[linux-audio-dev] Re: problem latencytest: modprobe rtc: no such device

[Takashi Iwai]

At Wed, 5 Jan 2005 13:46:11 +0100,
Maarten de Boer wrote:
> 
> Hi Takashi,
> 
> Thanks for your reply.
> 
> > Did you enable HPET? 
> 
> Hmm, it seems so... I configured my kernel using the debian .config
> as oldconfig.
> 
> $ grep HPET /boot/config-2.6.10-ck2-pentium4
> CONFIG_HPET_TIMER=y
> CONFIG_HPET=y
> # CONFIG_HPET_RTC_IRQ is not set
> CONFIG_HPET_MMAP=y
> 
> > When hpet timer is enabled, it disables RTC interrupts.
> 
> Ah, even when CONFIG_HPET_RTC_IRQ is not set??

Perhaps that's why loading rtc module _failed_.
HPET already occupies the RTC interrupt (irq 8).

When CONFIG_HPET_RTC_IRQ is set, loading rtc.ko wouldn't fail, at
least, for other RTC functions.  But latencytest wouldn't work since
RTC interrupt handling is disabled.

> > Even worse, it disables RTC irq even if HPET is not
> > detected from BIOS but only compiled.
> 
> I see... Ok, I will recompile my kernel with HPET disabled.
> But maybe a HPET version of the latencytest would be nice,
> especially since:

Yep, that wouldn't be too hard, I think.

But the problem still exists since HPET isn't enabled on many (most)
machines.  Both HPET and RTC should be supported.


Takashi