sys: introduce generic driver
This driver is intended to complete system-specific drivers that don't have implemented all required driver functionality. Currently, it implements offset functions working on top of system-specific frequency functions. Offsets are corrected by changing frequency, similarly to fast slewing implemented in the Linux driver.
This commit is contained in:
Miroslav Lichvar
parent
4cf8395470
commit
fc235a3f16
3 changed files with 321 additions and 0 deletions
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@ -81,6 +81,7 @@ typedef enum {
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LOGF_Rtc,
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LOGF_Regress,
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LOGF_Sys,
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LOGF_SysGeneric,
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LOGF_SysLinux,
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LOGF_SysNetBSD,
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LOGF_SysSolaris,
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278
sys_generic.c
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278
sys_generic.c
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@ -0,0 +1,278 @@
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/*
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chronyd/chronyc - Programs for keeping computer clocks accurate.
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**********************************************************************
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* Copyright (C) Miroslav Lichvar 2014
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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**********************************************************************
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=======================================================================
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Generic driver functions to complete system-specific drivers
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*/
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#include "config.h"
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#include "sysincl.h"
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#include "sys_generic.h"
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#include "local.h"
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#include "localp.h"
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#include "logging.h"
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#include "sched.h"
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#include "util.h"
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/* ================================================== */
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/* System clock frequency drivers */
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static lcl_ReadFrequencyDriver drv_read_freq;
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static lcl_SetFrequencyDriver drv_set_freq;
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/* Current frequency as requested by the local module (in ppm) */
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static double base_freq;
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/* Maximum frequency that can be set by drv_set_freq (in ppm) */
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static double max_freq;
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/* Maximum expected delay in the actual frequency change (e.g. kernel ticks)
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in local time */
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static double max_freq_change_delay;
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/* Amount of outstanding offset to process */
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static double offset_register;
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/* Minimum offset to correct */
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#define MIN_OFFSET_CORRECTION 1.0e-9
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/* Current frequency offset between base_freq and the real clock frequency
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as set by drv_set_freq (not in ppm) */
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static double slew_freq;
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/* Maximum allowed slewing frequency */
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#define MAX_SLEW_FREQ (1 / 12.0)
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/* Time (raw) of last update of slewing frequency and offset */
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static struct timeval slew_start;
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/* Limits for the slew timeout */
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#define MIN_SLEW_TIMEOUT 1.0
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#define MAX_SLEW_TIMEOUT 1.0e4
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/* Scheduler timeout ID and flag if the timer is currently running */
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static SCH_TimeoutID slew_timeout_id;
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static int slew_timer_running;
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/* Suggested offset correction rate (correction time * offset) */
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static double correction_rate;
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/* Maximum expected offset correction error caused by delayed change in the
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real frequency of the clock */
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static double slew_error;
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/* ================================================== */
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static void handle_end_of_slew(void *anything);
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/* ================================================== */
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/* Adjust slew_start on clock step */
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static void
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handle_step(struct timeval *raw, struct timeval *cooked, double dfreq,
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double doffset, int is_step_change, void *anything)
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{
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if (is_step_change)
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UTI_AddDoubleToTimeval(&slew_start, -doffset, &slew_start);
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}
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/* ================================================== */
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/* End currently running slew and start a new one */
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static void
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update_slew(void)
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{
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struct timeval now, end_of_slew;
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double old_slew_freq, total_freq, corr_freq, duration;
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/* Remove currently running timeout */
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if (slew_timer_running)
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SCH_RemoveTimeout(slew_timeout_id);
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LCL_ReadRawTime(&now);
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/* Adjust the offset register by achieved slew */
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UTI_DiffTimevalsToDouble(&duration, &now, &slew_start);
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offset_register -= slew_freq * duration;
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/* Estimate how long should the next slew take */
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if (fabs(offset_register) < MIN_OFFSET_CORRECTION) {
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duration = MAX_SLEW_TIMEOUT;
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} else {
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duration = correction_rate / fabs(offset_register);
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if (duration < MIN_SLEW_TIMEOUT)
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duration = MIN_SLEW_TIMEOUT;
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}
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/* Get frequency offset needed to slew the offset in the duration
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and clamp it to the allowed maximum */
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corr_freq = offset_register / duration;
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if (corr_freq < -MAX_SLEW_FREQ)
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corr_freq = -MAX_SLEW_FREQ;
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else if (corr_freq > MAX_SLEW_FREQ)
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corr_freq = MAX_SLEW_FREQ;
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/* Get the new real frequency and clamp it */
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total_freq = base_freq + corr_freq * (1.0e6 - base_freq);
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if (total_freq > max_freq)
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total_freq = max_freq;
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else if (total_freq < -max_freq)
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total_freq = -max_freq;
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/* Set the new frequency (the actual frequency returned by the call may be
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slightly different from the requested frequency due to rounding) */
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total_freq = (*drv_set_freq)(total_freq);
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/* Compute the new slewing frequency, it's relative to the real frequency to
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make the calculation in offset_convert() cheaper */
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old_slew_freq = slew_freq;
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slew_freq = (total_freq - base_freq) / (1.0e6 - total_freq);
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/* Compute the dispersion introduced by changing frequency and add it
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to all statistics held at higher levels in the system */
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slew_error = fabs((old_slew_freq - slew_freq) * max_freq_change_delay);
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lcl_InvokeDispersionNotifyHandlers(slew_error);
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/* Compute the duration of the slew and clamp it. If the slewing frequency
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is zero or has wrong sign (e.g. due to rounding in the frequency driver or
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when base_freq is larger than max_freq), use maximum timeout and try again
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on the next update. */
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if (offset_register * slew_freq <= 0.0) {
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duration = MAX_SLEW_TIMEOUT;
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} else {
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duration = offset_register / slew_freq;
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if (duration < MIN_SLEW_TIMEOUT)
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duration = MIN_SLEW_TIMEOUT;
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else if (duration > MAX_SLEW_TIMEOUT)
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duration = MAX_SLEW_TIMEOUT;
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}
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/* Restart timer for the next update */
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UTI_AddDoubleToTimeval(&now, duration, &end_of_slew);
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slew_timeout_id = SCH_AddTimeout(&end_of_slew, handle_end_of_slew, NULL);
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slew_start = now;
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slew_timer_running = 1;
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DEBUG_LOG(LOGF_SysGeneric, "slew offset=%e corr_rate=%e base_freq=%f total_freq=%f slew_freq=%e duration=%f",
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offset_register, correction_rate, base_freq, total_freq, slew_freq, duration);
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}
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/* ================================================== */
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static void
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handle_end_of_slew(void *anything)
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{
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slew_timer_running = 0;
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update_slew();
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}
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/* ================================================== */
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static double
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read_frequency(void)
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{
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return base_freq;
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}
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/* ================================================== */
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static double
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set_frequency(double freq_ppm)
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{
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base_freq = freq_ppm;
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update_slew();
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return base_freq;
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}
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/* ================================================== */
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static void
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accrue_offset(double offset, double corr_rate)
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{
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offset_register += offset;
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correction_rate = corr_rate;
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update_slew();
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}
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/* ================================================== */
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/* Determine the correction to generate the cooked time for given raw time */
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static void
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offset_convert(struct timeval *raw,
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double *corr, double *err)
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{
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double duration;
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UTI_DiffTimevalsToDouble(&duration, raw, &slew_start);
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*corr = slew_freq * duration - offset_register;
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if (err)
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*err = fabs(duration) <= max_freq_change_delay ? slew_error : 0.0;
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}
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/* ================================================== */
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void
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SYS_Generic_CompleteFreqDriver(double max_set_freq_ppm, double max_set_freq_delay,
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lcl_ReadFrequencyDriver sys_read_freq,
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lcl_SetFrequencyDriver sys_set_freq,
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lcl_ApplyStepOffsetDriver sys_apply_step_offset,
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lcl_SetLeapDriver sys_set_leap)
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{
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max_freq = max_set_freq_ppm;
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max_freq_change_delay = max_set_freq_delay * (1.0 + max_freq / 1.0e6);
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drv_read_freq = sys_read_freq;
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drv_set_freq = sys_set_freq;
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base_freq = (*drv_read_freq)();
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slew_freq = 0.0;
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offset_register = 0.0;
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lcl_RegisterSystemDrivers(read_frequency, set_frequency,
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accrue_offset, sys_apply_step_offset,
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offset_convert, sys_set_leap);
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LCL_AddParameterChangeHandler(handle_step, NULL);
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}
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/* ================================================== */
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void
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SYS_Generic_Finalise(void)
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{
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/* Must *NOT* leave a slew running - clock could drift way off
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if the daemon is not restarted */
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if (slew_timer_running) {
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SCH_RemoveTimeout(slew_timeout_id);
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slew_timer_running = 0;
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}
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(*drv_set_freq)(base_freq);
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}
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/* ================================================== */
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42
sys_generic.h
Normal file
42
sys_generic.h
Normal file
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@ -0,0 +1,42 @@
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/*
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chronyd/chronyc - Programs for keeping computer clocks accurate.
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**********************************************************************
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* Copyright (C) Miroslav Lichvar 2014
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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**********************************************************************
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=======================================================================
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Header file for generic driver
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*/
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#ifndef GOT_SYS_GENERIC_H
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#define GOT_SYS_GENERIC_H
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#include "localp.h"
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/* Register a completed driver that implements offset functions on top of
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provided frequency functions */
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extern void SYS_Generic_CompleteFreqDriver(double max_set_freq_ppm, double max_set_freq_delay,
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lcl_ReadFrequencyDriver sys_read_freq,
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lcl_SetFrequencyDriver sys_set_freq,
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lcl_ApplyStepOffsetDriver sys_apply_step_offset,
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lcl_SetLeapDriver sys_set_leap);
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extern void SYS_Generic_Finalise(void);
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#endif /* GOT_SYS_GENERIC_H */
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