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
6 * Copyright (C) 1994, 1995, 1996, 1998, 1999, 2002, 2003 Ralf Baechle
7 * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com)
8 * Copyright (C) 1994, 1995, 1996, by Andreas Busse
9 * Copyright (C) 1999 Silicon Graphics, Inc.
10 * Copyright (C) 2000 MIPS Technologies, Inc.
11 * written by Carsten Langgaard, carstenl@mips.com
13 #include <linux/config.h>
15 #include <asm/cachectl.h>
16 #include <asm/fpregdef.h>
17 #include <asm/mipsregs.h>
18 #include <asm/offset.h>
20 #include <asm/pgtable-bits.h>
21 #include <asm/regdef.h>
22 #include <asm/stackframe.h>
23 #include <asm/thread_info.h>
25 #include <asm/asmmacro.h>
28 * Offset to the current process status flags, the first 32 bytes of the
31 #define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS)
34 * FPU context is saved iff the process has used it's FPU in the current
35 * time slice as indicated by _TIF_USEDFPU. In any case, the CU1 bit for user
36 * space STATUS register should be 0, so that a process *always* starts its
37 * userland with FPU disabled after each context switch.
39 * FPU will be enabled as soon as the process accesses FPU again, through
44 * task_struct *resume(task_struct *prev, task_struct *next,
45 * struct thread_info *next_ti)
49 #ifndef CONFIG_CPU_HAS_LLSC
53 LONG_S t1, THREAD_STATUS(a0)
54 cpu_save_nonscratch a0
55 LONG_S ra, THREAD_REG31(a0)
58 * check if we need to save FPU registers
60 PTR_L t3, TASK_THREAD_INFO(a0)
61 LONG_L t0, TI_FLAGS(t3)
68 LONG_S t0, TI_FLAGS(t3)
71 * clear saved user stack CU1 bit
79 fpu_save_double a0 t0 # clobbers t0
84 sdc1 $f0, (THREAD_FPU + 0x00)(a0)
87 fpu_save_16even a0 t1 # clobbers t1
92 * The order of restoring the registers takes care of the race
93 * updating $28, $29 and kernelsp without disabling ints.
96 cpu_restore_nonscratch a1
98 PTR_ADDIU t0, $28, _THREAD_SIZE - 32
99 set_saved_sp t0, t1, t2
101 mfc0 t1, CP0_STATUS /* Do we really need this? */
104 LONG_L a2, THREAD_STATUS(a1)
114 * Save a thread's fp context.
118 fpu_save_double a0 t1 # clobbers t1
123 bgez t1, 1f # 16 register mode?
126 fpu_save_16even a0 t1 # clobbers t1
127 sdc1 $f0, (THREAD_FPU + 0x00)(a0)
133 * Restore a thread's fp context.
137 fpu_restore_double a0, t1 # clobbers t1
142 bgez t1, 1f # 16 register mode?
145 1: fpu_restore_16even a0, t0 # clobbers t0
146 ldc1 $f0, (THREAD_FPU + 0x00)(a0)
153 * Load the FPU with signalling NANS. This bit pattern we're using has
154 * the property that no matter whether considered as single or as double
155 * precision represents signaling NANS.
157 * We initialize fcr31 to rounding to nearest, no exceptions.
160 #define FPU_DEFAULT 0x00000000
176 bgez t0, 1f # 16 / 32 register mode?
197 #ifdef CONFIG_CPU_MIPS32