x86/ioapic: Refactor the delay logic in timer_irq_works()
timer_irq_works() is used to detects the timer IRQs. It calls mdelay(10) to delay ten ticks and check whether the timer IRQ work or not. mdelay() depends on the loops_per_jiffy which is set up in calibrate_delay(), but the delay calibration depends on a working timer interrupt, which causes a chicken and egg problem. The correct solution is to set up the interrupt mode and making sure that the timer interrupt is delivered correctly before invoking calibrate_delay(). That means that mdelay() cannot be used in timer_irq_works(). Provide helper functions to make a rough delay estimate which is good enough to prove that the timer interrupt is working. Either use TSC or a simple delay loop and assume that 4GHz is the maximum CPU frequency to base the delay calculation on. Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: yinghai@kernel.org Cc: bhe@redhat.com Link: https://lkml.kernel.org/r/1505293975-26005-9-git-send-email-douly.fnst@cn.fujitsu.com
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