(2013/09/03 21:44), Eric W. Biederman wrote: > Yoshihiro YUNOMAE <yoshihiro.yunomae...@hitachi.com> writes: > >> (2013/09/03 9:12), Eric W. Biederman wrote: >>>>>> Then again looking at the output of the latest dmesg, it seems the IO >>>>>> APIC >>>>>> is initialized way before the tsc is calibrated. So I am not sure what >>>>>> needed to get done or what interrupts are needed before the IO APIC gets >>>>>> initialized. >>>>> >>>>> The practical issue is that jiffies was calibrated off of the PIT timer >>>>> if I recall. But that is all old news. >>>> >>>> Are the jiffies calibration codes calibrate_delay()? >>>> It seems that the jiffies calibration have not used PIT in 2005 >>>> according to 8a9e1b0. >>> >>> Exactly. That was the original reason why we put in the code to >>> disable the IOAPIC and the local apic. There might have been other >>> reasons but that was the primary. >> >> Thanks, but I have still a question for jiffies calibration. >> >> When kernel boots, calibrate_delay_direct() will be called in >> calibrate_delay() for calculating loops_per_jiffy. Then, >> calibrate_delay_direct() waits until jiffies is incremented. >> I think this means PIT or HPET is still used for the calibration. >> Is there something wrong with my understanding? >> If wrong, how is jiffies incremented? > > Things have definitely changed, and I believe part of what you are > seeing is the path when things are not calibrated by an arch specific > means. > > Ulimately the issue was not that we waited (or possibly still wait) for > a timer interrupt to calibrate the delay loop. The problem was that we > had initialized the interrupt controller in PIC mode (when the kernel > did not later use the interrupt controller in PIC mode) to receive the > interrupt. > > The actual impetus for getting the last of the bugs shaken out is that > we have subarchitectures on x86 that do no support interrupt controllers > in PIC mode at all.
Is one of the subarchitectures Moorestown? I found the Moorestown patch(05ddafb) which defined pre_init_apic_IRQ0(). If this function will enable IOAPIC before using timer(i.e. the function is called before calibrate_delay()), we will be able to remove disable_IO_APIC. However, this function is a Moorestown specific code, and normal PCs don't execute it. I haven't find the generic cord which operates like pre_init_apic_IRQ0() yet. Please tell me if you remember something. Thanks, Yoshihiro YUNOMAE -- Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: yoshihiro.yunomae...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
