1/* 2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 * 8 * Vineetg: Aug 2009 9 * -Moved core context switch macro out of entry.S into this file. 10 * -This is the more "natural" hand written assembler 11 */ 12 13#include <linux/linkage.h> 14#include <asm/entry.h> /* For the SAVE_* macros */ 15#include <asm/asm-offsets.h> 16 17#define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4) 18 19;################### Low Level Context Switch ########################## 20 21 .section .sched.text,"ax",@progbits 22 .align 4 23 .global __switch_to 24 .type __switch_to, @function 25__switch_to: 26 27 /* Save regs on kernel mode stack of task */ 28 st.a blink, [sp, -4] 29 st.a fp, [sp, -4] 30 SAVE_CALLEE_SAVED_KERNEL 31 32 /* Save the now KSP in task->thread.ksp */ 33#if KSP_WORD_OFF <= 255 34 st.as sp, [r0, KSP_WORD_OFF] 35#else 36 /* Workaround for NR_CPUS=4k as ST.as can only take s9 offset */ 37 add2 r24, r0, KSP_WORD_OFF 38 st sp, [r24] 39#endif 40 /* 41 * Return last task in r0 (return reg) 42 * On ARC, Return reg = First Arg reg = r0. 43 * Since we already have last task in r0, 44 * don't need to do anything special to return it 45 */ 46 47 /* hardware memory barrier */ 48 sync 49 50 /* 51 * switch to new task, contained in r1 52 * Temp reg r3 is required to get the ptr to store val 53 */ 54 SET_CURR_TASK_ON_CPU r1, r3 55 56 /* reload SP with kernel mode stack pointer in task->thread.ksp */ 57 ld.as sp, [r1, (TASK_THREAD + THREAD_KSP)/4] 58 59 /* restore the registers */ 60 RESTORE_CALLEE_SAVED_KERNEL 61 ld.ab fp, [sp, 4] 62 ld.ab blink, [sp, 4] 63 j [blink] 64 65END(__switch_to) 66