offset;
-       freq_adj    = (offset64 * secs) <<
-                       (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
+       freq_adj    = ntp_update_offset_fll(offset64, secs);
 
-       freq_adj    += ntp_update_offset_fll(offset64, secs);
+       /*
+        * Clamp update interval to reduce PLL gain with low
+        * sampling rate (e.g. intermittent network connection)
+        * to avoid instability.
+        */
+       if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
+               secs = 1 << (SHIFT_PLL + 1 + time_constant);
+
+       freq_adj    += (offset64 * secs) <<
+                       (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 
        freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);