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* between the two where the value is no longer valid.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