1 /*
2  * Spin Table SMP initialisation
3  *
4  * Copyright (C) 2013 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 
19 #include <linux/delay.h>
20 #include <linux/init.h>
21 #include <linux/of.h>
22 #include <linux/smp.h>
23 
24 #include <asm/cacheflush.h>
25 #include <asm/cpu_ops.h>
26 #include <asm/cputype.h>
27 #include <asm/smp_plat.h>
28 
29 extern void secondary_holding_pen(void);
30 volatile unsigned long secondary_holding_pen_release = INVALID_HWID;
31 
32 static phys_addr_t cpu_release_addr[NR_CPUS];
33 
34 /*
35  * Write secondary_holding_pen_release in a way that is guaranteed to be
36  * visible to all observers, irrespective of whether they're taking part
37  * in coherency or not.  This is necessary for the hotplug code to work
38  * reliably.
39  */
40 static void write_pen_release(u64 val)
41 {
42 	void *start = (void *)&secondary_holding_pen_release;
43 	unsigned long size = sizeof(secondary_holding_pen_release);
44 
45 	secondary_holding_pen_release = val;
46 	__flush_dcache_area(start, size);
47 }
48 
49 
50 static int smp_spin_table_cpu_init(struct device_node *dn, unsigned int cpu)
51 {
52 	/*
53 	 * Determine the address from which the CPU is polling.
54 	 */
55 	if (of_property_read_u64(dn, "cpu-release-addr",
56 				 &cpu_release_addr[cpu])) {
57 		pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
58 		       cpu);
59 
60 		return -1;
61 	}
62 
63 	return 0;
64 }
65 
66 static int smp_spin_table_cpu_prepare(unsigned int cpu)
67 {
68 	void **release_addr;
69 
70 	if (!cpu_release_addr[cpu])
71 		return -ENODEV;
72 
73 	release_addr = __va(cpu_release_addr[cpu]);
74 
75 	/*
76 	 * We write the release address as LE regardless of the native
77 	 * endianess of the kernel. Therefore, any boot-loaders that
78 	 * read this address need to convert this address to the
79 	 * boot-loader's endianess before jumping. This is mandated by
80 	 * the boot protocol.
81 	 */
82 	release_addr[0] = (void *) cpu_to_le64(__pa(secondary_holding_pen));
83 
84 	__flush_dcache_area(release_addr, sizeof(release_addr[0]));
85 
86 	/*
87 	 * Send an event to wake up the secondary CPU.
88 	 */
89 	sev();
90 
91 	return 0;
92 }
93 
94 static int smp_spin_table_cpu_boot(unsigned int cpu)
95 {
96 	/*
97 	 * Update the pen release flag.
98 	 */
99 	write_pen_release(cpu_logical_map(cpu));
100 
101 	/*
102 	 * Send an event, causing the secondaries to read pen_release.
103 	 */
104 	sev();
105 
106 	return 0;
107 }
108 
109 const struct cpu_operations smp_spin_table_ops = {
110 	.name		= "spin-table",
111 	.cpu_init	= smp_spin_table_cpu_init,
112 	.cpu_prepare	= smp_spin_table_cpu_prepare,
113 	.cpu_boot	= smp_spin_table_cpu_boot,
114 };
115