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Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt
From: Lee Revell <rlrevell@joe-job.com>
To: Jesper Juhl <jesper.juhl@gmail.com>
Cc: Linus Torvalds <torvalds@osdl.org>, Chris Wedgwood <cw@f00f.org>,
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Date: Sat, 16 Jul 2005 22:35:24 -0400
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On Sun, 2005-07-17 at 04:13 +0200, Jesper Juhl wrote:
> Where do we actually program the tick rate we want?
> 

In arch/i386/kernel/timers/timer_pit.c:

    166 void setup_pit_timer(void)
    167 {
    168         unsigned long flags;
    169 
    170         spin_lock_irqsave(&i8253_lock, flags);
    171         outb_p(0x34,PIT_MODE);          /* binary, mode 2, LSB/MSB, ch 0 */
    172         udelay(10);
    173         outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
    174         udelay(10);
    175         outb(LATCH >> 8 , PIT_CH0);     /* MSB */
    176         spin_unlock_irqrestore(&i8253_lock, flags);
    177 }
    178 

Lee