xref: /openbmc/linux/arch/arm/common/mcpm_head.S (revision f7777dcc) 
1/*
2 * arch/arm/common/mcpm_head.S -- kernel entry point for multi-cluster PM
3 *
4 * Created by:  Nicolas Pitre, March 2012
5 * Copyright:   (C) 2012-2013  Linaro Limited
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 *
12 * Refer to Documentation/arm/cluster-pm-race-avoidance.txt
13 * for details of the synchronisation algorithms used here.
14 */
15
16#include <linux/linkage.h>
17#include <asm/mcpm.h>
18
19#include "vlock.h"
20
21.if MCPM_SYNC_CLUSTER_CPUS
22.error "cpus must be the first member of struct mcpm_sync_struct"
23.endif
24
25	.macro	pr_dbg	string
26#if defined(CONFIG_DEBUG_LL) && defined(DEBUG)
27	b	1901f
281902:	.asciz	"CPU"
291903:	.asciz	" cluster"
301904:	.asciz	": \string"
31	.align
321901:	adr	r0, 1902b
33	bl	printascii
34	mov	r0, r9
35	bl	printhex2
36	adr	r0, 1903b
37	bl	printascii
38	mov	r0, r10
39	bl	printhex2
40	adr	r0, 1904b
41	bl	printascii
42#endif
43	.endm
44
45	.arm
46	.align
47
48ENTRY(mcpm_entry_point)
49
50 THUMB(	adr	r12, BSYM(1f)	)
51 THUMB(	bx	r12		)
52 THUMB(	.thumb			)
531:
54	mrc	p15, 0, r0, c0, c0, 5		@ MPIDR
55	ubfx	r9, r0, #0, #8			@ r9 = cpu
56	ubfx	r10, r0, #8, #8			@ r10 = cluster
57	mov	r3, #MAX_CPUS_PER_CLUSTER
58	mla	r4, r3, r10, r9			@ r4 = canonical CPU index
59	cmp	r4, #(MAX_CPUS_PER_CLUSTER * MAX_NR_CLUSTERS)
60	blo	2f
61
62	/* We didn't expect this CPU.  Try to cheaply make it quiet. */
631:	wfi
64	wfe
65	b	1b
66
672:	pr_dbg	"kernel mcpm_entry_point\n"
68
69	/*
70	 * MMU is off so we need to get to various variables in a
71	 * position independent way.
72	 */
73	adr	r5, 3f
74	ldmia	r5, {r6, r7, r8, r11}
75	add	r6, r5, r6			@ r6 = mcpm_entry_vectors
76	ldr	r7, [r5, r7]			@ r7 = mcpm_power_up_setup_phys
77	add	r8, r5, r8			@ r8 = mcpm_sync
78	add	r11, r5, r11			@ r11 = first_man_locks
79
80	mov	r0, #MCPM_SYNC_CLUSTER_SIZE
81	mla	r8, r0, r10, r8			@ r8 = sync cluster base
82
83	@ Signal that this CPU is coming UP:
84	mov	r0, #CPU_COMING_UP
85	mov	r5, #MCPM_SYNC_CPU_SIZE
86	mla	r5, r9, r5, r8			@ r5 = sync cpu address
87	strb	r0, [r5]
88
89	@ At this point, the cluster cannot unexpectedly enter the GOING_DOWN
90	@ state, because there is at least one active CPU (this CPU).
91
92	mov	r0, #VLOCK_SIZE
93	mla	r11, r0, r10, r11		@ r11 = cluster first man lock
94	mov	r0, r11
95	mov	r1, r9				@ cpu
96	bl	vlock_trylock			@ implies DMB
97
98	cmp	r0, #0				@ failed to get the lock?
99	bne	mcpm_setup_wait		@ wait for cluster setup if so
100
101	ldrb	r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
102	cmp	r0, #CLUSTER_UP			@ cluster already up?
103	bne	mcpm_setup			@ if not, set up the cluster
104
105	@ Otherwise, release the first man lock and skip setup:
106	mov	r0, r11
107	bl	vlock_unlock
108	b	mcpm_setup_complete
109
110mcpm_setup:
111	@ Control dependency implies strb not observable before previous ldrb.
112
113	@ Signal that the cluster is being brought up:
114	mov	r0, #INBOUND_COMING_UP
115	strb	r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND]
116	dmb
117
118	@ Any CPU trying to take the cluster into CLUSTER_GOING_DOWN from this
119	@ point onwards will observe INBOUND_COMING_UP and abort.
120
121	@ Wait for any previously-pending cluster teardown operations to abort
122	@ or complete:
123mcpm_teardown_wait:
124	ldrb	r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
125	cmp	r0, #CLUSTER_GOING_DOWN
126	bne	first_man_setup
127	wfe
128	b	mcpm_teardown_wait
129
130first_man_setup:
131	dmb
132
133	@ If the outbound gave up before teardown started, skip cluster setup:
134
135	cmp	r0, #CLUSTER_UP
136	beq	mcpm_setup_leave
137
138	@ power_up_setup is now responsible for setting up the cluster:
139
140	cmp	r7, #0
141	mov	r0, #1		@ second (cluster) affinity level
142	blxne	r7		@ Call power_up_setup if defined
143	dmb
144
145	mov	r0, #CLUSTER_UP
146	strb	r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
147	dmb
148
149mcpm_setup_leave:
150	@ Leave the cluster setup critical section:
151
152	mov	r0, #INBOUND_NOT_COMING_UP
153	strb	r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND]
154	dsb	st
155	sev
156
157	mov	r0, r11
158	bl	vlock_unlock	@ implies DMB
159	b	mcpm_setup_complete
160
161	@ In the contended case, non-first men wait here for cluster setup
162	@ to complete:
163mcpm_setup_wait:
164	ldrb	r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
165	cmp	r0, #CLUSTER_UP
166	wfene
167	bne	mcpm_setup_wait
168	dmb
169
170mcpm_setup_complete:
171	@ If a platform-specific CPU setup hook is needed, it is
172	@ called from here.
173
174	cmp	r7, #0
175	mov	r0, #0		@ first (CPU) affinity level
176	blxne	r7		@ Call power_up_setup if defined
177	dmb
178
179	@ Mark the CPU as up:
180
181	mov	r0, #CPU_UP
182	strb	r0, [r5]
183
184	@ Observability order of CPU_UP and opening of the gate does not matter.
185
186mcpm_entry_gated:
187	ldr	r5, [r6, r4, lsl #2]		@ r5 = CPU entry vector
188	cmp	r5, #0
189	wfeeq
190	beq	mcpm_entry_gated
191	dmb
192
193	pr_dbg	"released\n"
194	bx	r5
195
196	.align	2
197
1983:	.word	mcpm_entry_vectors - .
199	.word	mcpm_power_up_setup_phys - 3b
200	.word	mcpm_sync - 3b
201	.word	first_man_locks - 3b
202
203ENDPROC(mcpm_entry_point)
204
205	.bss
206
207	.align	CACHE_WRITEBACK_ORDER
208	.type	first_man_locks, #object
209first_man_locks:
210	.space	VLOCK_SIZE * MAX_NR_CLUSTERS
211	.align	CACHE_WRITEBACK_ORDER
212
213	.type	mcpm_entry_vectors, #object
214ENTRY(mcpm_entry_vectors)
215	.space	4 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER
216
217	.type	mcpm_power_up_setup_phys, #object
218ENTRY(mcpm_power_up_setup_phys)
219	.space  4		@ set by mcpm_sync_init()
220