Hi Andreas,
On Sun, Aug 10, 2008 at 09:08:02PM +0200, Andreas Mohr wrote:
> And it's in fact not this triple-read which has any weakness here but rather
> the init check.
right.
> IMHO the current init check is too weak, it will catch the very simplest
> types of problems only, and that's not a good thing.
what about this?
Best,
Dominik
acpi_pm.c: check for monotonicity
Expand the check for monotonicity by doing ten tests instead of one.
Applies on top of "acpi_pm.c: use proper read function also in errata mode."
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxx>
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 2c00edd..f05c4fb 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -178,7 +178,7 @@ static int verify_pmtmr_rate(void)
static int __init init_acpi_pm_clocksource(void)
{
cycle_t value1, value2;
- unsigned int i;
+ unsigned int i, j, good = 0;
if (!pmtmr_ioport)
return -ENODEV;
@@ -187,24 +187,32 @@ static int __init init_acpi_pm_clocksource(void)
clocksource_acpi_pm.shift);
/* "verify" this timing source: */
- value1 = clocksource_acpi_pm.read();
- for (i = 0; i < 10000; i++) {
- value2 = clocksource_acpi_pm.read();
- if (value2 == value1)
- continue;
- if (value2 > value1)
- goto pm_good;
- if ((value2 < value1) && ((value2) < 0xFFF))
- goto pm_good;
- printk(KERN_INFO "PM-Timer had inconsistent results:"
- " 0x%#llx, 0x%#llx - aborting.\n", value1, value2);
- return -EINVAL;
+ for (j = 0; j < 10; j++) {
+ value1 = clocksource_acpi_pm.read();
+ for (i = 0; i < 10000; 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 != 10) {
+ printk(KERN_INFO "PM-Timer had no reasonable result:"
+ " 0x%#llx - aborting.\n", value1);
+ return -ENODEV;
}
- printk(KERN_INFO "PM-Timer had no reasonable result:"
- " 0x%#llx - aborting.\n", value1);
- return -ENODEV;
-pm_good:
if (verify_pmtmr_rate() != 0)
return -ENODEV;
--
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