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Annotation of coherent/d/286_KERNEL/USRSRC/286/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: #include       <sys/const.h>           /* HZ */
                     22: 
                     23: #define        PIT     0x40            /* 8253 port */
                     24: #define        TMR0_M3 0x36            /* timer 0, mode 3 */
                     25: 
                     26: #if 0
                     27:                                /* nominal IBM rate is 1.1900 MHz */
                     28: #define        SYS_HZ  1190000L        /* rate of input clock to timer 0 */
                     29: #else
                     30:                                /* current kernel rate is 1.1932 MHz */
                     31: #define        SYS_HZ  1193200L        /* rate of input clock to timer 0 */
                     32: #endif
                     33: 
                     34: typedef int (*PFI)();          /* pointer to function returning int */
                     35: 
                     36: altclk_rate(hz)
                     37: unsigned int hz;
                     38: {
                     39:        int s;                  /* to save CPU irpt flag */
                     40:        unsigned int interval;  /* period for hz, in units of 1.19 MHz ticks */
                     41:        int ret;
                     42: 
                     43:        if (hz >= HZ && hz % HZ == 0) {         /* can't go slower than HZ! */
                     44:                interval = SYS_HZ/hz;
                     45:                s = sphi();                     /* disable irpts */
                     46:                outb(PIT+3, TMR0_M3);
                     47:                outb(PIT, interval & 0xff);
                     48:                outb(PIT, interval >> 8);       /* unsigned shift */
                     49:                spl(s);                         /* restore previous irpt state */
                     50:                ret = 0;
                     51:        } else {
                     52:                ret = -1;
                     53:        }
                     54:        return ret;
                     55: }
                     56: 
                     57: int altclk_in(hz, fn)
                     58: int hz;
                     59: PFI fn;
                     60: {
                     61:        int ret;
                     62: 
                     63:        if ((ret = altclk_rate(hz)) == 0)
                     64:                altclk = fn;
                     65:        return ret;
                     66: }
                     67: 
                     68: PFI altclk_out()
                     69: {
                     70:        PFI ret;
                     71: 
                     72:        ret = altclk;
                     73:        if (ret) {
                     74:                altclk_rate(HZ);
                     75:                altclk = 0;
                     76:        }
                     77:        return ret;
                     78: }

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