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/*
* Kernel interface to machine-dependent clock driver.
* Garrett Wollman, September 1994.
* This file is in the public domain.
*/
#ifndef _MACHINE_CLOCK_H_
#define _MACHINE_CLOCK_H_ 1
extern int pentium_mhz;
#ifdef I586_CPU
/*
* This resets the CPU cycle counter to zero, to make our
* job easier in microtime(). Some fancy ifdefs could speed
* this up for Pentium-only kernels.
* We want this to be done as close as possible to the actual
* timer incrementing in hardclock(), because there is a window
* between the two where the value is no longer valid. Experimentation
* may reveal a good precompensation to apply in microtime().
*/
#define CPU_CLOCKUPDATE(otime, ntime) \
do { \
if(pentium_mhz) { \
__asm __volatile("cli\n" \
"movl (%2),%%eax\n" \
"movl %%eax,(%1)\n" \
"movl 4(%2),%%eax\n" \
"movl %%eax,4(%1)\n" \
"movl $0x10,%%ecx\n" \
"xorl %%eax,%%eax\n" \
"movl %%eax,%%edx\n" \
".byte 0x0f, 0x30\n" \
"sti\n" \
"#%0%1%2" \
: "=m"(*otime) /* no outputs */ \
: "c"(otime), "b"(ntime) /* fake input */ \
: "ax", "cx", "dx"); \
} else { \
*(otime) = *(ntime); \
} \
} while(0)
#else
#define CPU_CLOCKUPDATE(otime, ntime) \
(*(otime) = *(ntime))
#endif
#endif /* _MACHINE_CLOCK_H_ */
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