lkml.org 
[lkml]   [2006]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: PMTMR running too fast
From
Date
On Mon, 2006-12-04 at 19:40 +0000, Ian Campbell wrote:
> On Mon, 2006-12-04 at 11:19 -0800, john stultz wrote:
> > On Sun, 2006-12-03 at 13:50 +0000, Ian Campbell wrote:
> > > In older kernels arch/i386/kernel/timers/timer_pm.c:verify_pmtmr_rate
> > > contained a check for sensible PMTMR rate and disabled that clocksource
> > > if it was found to be out of spec[0]. This check seems to have been lost
> > > in the transition to drivers/clocksource/acpi_pm.c, the removal is in
> > > 61743fe445213b87fb55a389c8d073785323ca3e "Time: i386 Conversion - part
> > > 4: Remove Old timer_opts Code"[1] and the check is not present in the
> > > replacement 5d0cf410e94b1f1ff852c3f210d22cc6c5a27ffa "Time: i386
> > > Clocksource Drivers"[2].
> >
> > Fedora has a bug covering this:
> > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902
>
> > > Is there a specific reason the check was removed (I couldn't see on in
> > > the archives) or was it simply overlooked? Without it I need to pass
> > > clocksource=tsc to have 2.6.18 work correctly on an older K6 system with
> > > an Aladdin chipset (will dig out the precise details if required). Would
> > > a patch to reintroduce the check be acceptable or would some sort of
> > > blacklist based solution be more acceptable?
> >
> > If I recall correctly, it was pulled because there was some question as
> > to if it was actually needed (x86_64 didn't need it) and it slows down
> > the boot time (although not by much).
> >
> > I'm fine just re-adding it. Although if the number of affected systems
> > are small we could just blacklist it (Ian, mind sending dmidecode
> > output?).

I don't have a dev box to test on at the moment, but here's a quick hack
attempt at re-adding the code. Does the following work for you?

thanks
-john


diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 7fcb77a..3379b5f 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -21,9 +21,12 @@ #include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <asm/io.h>
+#include "mach_timer.h"

/* Number of PMTMR ticks expected during calibration run */
#define PMTMR_TICKS_PER_SEC 3579545
+#define PMTMR_EXPECTED_RATE \
+ ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))

/*
* The I/O port the PMTMR resides at.
@@ -142,6 +145,36 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SE
acpi_pm_check_graylist);
#endif

+#ifndef CONFIG_X86_64
+/*
+ * Some boards have the PMTMR running way too fast. We check
+ * the PMTMR rate against PIT channel 2 to catch these cases.
+ */
+static int verify_pmtmr_rate(void)
+{
+ u32 value1, value2;
+ unsigned long count, delta;
+
+ mach_prepare_counter();
+ value1 = read_pmtmr();
+ mach_countup(&count);
+ value2 = read_pmtmr();
+ delta = (value2 - value1) & ACPI_PM_MASK;
+
+ /* Check that the PMTMR delta is within 5% of what we expect */
+ if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
+ delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
+ printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% "
+ "of normal - aborting.\n",
+ 100UL * delta / PMTMR_EXPECTED_RATE);
+ return -1;
+ }
+
+ return 0;
+}
+#else
+#define verify_pmtmr_rate() (0)
+#endif

static int __init init_acpi_pm_clocksource(void)
{
@@ -173,6 +206,9 @@ static int __init init_acpi_pm_clocksour
return -ENODEV;

pm_good:
+ if (verify_pmtmr_rate() != 0)
+ return -ENODEV;
+
return clocksource_register(&clocksource_acpi_pm);
}


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-12-04 21:17    [W:0.059 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site