Commit 1dc4d1e6 authored by Stefano Brivio's avatar Stefano Brivio Committed by David S. Miller
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rc80211-pid: add sharpening factor



This patch introduces a PID sharpening factor for faster response after
association and low activity events.
Signed-off-by: default avatarStefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: default avatarMattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 90d501d6
...@@ -23,13 +23,16 @@ ...@@ -23,13 +23,16 @@
* *
* The controller basically computes the following: * The controller basically computes the following:
* *
* adj = CP * err + CI * err_avg + CD * (err - last_err) * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
* *
* where * where
* adj adjustment value that is used to switch TX rate (see below) * adj adjustment value that is used to switch TX rate (see below)
* err current error: target vs. current failed frames percentage * err current error: target vs. current failed frames percentage
* last_err last error * last_err last error
* err_avg average (i.e. poor man's integral) of recent errors * err_avg average (i.e. poor man's integral) of recent errors
* sharpening non-zero when fast response is needed (i.e. right after
* association or no frames sent for a long time), heading
* to zero over time
* CP Proportional coefficient * CP Proportional coefficient
* CI Integral coefficient * CI Integral coefficient
* CD Derivative coefficient * CD Derivative coefficient
...@@ -65,6 +68,10 @@ ...@@ -65,6 +68,10 @@
#define RC_PID_SMOOTHING_SHIFT 3 #define RC_PID_SMOOTHING_SHIFT 3
#define RC_PID_SMOOTHING (1 << RC_PID_SMOOTHING_SHIFT) #define RC_PID_SMOOTHING (1 << RC_PID_SMOOTHING_SHIFT)
/* Sharpening factor (used for D part of PID controller) */
#define RC_PID_SHARPENING_FACTOR 0
#define RC_PID_SHARPENING_DURATION 0
/* Fixed point arithmetic shifting amount. */ /* Fixed point arithmetic shifting amount. */
#define RC_PID_ARITH_SHIFT 8 #define RC_PID_ARITH_SHIFT 8
...@@ -131,8 +138,11 @@ struct rc_pid_sta_info { ...@@ -131,8 +138,11 @@ struct rc_pid_sta_info {
*/ */
s32 err_avg_sc; s32 err_avg_sc;
/* Last framed failes percentage sample */ /* Last framed failes percentage sample. */
u32 last_pf; u32 last_pf;
/* Sharpening needed. */
u8 sharp_cnt;
}; };
/* Algorithm parameters. We keep them on a per-algorithm approach, so they can /* Algorithm parameters. We keep them on a per-algorithm approach, so they can
...@@ -267,20 +277,26 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo, ...@@ -267,20 +277,26 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo,
mode = local->oper_hw_mode; mode = local->oper_hw_mode;
spinfo = sta->rate_ctrl_priv; spinfo = sta->rate_ctrl_priv;
/* In case nothing happened during the previous control interval, turn
* the sharpening factor on. */
if (jiffies - spinfo->last_sample > 2 * RC_PID_INTERVAL)
spinfo->sharp_cnt = RC_PID_SHARPENING_DURATION;
spinfo->last_sample = jiffies; spinfo->last_sample = jiffies;
/* If no frames were transmitted, we assume the old sample is /* This should never happen, but in case, we assume the old sample is
* still a good measurement and copy it. */ * still a good measurement and copy it. */
if (spinfo->tx_num_xmit == 0) if (unlikely(spinfo->tx_num_xmit == 0))
pf = spinfo->last_pf; pf = spinfo->last_pf;
else { else {
pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit; pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
pf <<= RC_PID_ARITH_SHIFT; pf <<= RC_PID_ARITH_SHIFT;
spinfo->tx_num_xmit = 0;
spinfo->tx_num_failed = 0;
} }
spinfo->tx_num_xmit = 0;
spinfo->tx_num_failed = 0;
/* If we just switched rate, update the rate behaviour info. */ /* If we just switched rate, update the rate behaviour info. */
if (pinfo->oldrate != sta->txrate) { if (pinfo->oldrate != sta->txrate) {
...@@ -302,8 +318,11 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo, ...@@ -302,8 +318,11 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo,
spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop; spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
err_int = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT; err_int = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
err_der = pf - spinfo->last_pf; err_der = pf - spinfo->last_pf
* (1 + RC_PID_SHARPENING_FACTOR * spinfo->sharp_cnt);
spinfo->last_pf = pf; spinfo->last_pf = pf;
if (spinfo->sharp_cnt)
spinfo->sharp_cnt--;
/* Compute the controller output. */ /* Compute the controller output. */
adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
......
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