summaryrefslogtreecommitdiffstats
path: root/arch/arm64/kernel/smp_spin_table.c
blob: 44c22805d2e2ad7e16895dc248bb9e861105fe07 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
/*
 * Spin Table SMP initialisation
 *
 * Copyright (C) 2013 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/of.h>
#include <linux/smp.h>

#include <asm/cacheflush.h>
#include <asm/cpu_ops.h>
#include <asm/cputype.h>
#include <asm/smp_plat.h>

extern void secondary_holding_pen(void);
volatile unsigned long secondary_holding_pen_release = INVALID_HWID;

static phys_addr_t cpu_release_addr[NR_CPUS];
static DEFINE_RAW_SPINLOCK(boot_lock);

/*
 * Write secondary_holding_pen_release in a way that is guaranteed to be
 * visible to all observers, irrespective of whether they're taking part
 * in coherency or not.  This is necessary for the hotplug code to work
 * reliably.
 */
static void write_pen_release(u64 val)
{
	void *start = (void *)&secondary_holding_pen_release;
	unsigned long size = sizeof(secondary_holding_pen_release);

	secondary_holding_pen_release = val;
	__flush_dcache_area(start, size);
}


static int smp_spin_table_cpu_init(struct device_node *dn, unsigned int cpu)
{
	/*
	 * Determine the address from which the CPU is polling.
	 */
	if (of_property_read_u64(dn, "cpu-release-addr",
				 &cpu_release_addr[cpu])) {
		pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
		       cpu);

		return -1;
	}

	return 0;
}

static int smp_spin_table_cpu_prepare(unsigned int cpu)
{
	void **release_addr;

	if (!cpu_release_addr[cpu])
		return -ENODEV;

	release_addr = __va(cpu_release_addr[cpu]);

	/*
	 * We write the release address as LE regardless of the native
	 * endianess of the kernel. Therefore, any boot-loaders that
	 * read this address need to convert this address to the
	 * boot-loader's endianess before jumping. This is mandated by
	 * the boot protocol.
	 */
	release_addr[0] = (void *) cpu_to_le64(__pa(secondary_holding_pen));

	__flush_dcache_area(release_addr, sizeof(release_addr[0]));

	/*
	 * Send an event to wake up the secondary CPU.
	 */
	sev();

	return 0;
}

static int smp_spin_table_cpu_boot(unsigned int cpu)
{
	unsigned long timeout;

	/*
	 * Set synchronisation state between this boot processor
	 * and the secondary one
	 */
	raw_spin_lock(&boot_lock);

	/*
	 * Update the pen release flag.
	 */
	write_pen_release(cpu_logical_map(cpu));

	/*
	 * Send an event, causing the secondaries to read pen_release.
	 */
	sev();

	timeout = jiffies + (1 * HZ);
	while (time_before(jiffies, timeout)) {
		if (secondary_holding_pen_release == INVALID_HWID)
			break;
		udelay(10);
	}

	/*
	 * Now the secondary core is starting up let it run its
	 * calibrations, then wait for it to finish
	 */
	raw_spin_unlock(&boot_lock);

	return secondary_holding_pen_release != INVALID_HWID ? -ENOSYS : 0;
}

void smp_spin_table_cpu_postboot(void)
{
	/*
	 * Let the primary processor know we're out of the pen.
	 */
	write_pen_release(INVALID_HWID);

	/*
	 * Synchronise with the boot thread.
	 */
	raw_spin_lock(&boot_lock);
	raw_spin_unlock(&boot_lock);
}

const struct cpu_operations smp_spin_table_ops = {
	.name		= "spin-table",
	.cpu_init	= smp_spin_table_cpu_init,
	.cpu_prepare	= smp_spin_table_cpu_prepare,
	.cpu_boot	= smp_spin_table_cpu_boot,
	.cpu_postboot	= smp_spin_table_cpu_postboot,
};
OpenPOWER on IntegriCloud