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

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

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