/* * programmable interrupt timer */ #include	"u.h"#include	"../port/lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"io.h"#include	"ureg.h" enum {	/* piscr */	PTE =	1<<0,	PITF =	1<<1,	PIE =	1<<2,	PS =	1<<7,}; static voidpitinterrupt(Ureg*, void*){	IMM *io; 	io = m->iomem;	if(io->piscr & PS){		io->piscr |= PS;	/* clear by writing 1 */		/* do whatever is required */	}} static voidpitreset(void){	IMM *io; 	io = ioplock();	io->piscrk = KEEP_ALIVE_KEY;	io->piscr = (PITlevel<<8) | PS | PITF;	if(0)		io->piscrk = ~KEEP_ALIVE_KEY;	/* piscrk is left unlocked for interrupt routine */	iopunlock();	intrenable(PITlevel, pitinterrupt, nil, BUSUNKNOWN, "pit");} static ulongpitload(ulong usec){	IMM *io;	ulong v; 	v = ((usec*m->oscclk)/512);	if(v == 0 || v >= (1<<16))		return 0;	/* can't do */	io = ioplock();	io->pitck = KEEP_ALIVE_KEY;	io->pitc = (v-1)<<16;	io->pitck = ~KEEP_ALIVE_KEY;	io->piscrk = KEEP_ALIVE_KEY;	io->piscr = (PITlevel<<8) | PS | PIE | PITF | PTE;	if(0)		io->piscrk = ~KEEP_ALIVE_KEY;	/* piscrk is left unlocked for interrupt routine */	iopunlock();	return (v*512)/m->oscclk;}