arch/mips/include/asm/switch_to.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994, 95, 96, 97, 98, 99, 2003, 06 by Ralf Baechle
   7  * Copyright (C) 1996 by Paul M. Antoine
   8  * Copyright (C) 1999 Silicon Graphics
   9  * Kevin D. Kissell, kevink@mips.org and Carsten Langgaard, carstenl@mips.com
  10  * Copyright (C) 2000 MIPS Technologies, Inc.
  11  */
  12 #ifndef _ASM_SWITCH_TO_H
  13 #define _ASM_SWITCH_TO_H
  14
  15 #include <asm/cpu-features.h>
  16 #include <asm/watch.h>
  17 #include <asm/dsp.h>
  18 #include <asm/cop2.h>
  19 #include <asm/msa.h>
  20
  21 struct task_struct;
  22
  23 enum {
  24         FP_SAVE_NONE    = 0,
  25         FP_SAVE_VECTOR  = -1,
  26         FP_SAVE_SCALAR  = 1,
  27 };
  28
  29 /**
  30  * resume - resume execution of a task
  31  * @prev:       The task previously executed.
  32  * @next:       The task to begin executing.
  33  * @next_ti:    task_thread_info(next).
  34  * @fp_save:    Which, if any, FP context to save for prev.
  35  *
  36  * This function is used whilst scheduling to save the context of prev & load
  37  * the context of next. Returns prev.
  38  */
  39 extern asmlinkage struct task_struct *resume(struct task_struct *prev,
  40                 struct task_struct *next, struct thread_info *next_ti,
  41                 s32 fp_save);
  42
  43 extern unsigned int ll_bit;
  44 extern struct task_struct *ll_task;
  45
  46 #ifdef CONFIG_MIPS_MT_FPAFF
  47
  48 /*
  49  * Handle the scheduler resume end of FPU affinity management.  We do this
  50  * inline to try to keep the overhead down. If we have been forced to run on
  51  * a "CPU" with an FPU because of a previous high level of FP computation,
  52  * but did not actually use the FPU during the most recent time-slice (CU1
  53  * isn't set), we undo the restriction on cpus_allowed.
  54  *
  55  * We're not calling set_cpus_allowed() here, because we have no need to
  56  * force prompt migration - we're already switching the current CPU to a
  57  * different thread.
  58  */
  59
  60 #define __mips_mt_fpaff_switch_to(prev)                                 \
  61 do {                                                                    \
  62         struct thread_info *__prev_ti = task_thread_info(prev);         \
  63                                                                         \
  64         if (cpu_has_fpu &&                                              \
  65             test_ti_thread_flag(__prev_ti, TIF_FPUBOUND) &&             \
  66             (!(KSTK_STATUS(prev) & ST0_CU1))) {                         \
  67                 clear_ti_thread_flag(__prev_ti, TIF_FPUBOUND);          \
  68                 prev->cpus_allowed = prev->thread.user_cpus_allowed;    \
  69         }                                                               \
  70         next->thread.emulated_fp = 0;                                   \
  71 } while(0)
  72
  73 #else
  74 #define __mips_mt_fpaff_switch_to(prev) do { (void) (prev); } while (0)
  75 #endif
  76
  77 #define __clear_software_ll_bit()                                       \
  78 do {    if (cpu_has_rw_llb) {                                           \
  79                 write_c0_lladdr(0);                                     \
  80         } else {                                                        \
  81                 if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)\
  82                         ll_bit = 0;                                     \
  83         }                                                               \
  84 } while (0)
  85
  86 /*
  87  * For newly created kernel threads switch_to() will return to
  88  * ret_from_kernel_thread, newly created user threads to ret_from_fork.
  89  * That is, everything following resume() will be skipped for new threads.
  90  * So everything that matters to new threads should be placed before resume().
  91  */
  92 #define switch_to(prev, next, last)                                     \
  93 do {                                                                    \
  94         s32 __fpsave = FP_SAVE_NONE;                                    \
  95         __mips_mt_fpaff_switch_to(prev);                                \
  96         if (cpu_has_dsp) {                                              \
  97                 __save_dsp(prev);                                       \
  98                 __restore_dsp(next);                                    \
  99         }                                                               \
 100         if (cop2_present) {                                             \
 101                 set_c0_status(ST0_CU2);                                 \
 102                 if ((KSTK_STATUS(prev) & ST0_CU2)) {                    \
 103                         if (cop2_lazy_restore)                          \
 104                                 KSTK_STATUS(prev) &= ~ST0_CU2;          \
 105                         cop2_save(prev);                                \
 106                 }                                                       \
 107                 if (KSTK_STATUS(next) & ST0_CU2 &&                      \
 108                     !cop2_lazy_restore) {                               \
 109                         cop2_restore(next);                             \
 110                 }                                                       \
 111                 clear_c0_status(ST0_CU2);                               \
 112         }                                                               \
 113         __clear_software_ll_bit();                                      \
 114         if (test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU))          \
 115                 __fpsave = FP_SAVE_SCALAR;                              \
 116         if (test_and_clear_tsk_thread_flag(prev, TIF_USEDMSA))          \
 117                 __fpsave = FP_SAVE_VECTOR;                              \
 118         if (cpu_has_userlocal)                                          \
 119                 write_c0_userlocal(task_thread_info(next)->tp_value);   \
 120         __restore_watch();                                              \
 121         disable_msa();                                                  \
 122         (last) = resume(prev, next, task_thread_info(next), __fpsave);  \
 123 } while (0)
 124
 125 #endif /* _ASM_SWITCH_TO_H */