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/*********************************************************
* Copyright (C) 2010 VMware, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation version 2.1 and no later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the Lesser GNU General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
*********************************************************/
/**
* @file pllLinux.c
*
* Implementation of the NTP PLL using Linux's adjtimex system call.
*/
#include "timeSync.h"
#include "timeSyncPosix.h"
#include <errno.h>
#include <glib.h>
#include <string.h>
#include <time.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/timex.h>
#include "vm_assert.h"
static void
TimeSyncLogPLLState(const char *prefix, struct timex *tx)
{
g_debug("%s : off %ld freq %ld maxerr %ld esterr %ld status %d "
"const %ld precision %ld tolerance %ld tick %ld\n",
prefix, tx->offset, tx->freq, tx->maxerror, tx->esterror,
tx->status, tx->constant, tx->precision, tx->tolerance, tx->tick);
}
/*
******************************************************************************
* TimeSync_PLLSupported -- */ /**
*
* Report whether the platform supports an NTP style Type-II Phase Locked
* Loop for correcting the time.
*
* @return TRUE iff NTP Phase Locked Loop is supported.
*
******************************************************************************
*/
Bool
TimeSync_PLLSupported(void)
{
return TRUE;
}
/*
******************************************************************************
* TimeSync_PLLSetFrequency -- */ /**
*
* Set the frequency of the PLL.
*
* @param[in] ppmCorrection The parts per million error that should be
* corrected. This value is the ppm shifted
* left by 16 to match NTP.
*
* @return TRUE on success.
*
******************************************************************************
*/
Bool
TimeSync_PLLSetFrequency(int64 ppmCorrection)
{
struct timex tx;
int error;
tx.modes = ADJ_FREQUENCY;
tx.freq = ppmCorrection;
error = adjtimex(&tx);
if (error == -1) {
g_debug("%s: adjtimex failed: %d %s\n", __FUNCTION__,
error, strerror(errno));
return FALSE;
}
TimeSyncLogPLLState(__FUNCTION__, &tx);
return TRUE;
}
/*
******************************************************************************
* TimeSync_PLLUpdate -- */ /**
*
* Updates the PLL with a new offset.
*
* @param[in] offset The offset between the host and the guest.
*
* @return TRUE on success.
*
******************************************************************************
*/
Bool
TimeSync_PLLUpdate(int64 offset)
{
struct timex tx;
int error;
if (offset < -500000) {
offset = -500000;
g_debug("%s: clamped offset at -500000\n", __FUNCTION__);
}
if (offset > 500000) {
offset = 500000;
g_debug("%s: clamped offset at 500000\n", __FUNCTION__);
}
tx.modes = ADJ_OFFSET | ADJ_MAXERROR | ADJ_ESTERROR;
tx.offset = offset;
tx.esterror = 0;
tx.maxerror = 0;
error = adjtimex(&tx);
if (error == -1) {
g_debug("%s: adjtimex set offset failed: %d %s\n", __FUNCTION__,
error, strerror(errno));
return FALSE;
}
TimeSyncLogPLLState(__FUNCTION__, &tx);
/* Ensure that the kernel discipline is in the right mode. STA_PLLs
* should be set and STA_UNSYNC should not be set.
*
* The time constant is a bit trickier. In "Computer Network Time
* Synchronization" the terms used are "time constant" and "poll
* exponent" where time constant = 2 ^ poll exponent. Valid values for
* the poll exponent are 4 through 17, corresponding to a range of 16s
* to 131072s (36 hours). On linux things are a bit different though:
* tx.constant appears to be the poll exponent and when trying to set
* the poll exponent, tx.constant should be set to poll exponent - 4.
*
* We want to set the time constant to as low a value as possible. The
* core NTP PLL that the kernel discipline implements is built assuming
* that there is a clock filter with a variable delay of up to 8.
* Since TimeSyncReadHostAndGuest retries if the error is large, we
* don't need to implement the clock filter. Hence we want a time
* constant of 60/8 = 7, but settle for the lowest available: 16. This
* allows us to react to changes relatively fast.
*/
if (tx.constant != 4) {
tx.modes = ADJ_TIMECONST;
tx.constant = 0;
error = adjtimex(&tx);
if (error == -1) {
g_debug("%s: adjtimex set time constant failed: %d %s\n", __FUNCTION__,
error, strerror(errno));
return FALSE;
}
g_debug("Set PLL time constant\n");
TimeSyncLogPLLState(__FUNCTION__, &tx);
}
if ((tx.status & STA_PLL) != STA_PLL || (tx.status & STA_UNSYNC) != 0) {
tx.modes = ADJ_STATUS;
tx.status = STA_PLL;
error = adjtimex(&tx);
if (error == -1) {
g_debug("%s: adjtimex set status failed: %d %s\n", __FUNCTION__,
error, strerror(errno));
return FALSE;
}
g_debug("Set PLL status\n");
TimeSyncLogPLLState(__FUNCTION__, &tx);
}
return TRUE;
}
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