1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Early kernel startup code for Hexagon
4 *
5 * Copyright (c) 2010-2013, The Linux Foundation. All rights reserved.
6 */
7
8#include <linux/linkage.h>
9#include <linux/init.h>
10#include <asm/asm-offsets.h>
11#include <asm/mem-layout.h>
12#include <asm/vm_mmu.h>
13#include <asm/page.h>
14#include <asm/hexagon_vm.h>
15
16#define SEGTABLE_ENTRIES #0x0e0
17
18 __INIT
19ENTRY(stext)
20 /*
21 * VMM will already have set up true vector page, MMU, etc.
22 * To set up initial kernel identity map, we have to pass
23 * the VMM a pointer to some canonical page tables. In
24 * this implementation, we're assuming that we've got
25 * them precompiled. Generate value in R24, as we'll need
26 * it again shortly.
27 */
28 r24.L = #LO(swapper_pg_dir)
29 r24.H = #HI(swapper_pg_dir)
30
31 /*
32 * Symbol is kernel segment address, but we need
33 * the logical/physical address.
34 */
35 r25 = pc;
36 r2.h = #0xffc0;
37 r2.l = #0x0000;
38 r25 = and(r2,r25); /* R25 holds PHYS_OFFSET now */
39 r1.h = #HI(PAGE_OFFSET);
40 r1.l = #LO(PAGE_OFFSET);
41 r24 = sub(r24,r1); /* swapper_pg_dir - PAGE_OFFSET */
42 r24 = add(r24,r25); /* + PHYS_OFFSET */
43
44 r0 = r24; /* aka __pa(swapper_pg_dir) */
45
46 /*
47 * Initialize page dir to make the virtual and physical
48 * addresses where the kernel was loaded be identical.
49 * Done in 4MB chunks.
50 */
51#define PTE_BITS ( __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X \
52 | __HEXAGON_C_WB_L2 << 6 \
53 | __HVM_PDE_S_4MB)
54
55 /*
56 * Get number of VA=PA entries; only really needed for jump
57 * to hyperspace; gets blown away immediately after
58 */
59
60 {
61 r1.l = #LO(_end);
62 r2.l = #LO(stext);
63 r3 = #1;
64 }
65 {
66 r1.h = #HI(_end);
67 r2.h = #HI(stext);
68 r3 = asl(r3, #22);
69 }
70 {
71 r1 = sub(r1, r2);
72 r3 = add(r3, #-1);
73 } /* r1 = _end - stext */
74 r1 = add(r1, r3); /* + (4M-1) */
75 r26 = lsr(r1, #22); /* / 4M = # of entries */
76
77 r1 = r25;
78 r2.h = #0xffc0;
79 r2.l = #0x0000; /* round back down to 4MB boundary */
80 r1 = and(r1,r2);
81 r2 = lsr(r1, #22) /* 4MB page number */
82 r2 = asl(r2, #2) /* times sizeof(PTE) (4bytes) */
83 r0 = add(r0,r2) /* r0 = address of correct PTE */
84 r2 = #PTE_BITS
85 r1 = add(r1,r2) /* r1 = 4MB PTE for the first entry */
86 r2.h = #0x0040
87 r2.l = #0x0000 /* 4MB increments */
88 loop0(1f,r26);
891:
90 memw(r0 ++ #4) = r1
91 { r1 = add(r1, r2); } :endloop0
92
93 /* Also need to overwrite the initial 0xc0000000 entries */
94 /* PAGE_OFFSET >> (4MB shift - 4 bytes per entry shift) */
95 R1.H = #HI(PAGE_OFFSET >> (22 - 2))
96 R1.L = #LO(PAGE_OFFSET >> (22 - 2))
97
98 r0 = add(r1, r24); /* advance to 0xc0000000 entry */
99 r1 = r25;
100 r2.h = #0xffc0;
101 r2.l = #0x0000; /* round back down to 4MB boundary */
102 r1 = and(r1,r2); /* for huge page */
103 r2 = #PTE_BITS
104 r1 = add(r1,r2);
105 r2.h = #0x0040
106 r2.l = #0x0000 /* 4MB increments */
107
108 loop0(1f,SEGTABLE_ENTRIES);
1091:
110 memw(r0 ++ #4) = r1;
111 { r1 = add(r1,r2); } :endloop0
112
113 r0 = r24;
114
115 /*
116 * The subroutine wrapper around the virtual instruction touches
117 * no memory, so we should be able to use it even here.
118 * Note that in this version, R1 and R2 get "clobbered"; see
119 * vm_ops.S
120 */
121 r1 = #VM_TRANS_TYPE_TABLE
122 call __vmnewmap;
123
124 /* Jump into virtual address range. */
125
126 r31.h = #hi(__head_s_vaddr_target)
127 r31.l = #lo(__head_s_vaddr_target)
128 jumpr r31
129
130 /* Insert trippy space effects. */
131
132__head_s_vaddr_target:
133 /*
134 * Tear down VA=PA translation now that we are running
135 * in kernel virtual space.
136 */
137 r0 = #__HVM_PDE_S_INVALID
138
139 r1.h = #0xffc0;
140 r1.l = #0x0000;
141 r2 = r25; /* phys_offset */
142 r2 = and(r1,r2);
143
144 r1.l = #lo(swapper_pg_dir)
145 r1.h = #hi(swapper_pg_dir)
146 r2 = lsr(r2, #22) /* 4MB page number */
147 r2 = asl(r2, #2) /* times sizeof(PTE) (4bytes) */
148 r1 = add(r1,r2);
149 loop0(1f,r26)
150
1511:
152 {
153 memw(R1 ++ #4) = R0
154 }:endloop0
155
156 r0 = r24
157 r1 = #VM_TRANS_TYPE_TABLE
158 call __vmnewmap
159
160 /* Go ahead and install the trap0 return so angel calls work */
161 r0.h = #hi(_K_provisional_vec)
162 r0.l = #lo(_K_provisional_vec)
163 call __vmsetvec
164
165 /*
166 * OK, at this point we should start to be much more careful,
167 * we're going to enter C code and start touching memory
168 * in all sorts of places.
169 * This means:
170 * SGP needs to be OK
171 * Need to lock shared resources
172 * A bunch of other things that will cause
173 * all kinds of painful bugs
174 */
175
176 /*
177 * Stack pointer should be pointed at the init task's
178 * thread stack, which should have been declared in arch/init_task.c.
179 * So uhhhhh...
180 * It's accessible via the init_thread_union, which is a union
181 * of a thread_info struct and a stack; of course, the top
182 * of the stack is not for you. The end of the stack
183 * is simply init_thread_union + THREAD_SIZE.
184 */
185
186 {r29.H = #HI(init_thread_union); r0.H = #HI(_THREAD_SIZE); }
187 {r29.L = #LO(init_thread_union); r0.L = #LO(_THREAD_SIZE); }
188
189 /* initialize the register used to point to current_thread_info */
190 /* Fixme: THREADINFO_REG can't be R2 because of that memset thing. */
191 {r29 = add(r29,r0); THREADINFO_REG = r29; }
192
193 /* Hack: zero bss; */
194 { r0.L = #LO(__bss_start); r1 = #0; r2.l = #LO(__bss_stop); }
195 { r0.H = #HI(__bss_start); r2.h = #HI(__bss_stop); }
196
197 r2 = sub(r2,r0);
198 call memset;
199
200 /* Set PHYS_OFFSET; should be in R25 */
201#ifdef CONFIG_HEXAGON_PHYS_OFFSET
202 r0.l = #LO(__phys_offset);
203 r0.h = #HI(__phys_offset);
204 memw(r0) = r25;
205#endif
206
207 /* Time to make the doughnuts. */
208 call start_kernel
209
210 /*
211 * Should not reach here.
212 */
2131:
214 jump 1b
215
216.p2align PAGE_SHIFT
217ENTRY(external_cmdline_buffer)
218 .fill _PAGE_SIZE,1,0
219
220.data
221.p2align PAGE_SHIFT
222ENTRY(empty_zero_page)
223 .fill _PAGE_SIZE,1,0
224

source code of linux/arch/hexagon/kernel/head.S