clock.h revision 3307 
1/*
2 * Kernel interface to machine-dependent clock driver.
3 * Garrett Wollman, September 1994.
4 * This file is in the public domain.
5 */
6
7#ifndef _MACHINE_CLOCK_H_
8#define _MACHINE_CLOCK_H_ 1
9
10void inittodr(time_t base);
11
12extern int pentium_mhz;
13
14#ifdef I586_CPU
15	/*
16	 * This resets the CPU cycle counter to zero, to make our
17	 * job easier in microtime().  Some fancy ifdefs could speed
18	 * this up for Pentium-only kernels.
19	 * We want this to be done as close as possible to the actual
20	 * timer incrementing in hardclock(), because there is a window
21	 * between the two where the value is no longer valid.  Experimentation
22	 * may reveal a good precompensation to apply in microtime().
23	 */
24#define CPU_CLOCKUPDATE(otime, ntime) \
25	do { \
26	if(pentium_mhz) { \
27		__asm __volatile("cli\n" \
28				 "movl (%2),%%eax\n" \
29				 "movl %%eax,(%1)\n" \
30				 "movl 4(%2),%%eax\n" \
31				 "movl %%eax,4(%1)\n" \
32				 "movl $0x10,%%ecx\n" \
33				 "xorl %%eax,%%eax\n" \
34				 "movl %%eax,%%edx\n" \
35				 ".byte 0x0f, 0x30\n" \
36				 "sti\n" \
37				 "#%0%1%2" \
38				 : "=m"(*otime)	/* no outputs */ \
39				 : "c"(otime), "b"(ntime) /* fake input */ \
40				 : "ax", "cx", "dx"); \
41	} else { \
42		*(otime) = *(ntime); \
43	} \
44	} while(0)
45
46#else
47#define CPU_CLOCKUPDATE(otime, ntime) \
48		(*(otime) = *(ntime))
49#endif
50
51#endif /* _MACHINE_CLOCK_H_ */
52