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Commit dfdf748a authored by Dominik Brodowski's avatar Dominik Brodowski Committed by Ingo Molnar
Browse files

clocksource, acpi_pm.c: use proper read function also in errata mode 



On all hardware (some Intel ICH4, PIIX4 and PIIX4E chipsets) affected by a
hardware errata there's about a 4.2% chance that initialization of the
ACPI PMTMR fails.  On those chipsets, we need to read out the timer value
at least three times to get a correct result, for every once in a while
(i.e.  within a 3 ns window every 69.8 ns) the read returns a bogus
result.  During normal operation we work around this issue, but during
initialization reading a bogus value may lead to -EINVAL even though the
hardware is usable.

Thanks to Andreas Mohr for spotting this issue.

Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 4ff4b9e1

drivers/clocksource/acpi_pm.c

+8 −8
Original line number Diff line number Diff line
@@ -151,13 +151,13 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE, 
 */

static int verify_pmtmr_rate(void)

{

	u32 value1, value2;

	cycle_t value1, value2;

	unsigned long count, delta;



	mach_prepare_counter();

	value1 = read_pmtmr();

	value1 = clocksource_acpi_pm.read();

	mach_countup(&count);

	value2 = read_pmtmr();

	value2 = clocksource_acpi_pm.read();

	delta = (value2 - value1) & ACPI_PM_MASK;



	/* Check that the PMTMR delta is within 5% of what we expect */
@@ -177,7 +177,7 @@ static int verify_pmtmr_rate(void) 


static int __init init_acpi_pm_clocksource(void)

{

	u32 value1, value2;

	cycle_t value1, value2;

	unsigned int i;



	if (!pmtmr_ioport)
@@ -187,9 +187,9 @@ static int __init init_acpi_pm_clocksource(void) 
						clocksource_acpi_pm.shift);



	/* "verify" this timing source: */

	value1 = read_pmtmr();

	value1 = clocksource_acpi_pm.read();

	for (i = 0; i < 10000; i++) {

		value2 = read_pmtmr();

		value2 = clocksource_acpi_pm.read();

		if (value2 == value1)

			continue;

		if (value2 > value1)
@@ -197,11 +197,11 @@ static int __init init_acpi_pm_clocksource(void) 
		if ((value2 < value1) && ((value2) < 0xFFF))

			goto pm_good;

		printk(KERN_INFO "PM-Timer had inconsistent results:"

			" 0x%#x, 0x%#x - aborting.\n", value1, value2);

			" 0x%#llx, 0x%#llx - aborting.\n", value1, value2);

		return -EINVAL;

	}

	printk(KERN_INFO "PM-Timer had no reasonable result:"

			" 0x%#x - aborting.\n", value1);

			" 0x%#llx - aborting.\n", value1);

	return -ENODEV;



pm_good: