1 /* 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This software was developed by the Computer Systems Engineering group 6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 7 * contributed to Berkeley. 8 * 9 * All advertising materials mentioning features or use of this software 10 * must display the following acknowledgement: 11 * This product includes software developed by the University of 12 * California, Lawrence Berkeley Laboratory. 13 * 14 * %sccs.include.redist.c% 15 * 16 * @(#)timerreg.h 8.1 (Berkeley) 06/11/93 17 * 18 * from: $Header: timerreg.h,v 1.7 92/11/26 03:05:09 leres Exp $ (LBL) 19 */ 20 21 /* 22 * Sun-4c counter/timer registers. The timers are implemented within 23 * the cache chip (!). The counter and limit fields below could be 24 * defined as: 25 * 26 * struct { 27 * u_int t_limit:1, // limit reached 28 * t_usec:21, // counter value in microseconds 29 * t_mbz:10; // always zero 30 * }; 31 * 32 * but this is more trouble than it is worth. 33 * 34 * These timers work in a rather peculiar fashion. Most clock counters 35 * run to 0 (as, e.g., on the VAX, where the ICR counts up to 0 from a 36 * large unsigned number). On the Sun-4c, it counts up to a limit. But 37 * for some reason, when it reaches the limit, it resets to 1, not 0. 38 * Thus, if the limit is set to 4, the counter counts like this: 39 * 40 * 1, 2, 3, 1, 2, 3, ... 41 * 42 * and if we want to divide by N we must set the limit register to N+1. 43 */ 44 #ifndef LOCORE 45 struct timer { 46 int t_counter; /* counter reg */ 47 int t_limit; /* limit reg */ 48 }; 49 50 struct timerreg { 51 struct timer t_c10; /* counter that interrupts at ipl 10 */ 52 struct timer t_c14; /* counter that interrupts at ipl 14 */ 53 }; 54 #endif 55 56 #define TMR_LIMIT 0x80000000 /* counter reached its limit */ 57 #define TMR_SHIFT 10 /* shift to obtain microseconds */ 58 #define TMR_MASK 0x1fffff /* 21 bits */ 59 60 /* Compute a limit that causes the timer to fire every n microseconds. */ 61 #define tmr_ustolim(n) (((n) + 1) << TMR_SHIFT) 62 63 #include <sparc/sparc/vaddrs.h> 64 #define TIMERREG ((volatile struct timerreg *)TIMERREG_VA) 65