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Annotation of coherent/b/STREAMS/coh.386/clocked.c, revision 1.1.1.1

1.1       root        1: /* $Header: /src386/STREAMS/coh.386/RCS/clocked.c,v 2.2 93/08/09 13:35:17 bin Exp Locker: bin $ */
                      2: /*
                      3:  * clocked.c - support routines for alternate clock rate
                      4:  *
                      5:  *  altclk_in(hz, fn) - install routine with specified rate
                      6:  *                      "hz" should be a multiple of system rate of 100 Hz
                      7:  *                     return 0 if completed ok, -1 otherwise
                      8:  *
                      9:  *  altclk_out()      - uninstall alternate clock routine and restore system rate
                     10:  *                     return old value of "altclk"
                     11:  *
                     12:  *  altclk_rate(hz)   - set clock interrupt rate
                     13:  *                     new rate must be an even multiple of system rate "HZ"
                     14:  *                     return 0 if completed ok, -1 otherwise
                     15:  *
                     16:  *  History:
                     17:  *    90/08/08 hws     initial version, works with hs.c modified for com[1-4]
                     18:  *    90/08/14 hws     make it more like a Unix system call
                     19:  *
                     20:  * $Log:       clocked.c,v $
                     21:  * Revision 2.2  93/08/09  13:35:17  bin
                     22:  * Kernel 82 changes
                     23:  * 
                     24:  * Revision 2.2  93/07/26  15:22:04  nigel
                     25:  * Nigel's R80
                     26:  * 
                     27:  */
                     28: 
                     29: #include       <sys/coherent.h>                /* altclk */
                     30: 
                     31: #ifdef _I386
                     32: #include       <kernel/param.h>                /* HZ */
                     33: #else
                     34: #include       <kernel/const.h>                /* HZ */
                     35: #endif
                     36: 
                     37: #define        PIT     0x40            /* 8253 port */
                     38: #define        TMR0_M3 0x36            /* timer 0, mode 3 */
                     39: #define        SYS_HZ  1193200L        /* rate of input clock to timer 0 */
                     40: 
                     41: typedef int (*PFI)();          /* pointer to function returning int */
                     42: 
                     43: altclk_rate(hz)
                     44: unsigned int hz;
                     45: {
                     46:        int s;                  /* to save CPU irpt flag */
                     47:        unsigned int interval;  /* period for hz, in units of 1.19 MHz ticks */
                     48:        int ret;
                     49: 
                     50:        if (hz >= HZ && hz % HZ == 0) {         /* can't go slower than HZ! */
                     51:                interval = SYS_HZ/hz;
                     52:                s = sphi();                     /* disable irpts */
                     53:                outb(PIT+3, TMR0_M3);
                     54:                outb(PIT, interval & 0xff);
                     55:                outb(PIT, interval >> 8);       /* unsigned shift */
                     56:                spl(s);                         /* restore previous irpt state */
                     57:                ret = 0;
                     58:        } else {
                     59:                ret = -1;
                     60:        }
                     61:        return ret;
                     62: }
                     63: 
                     64: int altclk_in(hz, fn)
                     65: int hz;
                     66: PFI fn;
                     67: {
                     68:        int ret;
                     69: 
                     70:        if ((ret = altclk_rate(hz)) == 0)
                     71:                altclk = fn;
                     72:        return ret;
                     73: }
                     74: 
                     75: PFI altclk_out()
                     76: {
                     77:        PFI ret;
                     78: 
                     79:        ret = altclk;
                     80:        if (ret) {
                     81:                altclk_rate(HZ);
                     82:                altclk = 0;
                     83:        }
                     84:        return ret;
                     85: }

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