Re: [Linux-ia64] RTC support on ia64

From: Joel GUILLET <>
Date: 2002-12-19 02:01:56
On Wed, 18 Dec 2002, Peter Chubb wrote:

> >>>>> "Alex" == Alex Williamson <> writes:
> Alex> Joel, Does this provide more functionality than the EFI RTC?
> Alex> Concerns I have w/ it on ia64 is that the rtc driver assumes you
> Alex> have a legacy rtc at the legacy irq and port address.  This
> Alex> won't work on HP zx1 boxes, the legacy hardware doesn't exist.
> Alex> In the future, there's a possibility that the port address could
> Alex> be allocated to non-legacy purposes.  Maybe ACPI could tell you
> Alex> if you have a legacy RTC, it could at least tell you if you
> Alex> support PC/AT compatible interrupts.  Thanks,
Peter> Yes it does.  There's no way to get a regular interrupt into user
Peter> space from the EFI RTC.

The RTC legacy hardware seems to be on the i870 chipset. And if you don't
have this one, you may not be able to use it.

Peter> I've been using the PMU to generate regular interrupts, and have a
Peter> locally-modified amlat benchmark that does that.

Did you modify anything inside the kernel to make use of this timer ?
With PMU, you mean "Performance Monitoring Unit" or "Power Management
Utility" ? -- this question may look strange but with the acutal high
resolution timer his ACPI PowerManagement timer, I've finally got some

I had a looked at the PMU code but I couldn't find anything about the way
of using this timer ? Is it built-in somewhere ?
Do I need to implement some code in the kernel to use it ? I've
been trying to find some docs in the Web for quite a long time ... but
without any results ! Does an user interface already exist ?

Thanks for your help.


** Joel
Received on Wed Dec 18 07:01:46 2002

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