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reset.S @ 1023

Last change on this file since 1023 was 949, checked in by cfuguet, 10 years ago
preloader: when loading LINUX, copy the DTB in low memory addresses
File size: 7.3 KB

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1	/*
2	* \file : reset.S
3	* \date : 01/12/2012
4	* \author: Cesar FUGUET & Manuel BOUYER & Alain Greiner
5	*
6	* This is a generic reset code for a generic multi-clusters / multi-processors
7	* TSAR architecture (up to 256 clusters / up to 4 processors per cluster).
8	*
9	* There is one XICU, one TTY, one DMA, and one memory bank per cluster.
10	*
11	* This preloader uses a stack segment allocated in cluster 0 for processor 0.
12	* The stack allocation is not performed for other processors as they do not
13	* need it during the preloader execution. Therefore, this allocation should be
14	* done by the loaded Operating System.
15	*
16	* The replicated XICU is used to awake the sleeping processors:
17	* xicu_paddr_base = ICU_PADDR_BASE + (cluster_xy << 32)
18	*
19	* It is intended to be used with various operating systems or nano kernels,
20	* including NetBSD, Linux, ALMOS, and GIET_VM.
21	*
22	* - Each processor initializes its Status Register (SR) to disable interrupts.
23	* - Each processor initializes its Count Register.
24	* - Each processor initialises its private XICU WTI mask register.
25	* - Only processor 0 executes the reset_load_elf function to load into memory
26	* the system specific boot-loader stored on disk at RESET_LOADER_LBA
27	* - All other processors wait in a low power consumption mode that the
28	* processor 0 wakes them using an IPI (Inter Processor Interruption)
29	*/
30
31	#include <defs.h>
32	#include <mips32_registers.h>
33
34	/* These define should be consistent with values defined in map.xml file */
35
36	.section .reset,"ax",@progbits
37
38	.extern reset_putc
39	.extern reset_getc
40	.extern reset_ioc_read
41	.extern reset_elf_loader
42	.extern memcpy
43	.extern reset_puts
44	.extern reset_putx
45	.extern reset_putd
46	.extern reset_ioc_init
47	.extern versionstr
48	.extern dtb_start
49	.extern dtb_addr
50
51	.globl reset /* Makes reset an external symbol */
52	.ent reset
53
54	.align 2
55	.set noreorder
56
57	reset:
58	b _reset /* 0xbfc0000 */
59	nop /* 0xbfc0004 */
60
61	/* Addresses of the functions provided by this reset code */
62
63	preloader_vector:
64	.word RESET_VERSION /* 0xbfc0008 */
65	.word dtb_start /* 0xbfc000c */
66	.word reset_putc /* 0xbfc0010 */
67	.word reset_getc /* 0xbfc0014 */
68	.word reset_ioc_read /* 0xbfc0018 */
69	.word reset_elf_loader /* 0xbfc001C */
70	.word memcpy /* 0xbfc0020 */
71	.word reset_puts /* 0xbfc0024 */
72	.word reset_putx /* 0xbfc0028 */
73	.word reset_putd /* 0xbfc002C */
74
75	_reset:
76
77	/* All processors Disable interruptions, keep STATUSbev enabled */
78
79	li k0, (1 << 22)
80	mtc0 k0, CP0_STATUS
81
82	/*
83	* All processors compute gpid, lpid, cluster_xy
84	* gpid = ebase[11:0] = X_WIDTH : Y_WIDTH : P_WIDTH
85	* x y lpid
86	* X, Y and LPID fields are left-aligned
87	*/
88
89	mfc0 k0, CP0_EBASE
90	andi t0, k0, 0xFFF /* t0 <= gpid (<= 4096 procs) */
91	andi t1, t0, ((1<<P_WIDTH)-1) /* t1 <= lpid */
92	srl t2, t0, P_WIDTH /* t2 <= cluster_xy */
93
94	/* All processors initialise the count register in CP0 */
95
96	mtc0 zero, CP0_COUNT
97
98	/*
99	* All processors enable the WTI for XICU
100	* Each processor may have IRQ_PER_PROC irq outputs from the XICU
101	* In each cluster, the XICU base address depends on the cluster_xy
102	*/
103
104	la t3, SEG_XCU_BASE /* t3 <= ICU base address */
105	move t4, t1 /* t4 <= local_id */
106	li t5, IRQ_PER_PROCESSOR /* t5 <= IRQ_PER_PROCESSOR */
107	multu t4, t5
108	mflo t6 /* t6 <= IRQ_PER_PROC * local_id */
109	sll t4, t6, 2 /* t4 <= OUT_INDEX = t6 * 4 */
110
111	li t5, (0xC << 7) /* t5 <= FUNC = XICU_MSK_WTI */
112	or t4, t4, t5 /* t4 <= FUNC \| INDEX \| 00 */
113	or t5, t3, t4 /* t5 <= &XICU[MSK_WTI][OUT_INDEX] */
114
115	/* All processors set WTI mask using the physical address extension */
116
117	li t4, 1
118	sllv t4, t4, t1 /* Set XICU[MSK_WTI][INDEX][local_id] */
119
120	mtc2 t2, CP2_PADDR_EXT /* set PADDR extension */
121	sw t4, 0(t5) /* XICU[MSK_WTI][INDEX] <= t4 */
122	mtc2 zero, CP2_PADDR_EXT /* reset PADDR extension */
123
124	/*
125	* Only processor 0 in cluster 0 loads and executes the boot-loader
126	* We have:
127	* t0: global pid
128	* t1: local pid
129	* t2: cluster_xy
130	* t3: xicu physical base address in cluster 0
131	*/
132
133	bne zero, t0, _reset_wait
134	nop
135
136	/* Processor 0 initializes stack pointer */
137
138	la k0, _stack
139	li k1, RESET_STACK_SIZE /* k1 <= P0 stack size */
140	addu sp, k0, k1 /* P0 stack from base to (base + size) */
141
142	/* Processor 0 displays version for this reset code */
143
144	la a0, versionstr
145	jal reset_puts
146	nop
147
148	/* Processor 0 initializes the block device */
149
150	jal reset_ioc_init
151	nop
152
153	/*
154	* Processor 0 jumps to the reset_elf_loader routine passing as argument
155	* the block number in which is loaded the .elf file
156	*/
157
158	li a0, RESET_LOADER_LBA
159	jal reset_elf_loader
160	nop
161
162	/*
163	* Processor O jumps to the entry address defined in the .elf file, and
164	* returned by reset_elf_loader function.
165	* First argument is pointer to the preloader function vectors other
166	* function arguments are 0
167	*/
168
169	la a0, preloader_vector
170	lw a1, dtb_addr
171	move a2, zero
172	move a3, zero
173	jr v0
174	nop
175
176	/*
177	* All processor (but processor 0) wait in low power mode until processor 0
178	* wakes them using an IPI.
179	* We have:
180	* t0: global id
181	* t1: local id
182	* t2: cluster id
183	* t3: xicu physical base address in cluster 0
184	*/
185
186	_reset_wait:
187
188	sll t4, t1, 2 /* t4 <= local_id * 4 */
189	addu t5, t4, t3 /* t5 <= &XICU[WTI_REG][local_id] */
190
191	wait
192
193	/*
194	* All other processors, when exiting wait mode, read from XICU the address
195	* to jump.
196	* This address is the boot-loader entry address that has been written in
197	* the mailbox by the IPI sent by processor 0
198	*/
199
200	mtc2 t2, CP2_PADDR_EXT /* set PADDR extension */
201	lw k0, 0(t5) /* k0 <= XICU[WTI_REG][local_id] */
202	mtc2 zero, CP2_PADDR_EXT /* reset PADDR extension */
203
204	jr k0
205	nop
206
207	/* Exception entry point */
208
209	.org 0x0380
210	_excep:
211	mfc0 a0, CP0_STATUS /* first arg is status */
212	mfc0 a1, CP0_CAUSE /* second arg is cause */
213	mfc0 a2, CP0_EPC /* third argc is epc */
214	mfc2 a3, CP2_DBVAR /* fourth argc is dbvar */
215	nop
216	j handle_except
217	nop
218
219	.end reset
220
221	.set reorder
222
223	.section .data
224
225	_stack:
226
227	.space RESET_STACK_SIZE
228
229	/*
230	* vim: tabstop=4 : shiftwidth=4 : expandtab
231	*/

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