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>
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12d6d41276
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b519508298
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@ -23,6 +23,7 @@
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#include <linux/init.h>
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#include <linux/pci.h>
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#include <linux/delay.h>
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#include <linux/async.h>
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#include <asm/io.h>
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/*
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@ -179,17 +180,15 @@ static int verify_pmtmr_rate(void)
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/* Number of reads we try to get two different values */
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#define ACPI_PM_READ_CHECKS 10000
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static int __init init_acpi_pm_clocksource(void)
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static void __init acpi_pm_clocksource_async(void *unused, async_cookie_t cookie)
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{
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cycle_t value1, value2;
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unsigned int i, j = 0;
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if (!pmtmr_ioport)
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return -ENODEV;
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/* "verify" this timing source: */
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for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
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udelay(100 * j);
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usleep_range(100 * j, 100 * j + 100);
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value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
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for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
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value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
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@ -203,25 +202,34 @@ static int __init init_acpi_pm_clocksource(void)
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" 0x%#llx, 0x%#llx - aborting.\n",
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value1, value2);
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pmtmr_ioport = 0;
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return -EINVAL;
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return;
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}
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if (i == ACPI_PM_READ_CHECKS) {
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printk(KERN_INFO "PM-Timer failed consistency check "
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" (0x%#llx) - aborting.\n", value1);
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pmtmr_ioport = 0;
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return -ENODEV;
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return;
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}
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}
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if (verify_pmtmr_rate() != 0){
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pmtmr_ioport = 0;
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return -ENODEV;
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return;
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}
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return clocksource_register_hz(&clocksource_acpi_pm,
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clocksource_register_hz(&clocksource_acpi_pm,
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PMTMR_TICKS_PER_SEC);
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}
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static int __init init_acpi_pm_clocksource(void)
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{
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if (!pmtmr_ioport)
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return -ENODEV;
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async_schedule(acpi_pm_clocksource_async, NULL);
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return 0;
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}
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/* We use fs_initcall because we want the PCI fixups to have run
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* but we still need to load before device_initcall
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*/
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