Re: /dev/rtc on alpha

From: Bob McElrath (bob+linux-kernel_at_mcelrath.org)
Date: 11/09/03

  • Next message: Robert Love: "Re: preemption when running in the kernel" 
    Date:	Sun, 9 Nov 2003 09:44:36 -0800
To: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

    Ivan Kokshaysky [ink@jurassic.park.msu.ru] wrote:
    > On Sat, Nov 08, 2003 at 01:33:57PM -0800, Bob McElrath wrote:
    > > Why is the alpha kernel code grabbing the rtc interrupt? Is it possible
    > > it share its use with a user program? Would reprogramming the interrupt
    > > rate by a user program do violence to some internel kernel timing?
    >
    > On most Alphas RTC is the system timer (running at 1024 Hz).
    > So changing the interrupt rate from user space wouldn't be a good idea.

    Then I propose CONFIG_RTC be set to "n" in the arch/alpha files, and the
    /dev/rtc driver be disabled on alpha. There seems to be confusion on
    this point in the config files. CONFIG_RTC is for the /dev/rtc driver.

    Since the timer can only be set to powers of 2, it should be possible to
    simulate getting the interrupt by calling the rtc.c interrupt handler
    every 2^n interrupts...that way the user could program the timer for any
    interval less than 1024 Hz.

    Cheers,
    Bob McElrath [Univ. of California at Davis, Department of Physics]

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