Cyrix MediaGX/GXm or NSC Geode have PIT bug not TSC bug.
but in linux kernel, if CPU is Cyrix, then TSC flag is disabled.
This is not correct way, I think.
A patch atached below is originally from NetBSD kernel code.
In FreeBSD bug tracking system, this was discussed.
http://www.freebsd.org/cgi/query-pr.cgi?pr=6630
Here is NetBSD patch.
http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=8654
in this patch, this code is activate only if you defines CONFIG_CS5520.
I've tryed several month with this patch, It seems good for me.
trial machine: Casio CASSIOPEIA FIVA 101 and Fiva 103.
MediaGX 200MHz and NSC Geode 300MHz.
diff -ur kernel-source-2.4.7/arch/i386/kernel/setup.c linux/arch/i386/kernel/setup.c
--- kernel-source-2.4.7/arch/i386/kernel/setup.c Thu Jul 12 01:31:44 2001
+++ linux/arch/i386/kernel/setup.c Fri Aug 10 21:12:06 2001
@@ -1425,14 +1425,18 @@
/* GXm supports extended cpuid levels 'ala' AMD */
if (c->cpuid_level == 2) {
get_model_name(c); /* get CPU marketing name */
+#ifndef CONFIG_CS5520
clear_bit(X86_FEATURE_TSC, c->x86_capability);
+#endif
return;
}
else { /* MediaGX */
Cx86_cb[2] = (dir0_lsn & 1) ? '3' : '4';
p = Cx86_cb+2;
c->x86_model = (dir1 & 0x20) ? 1 : 2;
+#ifndef CONFIG_CS5520
clear_bit(X86_FEATURE_TSC, &c->x86_capability);
+#endif
}
break;
diff -ur kernel-source-2.4.7/arch/i386/kernel/time.c linux/arch/i386/kernel/time.c
--- kernel-source-2.4.7/arch/i386/kernel/time.c Sat Dec 30 07:07:57 2000
+++ linux/arch/i386/kernel/time.c Fri Aug 10 21:04:26 2001
@@ -28,6 +28,9 @@
* 1998-12-24 Copyright (C) 1998 Andrea Arcangeli
* Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
* serialize accesses to xtime/lost_ticks).
+ * 2001-02-20 Hiroshi Miura <[email protected]>
+ * Work around for Cyrix/IBM/NSC MediaGX/GXm, NSC Geode southbridge
+ * PIT bug. (NSC Cx5510/5520)
*/
#include <linux/errno.h>
@@ -459,6 +462,10 @@
static void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
int count;
+#ifdef CONFIG_CS5520
+ int count1, count2, count3;
+ int n1, n2, n3;
+#endif
/*
* Here we are in the timer irq handler. We just have irqs locally
@@ -487,6 +494,7 @@
rdtscl(last_tsc_low);
+#ifndef CONFIG_CS5520
spin_lock(&i8253_lock);
outb_p(0x00, 0x43); /* latch the count ASAP */
@@ -499,6 +507,59 @@
}
do_timer_interrupt(irq, NULL, regs);
+#else
+ spin_lock(&i8253_lock);
+ outb_p(0x00, 0x43); /* latch the count ASAP */
+/* this codes comes from FreeBSD */
+ count1 = inb_p(0x40);
+ count1 |= inb(0x40) << 8;
+ count2 = inb_p(0x40);
+ count2 = inb(0x40) << 8;
+ count3 = inb_p(0x40);
+ count3 = inb(0x40) << 8;
+ spin_unlock(&i8253_lock);
+
+ if (count1 >= count2 && count2 >= count3 && count1 - count2 < 0x200)
+ count = count2;
+ else {
+
+#define _swap_val(a, b) do { \
+ int c = a;\
+ a = b; \
+ b = c; \
+} while(0)
+ /* sort values */
+ if (count1 < count2)
+ _swap_val(count1, count2);
+ if (count2 < count3)
+ _swap_val(count2, count3);
+ if (count1 < count2)
+ _swap_val(count1, count2);
+
+ /* compare the middle value */
+ if (count1 - count3 < 0x200)
+ count = count2;
+ else
+ {
+ n1 = count2 - count3;
+ n2 = count3 - count1 + LATCH;
+ n3 = count1 - count2;
+ count = count3;
+ if (n1 >= n2) {
+ if (n1 >= n3)
+ count = count1;
+ } else {
+ if (n2 >= n3)
+ count = count2;
+ }
+ }
+ }
+ count = ((LATCH-1) - count) * TICK_SIZE;
+ delay_at_last_interrupt = (count + LATCH/2) / LATCH;
+ }
+
+ do_timer_interrupt(irq, NULL, regs);
+#endif
write_unlock(&xtime_lock);
@@ -659,6 +720,9 @@
if (cpu_has_tsc) {
unsigned long tsc_quotient = calibrate_tsc();
+#ifdef CONFIG_CS5520
+ if (!tsc_quotient) tsc_quotient = calibrate_tsc();
+#endif
if (tsc_quotient) {
fast_gettimeoffset_quotient = tsc_quotient;
use_tsc = 1;
Hiroshi Miura --- [email protected] http://www.da-cha.org/
CCNA, Oracle Silver Master, Network Specialist(JITEC)
My interest: http://www.cis.com.tw/Product/WS-U50R.htm
> in this patch, this code is activate only if you defines CONFIG_CS5520.
> I've tryed several month with this patch, It seems good for me.
> trial machine: Casio CASSIOPEIA FIVA 101 and Fiva 103.
> MediaGX 200MHz and NSC Geode 300MHz.
Interesting. That would explain a lot. Unfortunately when I first reported
that problem and disabled the TSC Cyrix actually refused to believe the
problem existed.
With the below it looks fixable
(The CONFIG_CS5520 we can replace I think with a check for the PCI device)
On Wed, 6 Feb 2002, Hiroshi MIURA wrote:
> I've tryed several month with this patch, It seems good for me.
> trial machine: Casio CASSIOPEIA FIVA 101 and Fiva 103.
> MediaGX 200MHz and NSC Geode 300MHz.
Does the chip fail with the readback 8254 command as well? If not, it
would be a less intrusive change.
--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: [email protected], PGP key available +
In message "Re: [PATCH] NSC Geode Companion chip workaround"
on 02/02/06, "Maciej W. Rozycki" <[email protected]> writes:
> On Wed, 6 Feb 2002, Hiroshi MIURA wrote:
>
> > I've tryed several month with this patch, It seems good for me.
> > trial machine: Casio CASSIOPEIA FIVA 101 and Fiva 103.
> > MediaGX 200MHz and NSC Geode 300MHz.
>
> Does the chip fail with the readback 8254 command as well? If not, it
> would be a less intrusive change.
OK, I want to try 8254 readback command. I will report after weekend.
Hiroshi Miura --- [email protected] http://www.da-cha.org/
CCNA, Oracle Silver Master, Network Specialist(JITEC)
My interest: http://www.cis.com.tw/Product/WS-U50R.htm
the MediaGX/Geode companion chip CS5520 fails the latch with the read-back
8254 command as well as 8253 latch command.
test program: <list1>
kernel configuration: CONFIG_M586
kernel code with read-back command: <list2>
test results:
1. kernel 2.4.16 (without any fix, TSC disable)
fails iteration: 500-1,500
value of '(now - prev)' when fail:
-100 - -200 micro sec
2. kernel 2.4.16 (with my patch)
fails iteration: 35,000-70,000
error value: -10 - -20 micro sec
3. kernel 2.4.16 (with read-back command, TSC enable)
fails iteration: 5,000-7,000
error value: about -20,000 micro sec
4. kernel 2.4.16 (without any fix but TSC enable)
fails iteration: 5,000-7,000
error value: about -20,000 micro sec
these means 'read-back command' fails as well as 'latch command'.
and my patch is better than others.
In message "Re: [PATCH] NSC Geode Companion chip workaround"
on 02/02/09, Hiroshi MIURA <[email protected]> writes:
> In message "Re: [PATCH] NSC Geode Companion chip workaround"
> on 02/02/06, "Maciej W. Rozycki" <[email protected]> writes:
> > On Wed, 6 Feb 2002, Hiroshi MIURA wrote:
> >
> > > I've tryed several month with this patch, It seems good for me.
> > > trial machine: Casio CASSIOPEIA FIVA 101 and Fiva 103.
> > > MediaGX 200MHz and NSC Geode 300MHz.
> >
> > Does the chip fail with the readback 8254 command as well? If not, it
> > would be a less intrusive change.
>
> OK, I want to try 8254 readback command. I will report after weekend.
<list1>
----------------
#include <sys/time.h>
#include <time.h>
#include <assert.h>
int main(void) {
struct timeval tv[2];
struct timeval *now, *prev;
int iterations = 0;
now = &tv[0];
prev = &tv[1];
gettimeofday(prev, NULL);
for (;;) {
struct timeval *tmp;
gettimeofday(now, NULL);
if (!((now->tv_sec > prev->tv_sec) ||
(now->tv_sec == prev->tv_sec && now->tv_usec >= prev->tv_usec)))
printf ("Err: prev: %d, %d, now: %d, %d, iter: %d\n", prev->tv_sec,
prev->tv_usec, now->tv_sec, now->tv_usec, iterations);
tmp = prev;
prev = now;
now = tmp;
iterations++;
}
return iterations;
}
----------------
<list2>
----------------
--- /usr/src/linux/arch/i386/kernel/time.c.multiread Sat Feb 9 22:24:51 2002
+++ /usr/src/linux/arch/i386/kernel/time.c.readback Sat Feb 9 20:36:41 2002
@@ -474,6 +474,7 @@
#ifdef CONFIG_CS5520
int count1, count2, count3;
int n1, n2, n3;
+ int i, cont, status;
#endif
/*
@@ -517,6 +518,26 @@
do_timer_interrupt(irq, NULL, regs);
#else
+#if 1
+ for (i = 0, cont = 1; cont && ( i < 3 ); i++) {
+ spin_lock(&i8253_lock);
+ outb_p(0xf2, 0x43); /* read-back command */
+ status = inb_p(0x40);
+ count = inb_p(0x40);
+ count |= inb_p(0x40) << 8;
+ spin_unlock(&i8253_lock);
+
+ cont = status & (1 << 6);
+ }
+
+ if (cont)
+ printk("PIT latch fails 3 times.\n");
+
+ count = ((LATCH-1) - count) * TICK_SIZE;
+ delay_at_last_interrupt = (count + LATCH/2) / LATCH;
+ }
+ do_timer_interrupt(irq, NULL, regs);
+#else
spin_lock(&i8253_lock);
outb_p(0x00, 0x43); /* latch the count ASAP */
/* this codes comes from FreeBSD */
@@ -568,6 +589,7 @@
}
do_timer_interrupt(irq, NULL, regs);
+#endif
#endif
write_unlock(&xtime_lock);
--
Hiroshi Miura --- [email protected] http://www.da-cha.org/
CCNA, Oracle Silver Master, Network Specialist(JITEC)
My interest: http://www.cis.com.tw/Product/WS-U50R.htm