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AAH: Fix PID gain for HW clock recovery.

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Before HW came in, when doing SW clock recovery, gain had been set to
produce a correction expressed in PPM from [-100, 100] PPM.  The HW
local clock HAL has been spec'ed to take a drive range from MIN_INT_16
to MAX_INT_16.  This changes the PID recovery loop to use a range from
MIN_INT_16 to MAX_INT_16, and adjusts the P and I gains to be the same
as they were before, but adjusted for the scale change.

Change-Id: I531175e5fbb20b7ba6ee06f457c5f4ad12c123ff
This commit is contained in:
John Grossman
2011-10-13 16:03:56 -07:00
parent 4367e2c967
commit 39722542b9
1 changed files with 25 additions and 14 deletions
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39
services/aah_timesrv/clock_recovery.cpp
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@@ -240,7 +240,7 @@ bool ClockRecoveryLoop::pushDisciplineEvent(int64_t local_time,
}
LOGV("rtt %lld observed %lld nominal %lld delta = %5lld "
"int = %7d correction %3d (P %3d, I %3d, D %3d)\n",
"int = %7d correction %5d (P %5d, I %5d, D %5d)\n",
filter_data_[min_rtt].rtt,
observed_common,
nominal_common_time,
@@ -270,20 +270,20 @@ void ClockRecoveryLoop::computePIDParams() {
// level in case they have a HW clock discipline solution with parameters
// tuned specifically for it.
// Correction factor is limited to +/-100 PPM.
pid_params_.correction_min = -100;
pid_params_.correction_max = 100;
// Correction factor is limited to MIN/MAX_INT_16
pid_params_.correction_min = -0x8000;
pid_params_.correction_max = 0x7FFF;
// Default proportional gain to 1:10. (1 PPM of correction for
// every 10 uSec of instantaneous error)
// Default proportional gain to 2^15:1000. (max proportional drive at 1mSec
// of instantaneous error)
memset(&pid_params_.gain_P, 0, sizeof(pid_params_.gain_P));
pid_params_.gain_P.a_to_b_numer = 1;
pid_params_.gain_P.a_to_b_denom = 10;
pid_params_.gain_P.a_to_b_numer = 0x8000;
pid_params_.gain_P.a_to_b_denom = 1000;
// Set the integral gain to 1:50
// Set the integral gain to 2^15:5000
memset(&pid_params_.gain_I, 0, sizeof(pid_params_.gain_I));
pid_params_.gain_I.a_to_b_numer = 1;
pid_params_.gain_I.a_to_b_denom = 50;
pid_params_.gain_I.a_to_b_numer = 0x8000;
pid_params_.gain_I.a_to_b_denom = 5000;
// Default controller is just a PI controller. Right now, the network based
// measurements of the error are way to noisy to feed into the differential
@@ -352,10 +352,21 @@ int32_t ClockRecoveryLoop::doGainScale(const LinearTransform& gain,
}
void ClockRecoveryLoop::applySlew() {
if (local_clock_can_slew_)
if (local_clock_can_slew_) {
local_clock_->setLocalSlew(correction_cur_);
else
common_clock_->setSlew(local_clock_->getLocalTime(), correction_cur_);
} else {
// The SW clock recovery implemented by the common clock class expects
// values expressed in PPM. Map the MIN/MAX_INT_16 drive range to +/-
// 100ppm.
int sw_correction;
sw_correction = correction_cur_ - pid_params_.correction_min;
sw_correction *= 200;
sw_correction /= (pid_params_.correction_max -
pid_params_.correction_min);
sw_correction -= 100;
common_clock_->setSlew(local_clock_->getLocalTime(), sw_correction);
}
}
} // namespace android