Date: Tue, 18 May 1999 10:08:15 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: John Polstra <jdp@polstra.com> Cc: alpha@freebsd.org Subject: Re: Clock drift on the alpha Message-ID: <Pine.BSF.4.05.9905181007370.509-100000@herring.nlsystems.com> In-Reply-To: <XFMail.990517184404.jdp@polstra.com>
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On Mon, 17 May 1999, John Polstra wrote:
> My alpha machine, which I suspect may be haunted, has pretty bad clock
> drift. I started up xntpd, and the log messages will give you a sense
> of how bad the drift is:
Could you try this patch and see if it keeps better time:
Index: alpha/alpha/clock.c
===================================================================
RCS file: /home/ncvs/src/sys/alpha/alpha/clock.c,v
retrieving revision 1.8
diff -u -r1.8 clock.c
--- clock.c 1999/04/25 10:45:59 1.8
+++ clock.c 1999/05/18 09:01:54
@@ -114,6 +114,7 @@
static u_int32_t last_time;
static void handleclock(void* arg);
+static u_int32_t calibrate_clocks(u_int32_t firmware_freq);
void
clockattach(device_t dev)
@@ -150,6 +151,8 @@
void
cpu_initclocks()
{
+ u_int32_t freq;
+
if (clockdev == NULL)
panic("cpu_initclocks: no clock attached");
@@ -175,11 +178,12 @@
* hardclock, which would then fall over because p->p_stats
* isn't set at that time.
*/
+ freq = calibrate_clocks(cycles_per_sec);
last_time = alpha_rpcc();
- scaled_ticks_per_cycle = ((u_int64_t)hz << FIX_SHIFT) / cycles_per_sec;
- max_cycles_per_tick = 2*cycles_per_sec / hz;
+ scaled_ticks_per_cycle = ((u_int64_t)hz << FIX_SHIFT) / freq;
+ max_cycles_per_tick = 2*freq / hz;
- alpha_timecounter.tc_frequency = cycles_per_sec;
+ alpha_timecounter.tc_frequency = freq;
init_timecounter(&alpha_timecounter);
platform.clockintr = (void (*) __P((void *))) handleclock;
@@ -188,6 +192,60 @@
* Get the clock started.
*/
CLOCK_INIT(clockdev);
+}
+
+static u_int32_t
+calibrate_clocks(u_int32_t firmware_freq)
+{
+ u_int32_t start_pcc, stop_pcc;
+ int sec, start_sec;
+
+ if (bootverbose)
+ printf("Calibrating clock(s) ... ");
+
+ /* Read the mc146818A seconds counter. */
+ if (CLOCK_GETSECS(clockdev, &sec))
+ goto fail;
+
+ /* Wait for the mC146818A seconds counter to change. */
+ start_sec = sec;
+ for (;;) {
+ if (CLOCK_GETSECS(clockdev, &sec))
+ goto fail;
+ if (sec != start_sec)
+ break;
+ }
+
+ /* Start keeping track of the PCC. */
+ start_pcc = alpha_rpcc();
+
+ /*
+ * Wait for the mc146818A seconds counter to change.
+ */
+ start_sec = sec;
+ for (;;) {
+ if (CLOCK_GETSECS(clockdev, &sec))
+ goto fail;
+ if (sec != start_sec)
+ break;
+ }
+
+ /*
+ * Read the PCC again to work out frequency.
+ */
+ stop_pcc = alpha_rpcc();
+
+ if (bootverbose) {
+ printf("PCC clock: %u Hz (firmware %u Hz)\n",
+ stop_pcc - start_pcc, firmware_freq);
+ }
+ return (stop_pcc - start_pcc);
+
+fail:
+ if (bootverbose)
+ printf("failed, using firmware default of %u Hz\n",
+ firmware_freq);
+ return (firmware_freq);
}
static void
Index: alpha/alpha/clock_if.m
===================================================================
RCS file: /home/ncvs/src/sys/alpha/alpha/clock_if.m,v
retrieving revision 1.2
diff -u -r1.2 clock_if.m
--- clock_if.m 1998/11/08 18:35:51 1.2
+++ clock_if.m 1999/05/18 09:01:18
@@ -44,3 +44,8 @@
device_t dev;
struct clocktime *ct;
};
+
+METHOD int getsecs {
+ device_t dev;
+ int *secp;
+};
Index: alpha/isa/mcclock_isa.c
===================================================================
RCS file: /home/ncvs/src/sys/alpha/isa/mcclock_isa.c,v
retrieving revision 1.4
diff -u -r1.4 mcclock_isa.c
--- mcclock_isa.c 1999/05/08 21:58:38 1.4
+++ mcclock_isa.c 1999/05/18 08:48:15
@@ -61,6 +61,7 @@
DEVMETHOD(clock_init, mcclock_init),
DEVMETHOD(clock_get, mcclock_get),
DEVMETHOD(clock_set, mcclock_set),
+ DEVMETHOD(clock_getsecs, mcclock_getsecs),
{ 0, 0 }
};
Index: alpha/tlsb/mcclock_tlsb.c
===================================================================
RCS file: /home/ncvs/src/sys/alpha/tlsb/mcclock_tlsb.c,v
retrieving revision 1.4
diff -u -r1.4 mcclock_tlsb.c
--- mcclock_tlsb.c 1999/05/08 21:58:53 1.4
+++ mcclock_tlsb.c 1999/05/18 08:48:52
@@ -74,6 +74,7 @@
DEVMETHOD(clock_init, mcclock_init),
DEVMETHOD(clock_get, mcclock_get),
DEVMETHOD(clock_set, mcclock_set),
+ DEVMETHOD(clock_getsecs, mcclock_getsecs),
{ 0, 0 }
};
Index: dev/dec/mcclock.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/dec/mcclock.c,v
retrieving revision 1.2
diff -u -r1.2 mcclock.c
--- mcclock.c 1998/06/14 13:45:41 1.2
+++ mcclock.c 1999/05/18 09:02:08
@@ -111,3 +111,29 @@
MC146818_PUTTOD(dev, ®s);
splx(s);
}
+
+int
+mcclock_getsecs(device_t dev, int *secp)
+{
+ int timeout = 100000000;
+ int sec;
+ int s;
+
+ s = splclock();
+ for (;;) {
+ if (!(MCCLOCK_READ(dev, MC_REGA) & MC_REGA_UIP)) {
+ sec = MCCLOCK_READ(dev, MC_SEC);
+ break;
+ }
+ if (--timeout == 0)
+ goto fail;
+ }
+
+ splx(s);
+ *secp = sec;
+ return 0;
+
+ fail:
+ splx(s);
+ return ETIMEDOUT;
+}
Index: dev/dec/mcclockvar.h
===================================================================
RCS file: /home/ncvs/src/sys/dev/dec/mcclockvar.h,v
retrieving revision 1.2
diff -u -r1.2 mcclockvar.h
--- mcclockvar.h 1998/06/14 13:45:42 1.2
+++ mcclockvar.h 1999/05/18 08:48:32
@@ -33,3 +33,4 @@
void mcclock_init(device_t);
void mcclock_get(device_t, time_t, struct clocktime *);
void mcclock_set(device_t, struct clocktime *);
+int mcclock_getsecs(device_t dev, int *secp);
--
Doug Rabson Mail: dfr@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 442 9037
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