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IT8172G on-board timers

Subject: IT8172G on-board timers
From: Dmitry Antipov <>
Date: Tue, 05 Aug 2003 17:38:40 +0400
Original-recipient: rfc822;
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Hello all,

I'm working with IT8172-based MIPS board and want to use one of (or may be both) on-board timers. For my purposes, it's required to generate irq from timer rarely, for example, each 1 sec, or each 5 sec or so. (The usage of Linux timer interface (init_timer() etc...) is forbidden, and I don't want to touch system timer to avoid the potential damage for basic timekeeping, scheduling, etc.). I have two problems: - timer backward counter is 16-bit wide and reaches zero too fast, even starting from 0xffff; - timer input clock may be one of CPU clock, CPU clock /4, CPU clock/8 or CPU clock /16, which looks
  very fast too
So, the minimum interrupt frequency from both timers is 96 ints/HZ (with TCR0.PST0 is 0 and TCVR0 is 0xffff) and the maximum is around 150000 ints/HZ. Even the minimum is too large for me...

It seems this question is much more about h/w than about Linux, but I hope someone has an experience with this arch :-) Is it possible to program on-board timer to generate interrupts with less frequency ?


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