From b519508298e0292e1771eecf14aaf67755adc39d Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Mon, 30 Jan 2012 20:23:30 -0800 Subject: [PATCH] clocksource: Load the ACPI PM clocksource asynchronously The ACPI clocksource takes quite some time to initialize, and this increases the boot time of the kernel for a double digit percentage. This while almost all modern systems will be using the HPET already anyway. This patch turns the clocksource loading into an asynchronous operation; which means it won't hold up the boot while still becoming available normally. To make this work well, an udelay() had to be turned into an usleep_range() so that on UP systems, we yield the CPU to regular boot tasks instead of spinning. CC: John Stultz CC: Thomas Gleixner CC: Len Brown Signed-off-by: Arjan van de Ven Signed-off-by: John Stultz --- drivers/clocksource/acpi_pm.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c index 6b5cf02c35c8..82e882028fcf 100644 --- a/drivers/clocksource/acpi_pm.c +++ b/drivers/clocksource/acpi_pm.c @@ -23,6 +23,7 @@ #include #include #include +#include #include /* @@ -179,17 +180,15 @@ static int verify_pmtmr_rate(void) /* Number of reads we try to get two different values */ #define ACPI_PM_READ_CHECKS 10000 -static int __init init_acpi_pm_clocksource(void) +static void __init acpi_pm_clocksource_async(void *unused, async_cookie_t cookie) { cycle_t value1, value2; unsigned int i, j = 0; - if (!pmtmr_ioport) - return -ENODEV; /* "verify" this timing source: */ for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) { - udelay(100 * j); + usleep_range(100 * j, 100 * j + 100); value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); for (i = 0; i < ACPI_PM_READ_CHECKS; i++) { value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); @@ -203,25 +202,34 @@ static int __init init_acpi_pm_clocksource(void) " 0x%#llx, 0x%#llx - aborting.\n", value1, value2); pmtmr_ioport = 0; - return -EINVAL; + return; } if (i == ACPI_PM_READ_CHECKS) { printk(KERN_INFO "PM-Timer failed consistency check " " (0x%#llx) - aborting.\n", value1); pmtmr_ioport = 0; - return -ENODEV; + return; } } if (verify_pmtmr_rate() != 0){ pmtmr_ioport = 0; - return -ENODEV; + return; } - return clocksource_register_hz(&clocksource_acpi_pm, + clocksource_register_hz(&clocksource_acpi_pm, PMTMR_TICKS_PER_SEC); } +static int __init init_acpi_pm_clocksource(void) +{ + if (!pmtmr_ioport) + return -ENODEV; + + async_schedule(acpi_pm_clocksource_async, NULL); + return 0; +} + /* We use fs_initcall because we want the PCI fixups to have run * but we still need to load before device_initcall */ -- 2.20.1