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| author | Bob Copeland <me@bobcopeland.com> | 2010-01-16 14:36:52 -0500 |
|---|---|---|
| committer | John W. Linville <linville@tuxdriver.com> | 2010-01-18 15:07:02 -0500 |
| commit | e850f68b8f27a76c4377c34f2e216b8e7e10db3d (patch) | |
| tree | 0b2a6ffb15ede031c149d8c37a5ba359bb5695f8 /net/mac80211/rc80211_pid_algo.c | |
| parent | bb5d2db5709e469f4a8c01eaaee9a275ed9772aa (diff) | |
| download | lwn-e850f68b8f27a76c4377c34f2e216b8e7e10db3d.tar.gz lwn-e850f68b8f27a76c4377c34f2e216b8e7e10db3d.zip | |
mac80211: fix sign error in pid controller
While testing the pid rate controller in mac80211_hwsim, I noticed
that once the controller reached 54 Mbit rates, it would fail to
lower the rate when necessary. The debug log shows:
1945 186786 pf_sample 50 3534 3577 50
My interpretation is that the fixed point scaling of the target
error value (pf) is incorrect: the error value of 50 compared to
a target of 14 case should result in a scaling value of
(14-50) = -36 * 256 or -9216, but instead it is (14 * 256)-50, or
3534.
Correct this by doing fixed point scaling after subtraction.
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Acked-by: Stefano Brivio <stefano.brivio@polimi.it>
Acked-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'net/mac80211/rc80211_pid_algo.c')
| -rw-r--r-- | net/mac80211/rc80211_pid_algo.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/mac80211/rc80211_pid_algo.c b/net/mac80211/rc80211_pid_algo.c index 699d3ed869c4..29bc4c516238 100644 --- a/net/mac80211/rc80211_pid_algo.c +++ b/net/mac80211/rc80211_pid_algo.c @@ -190,7 +190,7 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo, rate_control_pid_normalize(pinfo, sband->n_bitrates); /* Compute the proportional, integral and derivative errors. */ - err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf; + err_prop = (pinfo->target - pf) << RC_PID_ARITH_SHIFT; err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift; spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop; |