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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 | * -"C" version of lowest level context switch asm macro called by schedular | |
10 | * gcc doesn't generate the dward CFI info for hand written asm, hence can't | |
11 | * backtrace out of it (e.g. tasks sleeping in kernel). | |
12 | * So we cheat a bit by writing almost similar code in inline-asm. | |
13 | * -This is a hacky way of doing things, but there is no other simple way. | |
14 | * I don't want/intend to extend unwinding code to understand raw asm | |
15 | */ | |
16 | ||
17 | #include <asm/asm-offsets.h> | |
18 | #include <linux/sched.h> | |
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19 | #ifdef CONFIG_ARC_PLAT_EZNPS |
20 | #include <plat/ctop.h> | |
21 | #endif | |
bf90e1ea | 22 | |
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23 | #define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4) |
24 | ||
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25 | struct task_struct *__sched |
26 | __switch_to(struct task_struct *prev_task, struct task_struct *next_task) | |
27 | { | |
28 | unsigned int tmp; | |
29 | unsigned int prev = (unsigned int)prev_task; | |
30 | unsigned int next = (unsigned int)next_task; | |
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31 | |
32 | __asm__ __volatile__( | |
33 | /* FP/BLINK save generated by gcc (standard function prologue */ | |
34 | "st.a r13, [sp, -4] \n\t" | |
35 | "st.a r14, [sp, -4] \n\t" | |
36 | "st.a r15, [sp, -4] \n\t" | |
37 | "st.a r16, [sp, -4] \n\t" | |
38 | "st.a r17, [sp, -4] \n\t" | |
39 | "st.a r18, [sp, -4] \n\t" | |
40 | "st.a r19, [sp, -4] \n\t" | |
41 | "st.a r20, [sp, -4] \n\t" | |
42 | "st.a r21, [sp, -4] \n\t" | |
43 | "st.a r22, [sp, -4] \n\t" | |
44 | "st.a r23, [sp, -4] \n\t" | |
45 | "st.a r24, [sp, -4] \n\t" | |
080c3747 | 46 | #ifndef CONFIG_ARC_CURR_IN_REG |
bf90e1ea | 47 | "st.a r25, [sp, -4] \n\t" |
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48 | #else |
49 | "sub sp, sp, 4 \n\t" /* usual r25 placeholder */ | |
080c3747 | 50 | #endif |
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51 | |
52 | /* set ksp of outgoing task in tsk->thread.ksp */ | |
57e26e57 | 53 | #if KSP_WORD_OFF <= 255 |
bf90e1ea | 54 | "st.as sp, [%3, %1] \n\t" |
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55 | #else |
56 | /* | |
57 | * Workaround for NR_CPUS=4k | |
58 | * %1 is bigger than 255 (S9 offset for st.as) | |
59 | */ | |
60 | "add2 r24, %3, %1 \n\t" | |
61 | "st sp, [r24] \n\t" | |
62 | #endif | |
bf90e1ea | 63 | |
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64 | /* |
65 | * setup _current_task with incoming tsk. | |
66 | * optionally, set r25 to that as well | |
67 | * For SMP extra work to get to &_current_task[cpu] | |
68 | * (open coded SET_CURR_TASK_ON_CPU) | |
69 | */ | |
41195d23 | 70 | #ifndef CONFIG_SMP |
bf90e1ea | 71 | "st %2, [@_current_task] \n\t" |
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72 | #else |
73 | #ifdef CONFIG_ARC_PLAT_EZNPS | |
74 | "lr r24, [%4] \n\t" | |
75 | #ifndef CONFIG_EZNPS_MTM_EXT | |
76 | "lsr r24, r24, 4 \n\t" | |
77 | #endif | |
41195d23 VG |
78 | #else |
79 | "lr r24, [identity] \n\t" | |
80 | "lsr r24, r24, 8 \n\t" | |
81 | "bmsk r24, r24, 7 \n\t" | |
86c25466 | 82 | #endif |
41195d23 VG |
83 | "add2 r24, @_current_task, r24 \n\t" |
84 | "st %2, [r24] \n\t" | |
85 | #endif | |
86 | #ifdef CONFIG_ARC_CURR_IN_REG | |
87 | "mov r25, %2 \n\t" | |
88 | #endif | |
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89 | |
90 | /* get ksp of incoming task from tsk->thread.ksp */ | |
91 | "ld.as sp, [%2, %1] \n\t" | |
92 | ||
93 | /* start loading it's CALLEE reg file */ | |
94 | ||
080c3747 | 95 | #ifndef CONFIG_ARC_CURR_IN_REG |
bf90e1ea | 96 | "ld.ab r25, [sp, 4] \n\t" |
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97 | #else |
98 | "add sp, sp, 4 \n\t" | |
080c3747 | 99 | #endif |
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100 | "ld.ab r24, [sp, 4] \n\t" |
101 | "ld.ab r23, [sp, 4] \n\t" | |
102 | "ld.ab r22, [sp, 4] \n\t" | |
103 | "ld.ab r21, [sp, 4] \n\t" | |
104 | "ld.ab r20, [sp, 4] \n\t" | |
105 | "ld.ab r19, [sp, 4] \n\t" | |
106 | "ld.ab r18, [sp, 4] \n\t" | |
107 | "ld.ab r17, [sp, 4] \n\t" | |
108 | "ld.ab r16, [sp, 4] \n\t" | |
109 | "ld.ab r15, [sp, 4] \n\t" | |
110 | "ld.ab r14, [sp, 4] \n\t" | |
111 | "ld.ab r13, [sp, 4] \n\t" | |
112 | ||
113 | /* last (ret value) = prev : although for ARC it mov r0, r0 */ | |
114 | "mov %0, %3 \n\t" | |
115 | ||
116 | /* FP/BLINK restore generated by gcc (standard func epilogue */ | |
117 | ||
118 | : "=r"(tmp) | |
57e26e57 | 119 | : "n"(KSP_WORD_OFF), "r"(next), "r"(prev) |
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120 | #ifdef CONFIG_ARC_PLAT_EZNPS |
121 | , "i"(CTOP_AUX_LOGIC_GLOBAL_ID) | |
122 | #endif | |
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123 | : "blink" |
124 | ); | |
125 | ||
126 | return (struct task_struct *)tmp; | |
127 | } |