/* * r2300_switch.S: R2300 specific task switching code. * * Copyright (C) 1994, 1995, 1996, 1999 by Ralf Baechle * Copyright (C) 1994, 1995, 1996 by Andreas Busse * * Multi-cpu abstraction and macros for easier reading: * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com) * * Further modifications to make this work: * Copyright (c) 1998-2000 Harald Koerfgen */ #include <linux/config.h> #include <asm/asm.h> #include <asm/cachectl.h> #include <asm/fpregdef.h> #include <asm/mipsregs.h> #include <asm/asm-offsets.h> #include <asm/page.h> #include <asm/regdef.h> #include <asm/stackframe.h> #include <asm/thread_info.h> #include <asm/asmmacro.h> .set mips1 .align 5 /* * Offset to the current process status flags, the first 32 bytes of the * stack are not used. */ #define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS) /* * FPU context is saved iff the process has used it's FPU in the current * time slice as indicated by TIF_USEDFPU. In any case, the CU1 bit for user * space STATUS register should be 0, so that a process *always* starts its * userland with FPU disabled after each context switch. * * FPU will be enabled as soon as the process accesses FPU again, through * do_cpu() trap. */ /* * task_struct *resume(task_struct *prev, task_struct *next, * struct thread_info *next_ti) ) */ LEAF(resume) #ifndef CONFIG_CPU_HAS_LLSC sw zero, ll_bit #endif mfc0 t1, CP0_STATUS sw t1, THREAD_STATUS(a0) cpu_save_nonscratch a0 sw ra, THREAD_REG31(a0) /* * check if we need to save FPU registers */ lw t3, TASK_THREAD_INFO(a0) lw t0, TI_FLAGS(t3) li t1, _TIF_USEDFPU and t2, t0, t1 beqz t2, 1f nor t1, zero, t1 and t0, t0, t1 sw t0, TI_FLAGS(t3) /* * clear saved user stack CU1 bit */ lw t0, ST_OFF(t3) li t1, ~ST0_CU1 and t0, t0, t1 sw t0, ST_OFF(t3) fpu_save_single a0, t0 # clobbers t0 1: /* * The order of restoring the registers takes care of the race * updating $28, $29 and kernelsp without disabling ints. */ move $28, a2 cpu_restore_nonscratch a1 addiu t1, $28, _THREAD_SIZE - 32 sw t1, kernelsp mfc0 t1, CP0_STATUS /* Do we really need this? */ li a3, 0xff01 and t1, a3 lw a2, THREAD_STATUS(a1) nor a3, $0, a3 and a2, a3 or a2, t1 mtc0 a2, CP0_STATUS move v0, a0 jr ra END(resume) /* * Save a thread's fp context. */ LEAF(_save_fp) fpu_save_single a0, t1 # clobbers t1 jr ra END(_save_fp) /* * Restore a thread's fp context. */ LEAF(_restore_fp) fpu_restore_single a0, t1 # clobbers t1 jr ra END(_restore_fp) /* * Load the FPU with signalling NANS. This bit pattern we're using has * the property that no matter whether considered as single or as double * precision represents signaling NANS. * * We initialize fcr31 to rounding to nearest, no exceptions. */ #define FPU_DEFAULT 0x00000000 LEAF(_init_fpu) mfc0 t0, CP0_STATUS li t1, ST0_CU1 or t0, t1 mtc0 t0, CP0_STATUS li t1, FPU_DEFAULT ctc1 t1, fcr31 li t0, -1 mtc1 t0, $f0 mtc1 t0, $f1 mtc1 t0, $f2 mtc1 t0, $f3 mtc1 t0, $f4 mtc1 t0, $f5 mtc1 t0, $f6 mtc1 t0, $f7 mtc1 t0, $f8 mtc1 t0, $f9 mtc1 t0, $f10 mtc1 t0, $f11 mtc1 t0, $f12 mtc1 t0, $f13 mtc1 t0, $f14 mtc1 t0, $f15 mtc1 t0, $f16 mtc1 t0, $f17 mtc1 t0, $f18 mtc1 t0, $f19 mtc1 t0, $f20 mtc1 t0, $f21 mtc1 t0, $f22 mtc1 t0, $f23 mtc1 t0, $f24 mtc1 t0, $f25 mtc1 t0, $f26 mtc1 t0, $f27 mtc1 t0, $f28 mtc1 t0, $f29 mtc1 t0, $f30 mtc1 t0, $f31 jr ra END(_init_fpu)