40 lines
866 B
C
40 lines
866 B
C
/* vim: tabstop=4 shiftwidth=4 noexpandtab
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*
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* Tiny FPU enable module.
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*
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* Part of the ToAruOS Kernel
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* (C) 2011 Kevin Lange ...
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* To whatever possible level this short of a code chunk
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* can be considered copyrightable in your jurisdiction.
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*/
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#include <system.h>
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#include <logging.h>
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/**
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* Set the FPU control word
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*
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* @param cw What to set the control word to.
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*/
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void
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set_fpu_cw(const uint16_t cw) {
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asm volatile("fldcw %0" :: "m"(cw));
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}
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/**
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* Enable the FPU
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*
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* We are assuming that we have one to begin with, but since we
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* only really operate on 686 machines, we do, so we're not
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* going to bother checking.
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*/
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void
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enable_fpu() {
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debug_print(NOTICE, "Enabling floating-point arithmetic unit");
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size_t cr4;
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asm volatile ("mov %%cr4, %0" : "=r"(cr4));
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cr4 |= 0x200;
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asm volatile ("mov %0, %%cr4" :: "r"(cr4));
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set_fpu_cw(0x37F);
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}
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