Andrew,
This should go for a round or two in -mm but should be good for
inclusion into 2.6.20.
This patch re-adds the verify_pmtmr_rate functionality from 2.6.17 that
I dropped 2.6.18.
This resolves problems seen on older K6 ASUS boards where the ACPI PM
timer runs too fast.
See:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902
http://bugme.osdl.org/show_bug.cgi?id=2375
Thanks to Ian Campbell for re-reporting this and testing the fix!
Signed-off-by: John Stultz <[email protected]>
---
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 7fcb77a..8ab61ef 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -142,6 +142,39 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SE
acpi_pm_check_graylist);
#endif
+#ifndef CONFIG_X86_64
+#include "mach_timer.h"
+#define PMTMR_EXPECTED_RATE \
+ ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
+/*
+ * 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);
}