From f1926ce63b996b42772b39e4b47bb4ef4ba748b4 Mon Sep 17 00:00:00 2001
From: Dominik Brodowski <linux@dominikbrodowski.net>
Date: Thu, 11 Sep 2008 11:09:49 +0200
Subject: [PATCH] clocksource, acpi_pm.c: fix check for monotonicity
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Actually check the monotonicity of the ACPI PMTMR ten times, only delay for
0.9 miliseconds at most, and bail out early if some problem is determined.
Reported-by: Jochen Voà <jochen.voss@googlemail.com>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
drivers/clocksource/acpi_pm.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 4eee533f3f4..71d2ac4e3f4 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -178,11 +178,13 @@ static int verify_pmtmr_rate(void)
/* Number of monotonicity checks to perform during initialization */
#define ACPI_PM_MONOTONICITY_CHECKS 10
+/* Number of reads we try to get two different values */
+#define ACPI_PM_READ_CHECKS 10000
static int __init init_acpi_pm_clocksource(void)
{
cycle_t value1, value2;
- unsigned int i, j, good = 0;
+ unsigned int i, j = 0;
if (!pmtmr_ioport)
return -ENODEV;
@@ -192,29 +194,26 @@ static int __init init_acpi_pm_clocksource(void)
/* "verify" this timing source: */
for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
+ udelay(100 * j);
value1 = clocksource_acpi_pm.read();
- for (i = 0; i < 10000; i++) {
+ for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
value2 = clocksource_acpi_pm.read();
if (value2 == value1)
continue;
if (value2 > value1)
- good++;
break;
if ((value2 < value1) && ((value2) < 0xFFF))
- good++;
break;
printk(KERN_INFO "PM-Timer had inconsistent results:"
" 0x%#llx, 0x%#llx - aborting.\n",
value1, value2);
return -EINVAL;
}
- udelay(300 * i);
- }
-
- if (good != ACPI_PM_MONOTONICITY_CHECKS) {
- printk(KERN_INFO "PM-Timer failed consistency check "
- " (0x%#llx) - aborting.\n", value1);
- return -ENODEV;
+ if (i == ACPI_PM_READ_CHECKS) {
+ printk(KERN_INFO "PM-Timer failed consistency check "
+ " (0x%#llx) - aborting.\n", value1);
+ return -ENODEV;
+ }
}
if (verify_pmtmr_rate() != 0)
--
2.41.3