diff options
| author | Arjan van de Ven <arjan@linux.intel.com> | 2012-01-30 20:23:30 -0800 |
|---|---|---|
| committer | John Stultz <john.stultz@linaro.org> | 2012-02-01 18:39:46 -0800 |
| commit | b519508298e0292e1771eecf14aaf67755adc39d (patch) | |
| tree | 31fd0675057bb14e3dcff26d585fd512614b181b /drivers/clocksource | |
| parent | 12d6d41276def096cb3f7dc36f438db9ed6a0a8d (diff) | |
| download | linux-3.10-b519508298e0292e1771eecf14aaf67755adc39d.tar.gz linux-3.10-b519508298e0292e1771eecf14aaf67755adc39d.tar.bz2 linux-3.10-b519508298e0292e1771eecf14aaf67755adc39d.zip | |
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 <johnstul@us.ibm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Len Brown <lenb@kernel.org>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/acpi_pm.c | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c index 6b5cf02c35c..82e882028fc 100644 --- a/drivers/clocksource/acpi_pm.c +++ b/drivers/clocksource/acpi_pm.c @@ -23,6 +23,7 @@ #include <linux/init.h> #include <linux/pci.h> #include <linux/delay.h> +#include <linux/async.h> #include <asm/io.h> /* @@ -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 */ |