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e49ee290 RK |
1 | /* |
2 | * Context switch support for Hexagon | |
3 | * | |
e1858b2a | 4 | * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved. |
e49ee290 RK |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 and | |
8 | * only version 2 as published by the Free Software Foundation. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA | |
18 | * 02110-1301, USA. | |
19 | */ | |
20 | ||
21 | #include <asm/asm-offsets.h> | |
22 | ||
23 | .text | |
24 | ||
25 | /* | |
26 | * The register used as a fast-path thread information pointer | |
27 | * is determined as a kernel configuration option. If it happens | |
28 | * to be a callee-save register, we're going to be saving and | |
29 | * restoring it twice here. | |
30 | * | |
31 | * This code anticipates a revised ABI where R20-23 are added | |
32 | * to the set of callee-save registers, but this should be | |
33 | * backward compatible to legacy tools. | |
34 | */ | |
35 | ||
36 | ||
37 | /* | |
38 | * void switch_to(struct task_struct *prev, | |
39 | * struct task_struct *next, struct task_struct *last); | |
40 | */ | |
41 | .p2align 2 | |
42 | .globl __switch_to | |
43 | .type __switch_to, @function | |
44 | ||
45 | /* | |
46 | * When we exit the wormhole, we need to store the previous task | |
47 | * in the new R0's pointer. Technically it should be R2, but they should | |
48 | * be the same; seems like a legacy thing. In short, don't butcher | |
49 | * R0, let it go back out unmolested. | |
50 | */ | |
51 | ||
52 | __switch_to: | |
53 | /* | |
54 | * Push callee-saves onto "prev" stack. | |
55 | * Here, we're sneaky because the LR and FP | |
56 | * storage of the thread_stack structure | |
57 | * is automagically allocated by allocframe, | |
58 | * so we pass struct size less 8. | |
59 | */ | |
60 | allocframe(#(_SWITCH_STACK_SIZE - 8)); | |
61 | memd(R29+#(_SWITCH_R2726))=R27:26; | |
62 | memd(R29+#(_SWITCH_R2524))=R25:24; | |
63 | memd(R29+#(_SWITCH_R2322))=R23:22; | |
64 | memd(R29+#(_SWITCH_R2120))=R21:20; | |
65 | memd(R29+#(_SWITCH_R1918))=R19:18; | |
66 | memd(R29+#(_SWITCH_R1716))=R17:16; | |
67 | /* Stash thread_info pointer in task_struct */ | |
68 | memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG; | |
69 | memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29; | |
70 | /* Switch to "next" stack and restore callee saves from there */ | |
71 | R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)); | |
72 | { | |
73 | R27:26 = memd(R29+#(_SWITCH_R2726)); | |
74 | R25:24 = memd(R29+#(_SWITCH_R2524)); | |
75 | } | |
76 | { | |
77 | R23:22 = memd(R29+#(_SWITCH_R2322)); | |
78 | R21:20 = memd(R29+#(_SWITCH_R2120)); | |
79 | } | |
80 | { | |
81 | R19:18 = memd(R29+#(_SWITCH_R1918)); | |
82 | R17:16 = memd(R29+#(_SWITCH_R1716)); | |
83 | } | |
84 | { | |
85 | /* THREADINFO_REG is currently one of the callee-saved regs | |
86 | * above, and so be sure to re-load it last. | |
87 | */ | |
88 | THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO); | |
89 | R31:30 = memd(R29+#_SWITCH_FP); | |
90 | } | |
91 | { | |
92 | R29 = add(R29,#_SWITCH_STACK_SIZE); | |
93 | jumpr R31; | |
94 | } | |
95 | .size __switch_to, .-__switch_to |