53 lines
1.7 KiB
C
53 lines
1.7 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _H8300_SWITCH_TO_H
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#define _H8300_SWITCH_TO_H
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/*
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* switch_to(n) should switch tasks to task ptr, first checking that
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* ptr isn't the current task, in which case it does nothing. This
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* also clears the TS-flag if the task we switched to has used the
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* math co-processor latest.
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*/
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/*
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* switch_to() saves the extra registers, that are not saved
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* automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
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* a0-a1. Some of these are used by schedule() and its predecessors
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* and so we might get see unexpected behaviors when a task returns
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* with unexpected register values.
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*
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* syscall stores these registers itself and none of them are used
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* by syscall after the function in the syscall has been called.
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*
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* Beware that resume now expects *next to be in d1 and the offset of
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* tss to be in a1. This saves a few instructions as we no longer have
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* to push them onto the stack and read them back right after.
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*
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* 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
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*
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* Changed 96/09/19 by Andreas Schwab
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* pass prev in a0, next in a1, offset of tss in d1, and whether
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* the mm structures are shared in d2 (to avoid atc flushing).
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*
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* H8/300 Porting 2002/09/04 Yoshinori Sato
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*/
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asmlinkage void resume(void);
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#define switch_to(prev, next, last) \
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do { \
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void *_last; \
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__asm__ __volatile__( \
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"mov.l %1, er0\n\t" \
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"mov.l %2, er1\n\t" \
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"mov.l %3, er2\n\t" \
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"jsr @_resume\n\t" \
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"mov.l er2,%0\n\t" \
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: "=r" (_last) \
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: "r" (&(prev->thread)), \
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"r" (&(next->thread)), \
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"g" (prev) \
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: "cc", "er0", "er1", "er2", "er3"); \
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(last) = _last; \
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} while (0)
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#endif /* _H8300_SWITCH_TO_H */
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