xref: /linux/arch/hexagon/kernel/head.S (revision 4b132aacb0768ac1e652cf517097ea6f237214b9)
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